[1/8] gpio: Add Elba SoC gpio driver for spi cs control

This GPIO driver is for the Pensando Elba SoC which
provides control of four chip selects on two SPI busses.

Signed-off-by: Brad Larson <brad@pensando.io>
---
 drivers/gpio/Kconfig           |   6 ++
 drivers/gpio/Makefile          |   1 +
 drivers/gpio/gpio-elba-spics.c | 120 +++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)
 create mode 100644 drivers/gpio/gpio-elba-spics.c

Hi Brad,

thanks for your patch!

On Thu, Mar 4, 2021 at 4:42 AM Brad Larson <brad@pensando.io> wrote:

> This GPIO driver is for the Pensando Elba SoC which
> provides control of four chip selects on two SPI busses.
>
> Signed-off-by: Brad Larson <brad@pensando.io>
(...)

> +#include <linux/gpio.h>

Use this in new drivers:
#include <linux/gpio/driver.h>

> + * pin:             3            2        |       1            0
> + * bit:         7------6------5------4----|---3------2------1------0
> + *     cs1  cs1_ovr  cs0  cs0_ovr |  cs1  cs1_ovr  cs0  cs0_ovr
> + *                ssi1            |             ssi0
> + */
> +#define SPICS_PIN_SHIFT(pin)   (2 * (pin))
> +#define SPICS_MASK(pin)                (0x3 << SPICS_PIN_SHIFT(pin))
> +#define SPICS_SET(pin, val)    ((((val) << 1) | 0x1) << SPICS_PIN_SHIFT(pin))

So 2 bits per GPIO line in one register? (Nice doc!)

> +struct elba_spics_priv {
> +       void __iomem *base;
> +       spinlock_t lock;
> +       struct gpio_chip chip;
> +};
> +
> +static int elba_spics_get_value(struct gpio_chip *chip, unsigned int pin)
> +{
> +       return -ENXIO;
> +}

Write a comment that the chip only supports output mode,
because it repurposes SPI CS pins as generic GPIO out,
maybe at the top of the file?

I suppose these systems also actually (ab)use the SPI cs
for things that are not really SPI CS? Because otherwise
this could just be part of the SPI driver (native chip select).

> +static const struct of_device_id ebla_spics_of_match[] = {
> +       { .compatible = "pensando,elba-spics" },

Have you documented this?

Other than that this is a nice and complete driver.

Yours,
Linus Walleij

> -----Original Message-----
> From: Brad Larson <brad@pensando.io>
> Sent: Wednesday, March 3, 2021 9:42 PM
> Subject: [PATCH 1/8] gpio: Add Elba SoC gpio driver for spi cs control
.
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
...
> +config GPIO_ELBA_SPICS
> +	bool "Pensando Elba SPI chip-select"
> +	depends on ARCH_PENSANDO_ELBA_SOC
> +	help
> +	  Say yes here to support the Pensndo Elba SoC SPI chip-select
> driver

Pensndo should be Pensando

> diff --git a/drivers/gpio/gpio-elba-spics.c b/drivers/gpio/gpio-elba-spics.c
> + * Pensando Elba ASIC SPI chip select driver
...
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Elba SPI chip-select driver");

I think it's conventional to include the company name there, so
start that with "Pensando Elba"

Also, "SoC" and "ASIC" are sometimes included after Elba, but sometimes
are not. Consistency might be helpful.

> +static const struct of_device_id ebla_spics_of_match[] = {
...
> +		.of_match_table = ebla_spics_of_match,

ebla should be elba

On 04/03/2021 04:41, Brad Larson wrote:
> This GPIO driver is for the Pensando Elba SoC which
> provides control of four chip selects on two SPI busses.
> 
> Signed-off-by: Brad Larson <brad@pensando.io>
> ---
>  drivers/gpio/Kconfig           |   6 ++
>  drivers/gpio/Makefile          |   1 +
>  drivers/gpio/gpio-elba-spics.c | 120 +++++++++++++++++++++++++++++++++
>  3 files changed, 127 insertions(+)
>  create mode 100644 drivers/gpio/gpio-elba-spics.c

(...)

> +static int elba_spics_probe(struct platform_device *pdev)
> +{
> +	struct elba_spics_priv *p;
> +	struct resource *res;
> +	int ret;
> +
> +	p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
> +	if (!p)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	p->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(p->base)) {
> +		dev_err(&pdev->dev, "failed to remap I/O memory\n");
> +		return PTR_ERR(p->base);
> +	}
> +	spin_lock_init(&p->lock);
> +	platform_set_drvdata(pdev, p);
> +
> +	p->chip.ngpio = 4;	/* 2 cs pins for spi0, and 2 for spi1 */
> +	p->chip.base = -1;
> +	p->chip.direction_input = elba_spics_direction_input;
> +	p->chip.direction_output = elba_spics_direction_output;
> +	p->chip.get = elba_spics_get_value;
> +	p->chip.set = elba_spics_set_value;
> +	p->chip.label = dev_name(&pdev->dev);
> +	p->chip.parent = &pdev->dev;
> +	p->chip.owner = THIS_MODULE;
> +
> +	ret = devm_gpiochip_add_data(&pdev->dev, &p->chip, p);
> +	if (ret) {
> +		dev_err(&pdev->dev, "unable to add gpio chip\n");
> +		return ret;
> +	}
> +
> +	dev_info(&pdev->dev, "elba spics registered\n");

Don't print trivial probe results, unless you print here something
useful. If you need it for debugging, keep it dev_dbg.

Best regards,
Krzysztof

On Thu, Mar 4, 2021 at 4:40 PM Brad Larson <brad@pensando.io> wrote:
>
> This GPIO driver is for the Pensando Elba SoC which
> provides control of four chip selects on two SPI busses.

I will try to avoid repeating otheris in their reviews, but my comments below.

...

> +config GPIO_ELBA_SPICS
> +       bool "Pensando Elba SPI chip-select"

Can't it be a module? Why?

> +       depends on ARCH_PENSANDO_ELBA_SOC
> +       help
> +         Say yes here to support the Pensndo Elba SoC SPI chip-select driver

Please give more explanation what it is and why users might need it,
and also tell users how the module will be named (if there is no
strong argument why it can't be a  module).

...

> +#include <linux/of.h>

It's not used here, but you missed mod_devicetable.h.

...

> +/*
> + * pin:             3            2        |       1            0
> + * bit:         7------6------5------4----|---3------2------1------0
> + *     cs1  cs1_ovr  cs0  cs0_ovr |  cs1  cs1_ovr  cs0  cs0_ovr
> + *                ssi1            |             ssi0
> + */
> +#define SPICS_PIN_SHIFT(pin)   (2 * (pin))
> +#define SPICS_MASK(pin)                (0x3 << SPICS_PIN_SHIFT(pin))

> +#define SPICS_SET(pin, val)    ((((val) << 1) | 0x1) << SPICS_PIN_SHIFT(pin))

Isn't it easier to define as ((value) << (2 * (pin) + 1) | BIT(2 * (pin)))

...

> +struct elba_spics_priv {
> +       void __iomem *base;
> +       spinlock_t lock;

> +       struct gpio_chip chip;

If you put it as a first member a container_of() becomes a no-op. OTOH
dunno if there is any such container_of() use in the code.

> +};

...

> +static int elba_spics_get_value(struct gpio_chip *chip, unsigned int pin)
> +{
> +       return -ENXIO;

Hmm... Is it really acceptable error code here?

> +}
...

> +static int elba_spics_direction_input(struct gpio_chip *chip, unsigned int pin)
> +{
> +       return -ENXIO;

Ditto.

> +}

...

> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       p->base = devm_ioremap_resource(&pdev->dev, res);

p->base = devm_platform_ioremap_resource(pdev, 0);

> +       if (IS_ERR(p->base)) {

> +               dev_err(&pdev->dev, "failed to remap I/O memory\n");

Duplicate noisy message.

> +               return PTR_ERR(p->base);
> +       }

> +       ret = devm_gpiochip_add_data(&pdev->dev, &p->chip, p);
> +       if (ret) {
> +               dev_err(&pdev->dev, "unable to add gpio chip\n");

> +               return ret;
> +       }
> +
> +       dev_info(&pdev->dev, "elba spics registered\n");
> +       return 0;

if (ret)
  dev_err(...);
return ret;

> +}

On Sun, Mar 7, 2021 at 11:21 AM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Thu, Mar 4, 2021 at 4:40 PM Brad Larson <brad@pensando.io> wrote:
> >
> > This GPIO driver is for the Pensando Elba SoC which
> > provides control of four chip selects on two SPI busses.
>
> > +config GPIO_ELBA_SPICS
> > +       bool "Pensando Elba SPI chip-select"
>
> Can't it be a module? Why?

All Elba SoC based platforms require this driver to be built-in to boot and
removing the module would result in a variety of exceptions/errors.

> > +       depends on ARCH_PENSANDO_ELBA_SOC
> > +       help
> > +         Say yes here to support the Pensndo Elba SoC SPI chip-select driver
>
> Please give more explanation what it is and why users might need it,
> and also tell users how the module will be named (if there is no
> strong argument why it can't be a  module).
>
Fixed the typo.

> > +#include <linux/of.h>
>
> It's not used here, but you missed mod_devicetable.h.

Removed <linux/of.h>.  There is no dependency on mod_devicetable.h.

> ...
>
> > +/*
> > + * pin:             3            2        |       1            0
> > + * bit:         7------6------5------4----|---3------2------1------0
> > + *     cs1  cs1_ovr  cs0  cs0_ovr |  cs1  cs1_ovr  cs0  cs0_ovr
> > + *                ssi1            |             ssi0
> > + */
> > +#define SPICS_PIN_SHIFT(pin)   (2 * (pin))
> > +#define SPICS_MASK(pin)                (0x3 << SPICS_PIN_SHIFT(pin))
>
> > +#define SPICS_SET(pin, val)    ((((val) << 1) | 0x1) << SPICS_PIN_SHIFT(pin))
>
> Isn't it easier to define as ((value) << (2 * (pin) + 1) | BIT(2 * (pin)))
>
> ...
>
> > +struct elba_spics_priv {
> > +       void __iomem *base;
> > +       spinlock_t lock;
>
> > +       struct gpio_chip chip;
>
> If you put it as a first member a container_of() becomes a no-op. OTOH
> dunno if there is any such container_of() use in the code.
>

There is no use of container_of()

> > +static int elba_spics_get_value(struct gpio_chip *chip, unsigned int pin)
> > +{
> > +       return -ENXIO;
>
> Hmm... Is it really acceptable error code here?
>
> > +static int elba_spics_direction_input(struct gpio_chip *chip, unsigned int pin)
> > +{
> > +       return -ENXIO;
>
> Ditto.
>
Changed both to -ENOTSUPP.

> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       p->base = devm_ioremap_resource(&pdev->dev, res);
>
> p->base = devm_platform_ioremap_resource(pdev, 0);

Implementation follows devm_ioremap_resource() example in lib/devres.c.

> > +       if (IS_ERR(p->base)) {
>
> > +               dev_err(&pdev->dev, "failed to remap I/O memory\n");
>
> Duplicate noisy message.
>
> > +               return PTR_ERR(p->base);
> > +       }
>
> > +       ret = devm_gpiochip_add_data(&pdev->dev, &p->chip, p);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "unable to add gpio chip\n");
>
> > +               return ret;
> > +       }
> > +
> > +       dev_info(&pdev->dev, "elba spics registered\n");
> > +       return 0;
>
> if (ret)
>   dev_err(...);
> return ret;

Cleaned this up in patchset v2.

On Mon, Mar 29, 2021 at 4:19 AM Brad Larson <brad@pensando.io> wrote:
> On Sun, Mar 7, 2021 at 11:21 AM Andy Shevchenko

> <andy.shevchenko@gmail.com> wrote:

> > On Thu, Mar 4, 2021 at 4:40 PM Brad Larson <brad@pensando.io> wrote:


...

> > > +config GPIO_ELBA_SPICS

> > > +       bool "Pensando Elba SPI chip-select"

> >

> > Can't it be a module? Why?

>

> All Elba SoC based platforms require this driver to be built-in to boot and

> removing the module would result in a variety of exceptions/errors.


Needs to be at least in the commit message.

> > > +       depends on ARCH_PENSANDO_ELBA_SOC

> > > +       help

> > > +         Say yes here to support the Pensndo Elba SoC SPI chip-select driver

> >

> > Please give more explanation what it is and why users might need it,

> > and also tell users how the module will be named (if there is no

> > strong argument why it can't be a  module).

> >

> Fixed the typo.


Yeah, according to the above, you better elaborate what this module is
and why people would need it.
Also can be a good hint to add
default ARCH_MY_COOL_PLATFORM

...

> > > +#include <linux/of.h>

> >

> > It's not used here, but you missed mod_devicetable.h.

>

> Removed <linux/of.h>.  There is no dependency on mod_devicetable.h.


What do you mean? You don't use data structures from that?
of_device_id or other ID structures are defined there. Your module
works without them?

...

> > > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

> > > +       p->base = devm_ioremap_resource(&pdev->dev, res);

> >

> > p->base = devm_platform_ioremap_resource(pdev, 0);

>

> Implementation follows devm_ioremap_resource() example in lib/devres.c.


So? How does this make it impossible to address my comment?

> > > +       if (IS_ERR(p->base)) {

> >

> > > +               dev_err(&pdev->dev, "failed to remap I/O memory\n");

> >

> > Duplicate noisy message.

> >

> > > +               return PTR_ERR(p->base);

> > > +       }


-- 
With Best Regards,
Andy Shevchenko

On Thu, Mar 4, 2021 at 12:29 AM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> Hi Brad,
>
> thanks for your patch!
>
> On Thu, Mar 4, 2021 at 4:42 AM Brad Larson <brad@pensando.io> wrote:
>
> > This GPIO driver is for the Pensando Elba SoC which
> > provides control of four chip selects on two SPI busses.
> >
> > Signed-off-by: Brad Larson <brad@pensando.io>
> (...)
>
> > +#include <linux/gpio.h>
>
> Use this in new drivers:
> #include <linux/gpio/driver.h>
>
> > + * pin:             3            2        |       1            0
> > + * bit:         7------6------5------4----|---3------2------1------0
> > + *     cs1  cs1_ovr  cs0  cs0_ovr |  cs1  cs1_ovr  cs0  cs0_ovr
> > + *                ssi1            |             ssi0
> > + */
> > +#define SPICS_PIN_SHIFT(pin)   (2 * (pin))
> > +#define SPICS_MASK(pin)                (0x3 << SPICS_PIN_SHIFT(pin))
> > +#define SPICS_SET(pin, val)    ((((val) << 1) | 0x1) << SPICS_PIN_SHIFT(pin))
>
> So 2 bits per GPIO line in one register? (Nice doc!)
>
> > +struct elba_spics_priv {
> > +       void __iomem *base;
> > +       spinlock_t lock;
> > +       struct gpio_chip chip;
> > +};
> > +
> > +static int elba_spics_get_value(struct gpio_chip *chip, unsigned int pin)
> > +{
> > +       return -ENXIO;
> > +}
>
> Write a comment that the chip only supports output mode,
> because it repurposes SPI CS pins as generic GPIO out,
> maybe at the top of the file?
>

I'll add a comment regarding gpio pin mode.  Yes output
only mode as SPI chip-selects.

> I suppose these systems also actually (ab)use the SPI cs
> for things that are not really SPI CS? Because otherwise
> this could just be part of the SPI driver (native chip select).
>
> > +static const struct of_device_id ebla_spics_of_match[] = {
> > +       { .compatible = "pensando,elba-spics" },
>
> Have you documented this?

Yes in Documentation/devicetree/bindings, I'll double check
the content for completeness.  The SPI CS isn't used for
something else, the integrated DesignWare IP doesn't
support 4 chip-selects on two spi busses.

>
> Other than that this is a nice and complete driver.
>
> Yours,
> Linus Walleij

Thanks for the review!

Hi Linus,

On Thu, Mar 4, 2021 at 12:29 AM Linus Walleij <linus.walleij@linaro.org> wrote:
> On Thu, Mar 4, 2021 at 4:42 AM Brad Larson <brad@pensando.io> wrote:
>
> > This GPIO driver is for the Pensando Elba SoC which
> > provides control of four chip selects on two SPI busses.
[...]
> > +#include <linux/gpio.h>
>
> Use this in new drivers:
> #include <linux/gpio/driver.h>

The updated patchset will use linux/gpio/driver.h

> > + * pin:             3            2        |       1            0
> > + * bit:         7------6------5------4----|---3------2------1------0
> > + *     cs1  cs1_ovr  cs0  cs0_ovr |  cs1  cs1_ovr  cs0  cs0_ovr
> > + *                ssi1            |             ssi0
> > + */
> > +#define SPICS_PIN_SHIFT(pin)   (2 * (pin))
> > +#define SPICS_MASK(pin)                (0x3 << SPICS_PIN_SHIFT(pin))
> > +#define SPICS_SET(pin, val)    ((((val) << 1) | 0x1) << SPICS_PIN_SHIFT(pin))
>
> So 2 bits per GPIO line in one register? (Nice doc!)
>
> > +struct elba_spics_priv {
> > +       void __iomem *base;
> > +       spinlock_t lock;
> > +       struct gpio_chip chip;
> > +};
> > +
> > +static int elba_spics_get_value(struct gpio_chip *chip, unsigned int pin)
> > +{
> > +       return -ENXIO;
> > +}
>
> Write a comment that the chip only supports output mode,
> because it repurposes SPI CS pins as generic GPIO out,
> maybe at the top of the file?

The top of the file will look like this in the updated patchset.

 * Pensando Elba ASIC SPI chip select driver.  The SoC supports output
 * direction only as it uses a generic GPIO pin for SPI CS.

> I suppose these systems also actually (ab)use the SPI cs
> for things that are not really SPI CS? Because otherwise
> this could just be part of the SPI driver (native chip select).

The SPI cs are not used for any other purpose, we needed four chip
selects and native DW supports two.

> > +static const struct of_device_id ebla_spics_of_match[] = {
> > +       { .compatible = "pensando,elba-spics" },
>
> Have you documented this?

Yes as part of patchset v2: [PATCH v2 11/13] dt-bindings: gpio: Add
Pensando Elba SoC support
which documents "pensando,elba-spics" in new file
bindings/gpio/pensando,elba-spics.yaml.

Regards,
Brad

Hi Linus,

On Thu, Mar 4, 2021 at 5:38 AM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Thu, Mar 4, 2021 at 10:10 AM Serge Semin <fancer.lancer@gmail.com> wrote:
> > On Thu, Mar 04, 2021 at 09:29:33AM +0100, Linus Walleij wrote:
>
> > > > + * pin:             3            2        |       1            0
> > > > + * bit:         7------6------5------4----|---3------2------1------0
> > > > + *             cs1  cs1_ovr  cs0  cs0_ovr |  cs1  cs1_ovr  cs0  cs0_ovr
> > > > + *                        ssi1            |             ssi0
> > > > + */
> > > > +#define SPICS_PIN_SHIFT(pin)   (2 * (pin))
> > > > +#define SPICS_MASK(pin)                (0x3 << SPICS_PIN_SHIFT(pin))
> > > > +#define SPICS_SET(pin, val)    ((((val) << 1) | 0x1) << SPICS_PIN_SHIFT(pin))
> > >
> >
> > > So 2 bits per GPIO line in one register? (Nice doc!)
> >
> > I suppose the first bit is the CS-pin-override flag. So when it's set
> > the output is directly driven by the second bit, otherwise the
> > corresponding DW APB SPI controller drives it. That's how the
> > multiplexing is implemented here.
>
> If these output lines are so tightly coupled to the SPI block
> and will not be used for any other GPO (general purpose output)
> I think it makes more sense to bundle the handling into the
> DW SPI driver, and activate it based on the Elba compatible
> string (if of_is_compatible(...)).
>
> I am a bit cautious because it has happened in the past that
> people repurpose CS lines who were originally for SPI CS
> to all kind of other purposes, such as a power-on LED and
> in that case it needs to be a separate GPIO driver. So the
> author needs to have a good idea about what is a realistic
> use case here.

The gpio pins being used for the Elba SoC SPI CS are dedicated to this
function.  Are you recommending that the code in
drivers/gpio/gpio-elba-spics.c be integrated into
drivers/spi/spi-dw-mmio.c?

Regards,
Brad

Hi Elliott,

On Thu, Mar 4, 2021 at 12:44 PM Elliott, Robert (Servers)
<elliott@hpe.com> wrote:
[...]
> > +config GPIO_ELBA_SPICS
> > +     bool "Pensando Elba SPI chip-select"
> > +     depends on ARCH_PENSANDO_ELBA_SOC
> > +     help
> > +       Say yes here to support the Pensndo Elba SoC SPI chip-select
> > driver
>
> Pensndo should be Pensando

Fixed the typo, thanks.

> > diff --git a/drivers/gpio/gpio-elba-spics.c b/drivers/gpio/gpio-elba-spics.c
> > + * Pensando Elba ASIC SPI chip select driver
> ...
> > +MODULE_LICENSE("GPL v2");
> > +MODULE_DESCRIPTION("Elba SPI chip-select driver");
>
> I think it's conventional to include the company name there, so
> start that with "Pensando Elba"

Ok, thanks.  BTW I deleted these lines as I should have used
builtin_platform_driver() and not a loadable module.

> Also, "SoC" and "ASIC" are sometimes included after Elba, but sometimes
> are not. Consistency might be helpful.
>
> > +static const struct of_device_id ebla_spics_of_match[] = {
> ...
> > +             .of_match_table = ebla_spics_of_match,
>
> ebla should be elba

Fixed the typo and using SoC which is more accurate.

Regards,
Brad

Hi Krzysztof,

On Fri, Mar 5, 2021 at 3:25 AM Krzysztof Kozlowski
<krzysztof.kozlowski@canonical.com> wrote:
>

> On 04/03/2021 04:41, Brad Larson wrote:

> > This GPIO driver is for the Pensando Elba SoC which

> > provides control of four chip selects on two SPI busses.

[...]
> > +     ret = devm_gpiochip_add_data(&pdev->dev, &p->chip, p);

> > +     if (ret) {

> > +             dev_err(&pdev->dev, "unable to add gpio chip\n");

> > +             return ret;

> > +     }

> > +

> > +     dev_info(&pdev->dev, "elba spics registered\n");

>

> Don't print trivial probe results, unless you print here something

> useful. If you need it for debugging, keep it dev_dbg.


Removed that extraneous logging

Regards,
Brad

Hi Geert,

On Fri, Mar 5, 2021 at 5:57 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Brad,
>
> On Thu, Mar 4, 2021 at 4:59 AM Brad Larson <brad@pensando.io> wrote:
> > This GPIO driver is for the Pensando Elba SoC which
> > provides control of four chip selects on two SPI busses.
[...]
> > +config GPIO_ELBA_SPICS
> > +       bool "Pensando Elba SPI chip-select"
> > +       depends on ARCH_PENSANDO_ELBA_SOC
>
> Any specific reason this can't be "... || COMPILE_TEST"?

Added COMPILE_TEST

Regards,
Brad

Hi Andy,

On Sun, Mar 7, 2021 at 11:21 AM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Thu, Mar 4, 2021 at 4:40 PM Brad Larson <brad@pensando.io> wrote:
> >
> > This GPIO driver is for the Pensando Elba SoC which
> > provides control of four chip selects on two SPI busses.
>
> I will try to avoid repeating otheris in their reviews, but my comments below.
>
> ...
>
> > +config GPIO_ELBA_SPICS
> > +       bool "Pensando Elba SPI chip-select"
>
> Can't it be a module? Why?
>
> > +       depends on ARCH_PENSANDO_ELBA_SOC
> > +       help
> > +         Say yes here to support the Pensndo Elba SoC SPI chip-select driver
>
> Please give more explanation what it is and why users might need it,
> and also tell users how the module will be named (if there is no
> strong argument why it can't be a  module).
>
> ...
>
> > +#include <linux/of.h>
>
> It's not used here, but you missed mod_devicetable.h.

Based on the feedback I realized this should not be a loadable module.
I should be using builtin_platform_driver(elba_spics_driver).
Currently I have this for gpio/Kconfig

config GPIO_ELBA_SPICS
        def_bool y
        depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

> > +/*
> > + * pin:             3            2        |       1            0
> > + * bit:         7------6------5------4----|---3------2------1------0
> > + *     cs1  cs1_ovr  cs0  cs0_ovr |  cs1  cs1_ovr  cs0  cs0_ovr
> > + *                ssi1            |             ssi0
> > + */
> > +#define SPICS_PIN_SHIFT(pin)   (2 * (pin))
> > +#define SPICS_MASK(pin)                (0x3 << SPICS_PIN_SHIFT(pin))
>
> > +#define SPICS_SET(pin, val)    ((((val) << 1) | 0x1) << SPICS_PIN_SHIFT(pin))
>
> Isn't it easier to define as ((value) << (2 * (pin) + 1) | BIT(2 * (pin)))

Both are functionally correct.  I don't have a preference, do you want
this change?

> > +struct elba_spics_priv {
> > +       void __iomem *base;
> > +       spinlock_t lock;
>
> > +       struct gpio_chip chip;
>
> If you put it as a first member a container_of() becomes a no-op. OTOH
> dunno if there is any such container_of() use in the code.

There is no use of container_of() for this structure

> > +static int elba_spics_get_value(struct gpio_chip *chip, unsigned int pin)
> > +{
> > +       return -ENXIO;
>
> Hmm... Is it really acceptable error code here?

No it's not, thanks.  Changed to -ENOTSUPP as gpio output direction
only is supported.

> > +static int elba_spics_direction_input(struct gpio_chip *chip, unsigned int pin)
> > +{
> > +       return -ENXIO;
>
> Ditto.

Changed to ENOTSUPP

> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       p->base = devm_ioremap_resource(&pdev->dev, res);
>
> p->base = devm_platform_ioremap_resource(pdev, 0);

Changed to single call to devm_platform_ioremap_resource(pdev, 0)

> > +       if (IS_ERR(p->base)) {
>
> > +               dev_err(&pdev->dev, "failed to remap I/O memory\n");
>
> Duplicate noisy message.

Removed extra log message

> > +               return PTR_ERR(p->base);
> > +       }
>
> > +       ret = devm_gpiochip_add_data(&pdev->dev, &p->chip, p);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "unable to add gpio chip\n");
>
> > +               return ret;
> > +       }
> > +
> > +       dev_info(&pdev->dev, "elba spics registered\n");
> > +       return 0;
>
> if (ret)
>   dev_err(...);
> return ret;

Yes, made this change and will include in v3 patchset

--- a/drivers/gpio/gpio-elba-spics.c
+++ b/drivers/gpio/gpio-elba-spics.c
@@ -91,13 +91,9 @@ static int elba_spics_probe(struct platform_device *pdev)
        ret = devm_gpiochip_add_data(&pdev->dev, &p->chip, p);
-       if (ret) {
+       if (ret)
                dev_err(&pdev->dev, "unable to add gpio chip\n");
-               return ret;
-       }
-
-       dev_info(&pdev->dev, "elba spics registered\n");
-       return 0;
+       return ret;

Regards,
Brad

Hi Andy,

On Mon, Mar 29, 2021 at 3:40 AM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Mon, Mar 29, 2021 at 4:19 AM Brad Larson <brad@pensando.io> wrote:
> > On Sun, Mar 7, 2021 at 11:21 AM Andy Shevchenko
> > <andy.shevchenko@gmail.com> wrote:
> > > On Thu, Mar 4, 2021 at 4:40 PM Brad Larson <brad@pensando.io> wrote:
>
> ...
>
> > > > +config GPIO_ELBA_SPICS
> > > > +       bool "Pensando Elba SPI chip-select"
> > >
> > > Can't it be a module? Why?
> >
> > All Elba SoC based platforms require this driver to be built-in to boot and
> > removing the module would result in a variety of exceptions/errors.
>
> Needs to be at least in the commit message.
>
>
>
> > > > +       depends on ARCH_PENSANDO_ELBA_SOC
> > > > +       help
> > > > +         Say yes here to support the Pensndo Elba SoC SPI chip-select driver
> > >
> > > Please give more explanation what it is and why users might need it,
> > > and also tell users how the module will be named (if there is no
> > > strong argument why it can't be a  module).
> > >
> > Fixed the typo.
>
> Yeah, according to the above, you better elaborate what this module is
> and why people would need it.
> Also can be a good hint to add
> default ARCH_MY_COOL_PLATFORM

Regarding the above module question and Kconfig definition, since I
first looked at this and reviewed the comments I realized I should be
using builtin.  The file gpio/Kconfig is currently this

config GPIO_ELBA_SPICS
        def_bool y
        depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

> ...
>
> > > > +#include <linux/of.h>
> > >
> > > It's not used here, but you missed mod_devicetable.h.
> >
> > Removed <linux/of.h>.  There is no dependency on mod_devicetable.h.
>
> What do you mean? You don't use data structures from that?
> of_device_id or other ID structures are defined there. Your module
> works without them?
>
I typed the wrong filename.  I do still have <linux/of.h>

> > > > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > > +       p->base = devm_ioremap_resource(&pdev->dev, res);
> > >
> > > p->base = devm_platform_ioremap_resource(pdev, 0);
> >
> > Implementation follows devm_ioremap_resource() example in lib/devres.c.
>
> So? How does this make it impossible to address my comment?

I was simply stating that I followed the recommended API per the
source code although I don't recall if I was looking at 4.14, 5.10 or
linux-next at the time.  Changed to using
devm_platform_ioremap_resource().

> > > > +       if (IS_ERR(p->base)) {
> > >
> > > > +               dev_err(&pdev->dev, "failed to remap I/O memory\n");
> > >
> > > Duplicate noisy message.
> > >
> > > > +               return PTR_ERR(p->base);
> > > > +       }

Yep, I've removed the extraneous log message.

Regards,
Brad

Hi Brad,

On Mon, Aug 23, 2021 at 3:14 AM Brad Larson <brad@pensando.io> wrote:
> On Mon, Mar 29, 2021 at 3:40 AM Andy Shevchenko
> <andy.shevchenko@gmail.com> wrote:
> >
> > On Mon, Mar 29, 2021 at 4:19 AM Brad Larson <brad@pensando.io> wrote:
> > > On Sun, Mar 7, 2021 at 11:21 AM Andy Shevchenko
> > > <andy.shevchenko@gmail.com> wrote:
> > > > On Thu, Mar 4, 2021 at 4:40 PM Brad Larson <brad@pensando.io> wrote:
> >
> > ...
> >
> > > > > +config GPIO_ELBA_SPICS
> > > > > +       bool "Pensando Elba SPI chip-select"
> > > >
> > > > Can't it be a module? Why?
> > >
> > > All Elba SoC based platforms require this driver to be built-in to boot and
> > > removing the module would result in a variety of exceptions/errors.
> >
> > Needs to be at least in the commit message.
> >
> > > > > +       depends on ARCH_PENSANDO_ELBA_SOC
> > > > > +       help
> > > > > +         Say yes here to support the Pensndo Elba SoC SPI chip-select driver

Pensando

> > > >
> > > > Please give more explanation what it is and why users might need it,
> > > > and also tell users how the module will be named (if there is no
> > > > strong argument why it can't be a  module).
> > > >
> > > Fixed the typo.
> >
> > Yeah, according to the above, you better elaborate what this module is
> > and why people would need it.
> > Also can be a good hint to add
> > default ARCH_MY_COOL_PLATFORM
>
> Regarding the above module question and Kconfig definition, since I
> first looked at this and reviewed the comments I realized I should be
> using builtin.  The file gpio/Kconfig is currently this
>
> config GPIO_ELBA_SPICS
>         def_bool y
>         depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

That means the driver will default to yes by merely enabling
COMPILE_TEST, which is a no-go.

    config GPIO_ELBA_SPICS
            bool "one-line summary"
            depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST
            default y if ARCH_PENSANDO_ELBA_SOC

Gr{oetje,eeting}s,

                        Geert

Hi Geert,

On Mon, Aug 23, 2021 at 12:50 AM Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
>
> Hi Brad,
>
> On Mon, Aug 23, 2021 at 3:14 AM Brad Larson <brad@pensando.io> wrote:
> > On Mon, Mar 29, 2021 at 3:40 AM Andy Shevchenko
[...]
> > Regarding the above module question and Kconfig definition, since I
> > first looked at this and reviewed the comments I realized I should be
> > using builtin.  The file gpio/Kconfig is currently this
> >
> > config GPIO_ELBA_SPICS
> >         def_bool y
> >         depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST
>
> That means the driver will default to yes by merely enabling
> COMPILE_TEST, which is a no-go.
>
>     config GPIO_ELBA_SPICS
>             bool "one-line summary"
>             depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST
>             default y if ARCH_PENSANDO_ELBA_SOC

Thanks Geert, changed to this

--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -241,8 +241,9 @@ config GPIO_EIC_SPRD
          Say yes here to support Spreadtrum EIC device.

 config GPIO_ELBA_SPICS
+       bool "Pensando Elba SoC SPI Chip Select as GPIO support"
+       depends on ARCH_PENSANDO_ELBA_SOC
        def_bool y
-       depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

Regards,
Brad

Hi Brad,

On Mon, Aug 23, 2021 at 6:31 PM Brad Larson <brad@pensando.io> wrote:
> On Mon, Aug 23, 2021 at 12:50 AM Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
> > On Mon, Aug 23, 2021 at 3:14 AM Brad Larson <brad@pensando.io> wrote:
> > > On Mon, Mar 29, 2021 at 3:40 AM Andy Shevchenko
> [...]
> > > Regarding the above module question and Kconfig definition, since I
> > > first looked at this and reviewed the comments I realized I should be
> > > using builtin.  The file gpio/Kconfig is currently this
> > >
> > > config GPIO_ELBA_SPICS
> > >         def_bool y
> > >         depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST
> >
> > That means the driver will default to yes by merely enabling
> > COMPILE_TEST, which is a no-go.
> >
> >     config GPIO_ELBA_SPICS
> >             bool "one-line summary"
> >             depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST
> >             default y if ARCH_PENSANDO_ELBA_SOC
>
> Thanks Geert, changed to this
>
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -241,8 +241,9 @@ config GPIO_EIC_SPRD
>           Say yes here to support Spreadtrum EIC device.
>
>  config GPIO_ELBA_SPICS
> +       bool "Pensando Elba SoC SPI Chip Select as GPIO support"
> +       depends on ARCH_PENSANDO_ELBA_SOC
>         def_bool y
> -       depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

So we're losing the COMPILE_TEST ability again?

Gr{oetje,eeting}s,

                        Geert

On Mon, Aug 23, 2021 at 3:06 AM Brad Larson <brad@pensando.io> wrote:

> The gpio pins being used for the Elba SoC SPI CS are dedicated to this
> function.  Are you recommending that the code in
> drivers/gpio/gpio-elba-spics.c be integrated into
> drivers/spi/spi-dw-mmio.c?

That makes most sense does it not?

Special purpose pins should be managed by that special purpose
hardware driver, DW SPI in this case.

The compatible string etc should be enough to determine that we
need some extra GPIO control here, possibly specify extra registers
for the SPI host etc.

The struct spi_master has a special callback .set_cs() and you
should make this behave special for your special hardware.
In the case of the DW driver it appears that even subdrivers can
pass a custom version of this call in struct dw_spi.

Yours,
Linus Walleij

On Mon, Aug 23, 2021 at 1:11 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>

> Hi Brad,

>

> On Mon, Aug 23, 2021 at 6:31 PM Brad Larson <brad@pensando.io> wrote:

> > On Mon, Aug 23, 2021 at 12:50 AM Geert Uytterhoeven

> > <geert@linux-m68k.org> wrote:

> > > On Mon, Aug 23, 2021 at 3:14 AM Brad Larson <brad@pensando.io> wrote:

> > > > On Mon, Mar 29, 2021 at 3:40 AM Andy Shevchenko

> > [...]

> > > > Regarding the above module question and Kconfig definition, since I

> > > > first looked at this and reviewed the comments I realized I should be

> > > > using builtin.  The file gpio/Kconfig is currently this

> > > >

> > > > config GPIO_ELBA_SPICS

> > > >         def_bool y

> > > >         depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

> > >

> > > That means the driver will default to yes by merely enabling

> > > COMPILE_TEST, which is a no-go.

> > >

> > >     config GPIO_ELBA_SPICS

> > >             bool "one-line summary"

> > >             depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

> > >             default y if ARCH_PENSANDO_ELBA_SOC

> >

> > Thanks Geert, changed to this

> >

> > --- a/drivers/gpio/Kconfig

> > +++ b/drivers/gpio/Kconfig

> > @@ -241,8 +241,9 @@ config GPIO_EIC_SPRD

> >           Say yes here to support Spreadtrum EIC device.

> >

> >  config GPIO_ELBA_SPICS

> > +       bool "Pensando Elba SoC SPI Chip Select as GPIO support"

> > +       depends on ARCH_PENSANDO_ELBA_SOC

> >         def_bool y

> > -       depends on ARCH_PENSANDO_ELBA_SOC || COMPILE_TEST

>

> So we're losing the COMPILE_TEST ability again?

>


Hi Geert,

The gpio-elba-spics.c driver is being deleted with the spi chip-select
control integrated into spi-dw-mmio.c.  The GPIO_ELBA_SPICS config
option goes away and fixes my breakage of COMPILE_TEST.

Best,
Brad