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[v2,0/4] Enable multiple MCAN on AM62x

Message ID 20230424195402.516-1-jm@ti.com
Headers show
Series Enable multiple MCAN on AM62x | expand

Message

Judith Mendez April 24, 2023, 7:53 p.m. UTC
On AM62x there is one MCAN in MAIN domain and two in MCU domain.
The MCANs in MCU domain were not enabled since there is no
hardware interrupt routed to A53 GIC interrupt controller.
Therefore A53 Linux cannot be interrupted by MCU MCANs.

This solution instantiates a hrtimer with 1 ms polling interval
for MCAN device when there is no hardware interrupt and there is
poll-interval property in DTB MCAN node. The hrtimer generates a
recurring software interrupt which allows to call the isr. The isr
will check if there is pending transaction by reading a register
and proceed normally if there is.

On AM62x, this series enables two MCU MCAN which will use the hrtimer
implementation. MCANs with hardware interrupt routed to A53 Linux
will continue to use the hardware interrupt as expected.

Timer polling method was tested on both classic CAN and CAN-FD
at 125 KBPS, 250 KBPS, 1 MBPS and 2.5 MBPS with 4 MBPS bitrate
switching.

Letency and CPU load benchmarks were tested on 3x MCAN on AM62x.
1 MBPS timer polling interval is the better timer polling interval
since it has comparable latency to hardware interrupt with the worse
case being 1ms + CAN frame propagation time and CPU load is not
substantial. Latency can be improved further with less than 1 ms
polling intervals, howerver it is at the cost of CPU usage since CPU
load increases at 0.5 ms.

Note that in terms of power, enabling MCU MCANs with timer-polling
implementation might have negative impact since we will have to wake
up every 1 ms whether there are CAN packets pending in the RX FIFO or
not. This might prevent the CPU from entering into deeper idle states
for extended periods of time.

This patch series depends on 'Enable CAN PHY transceiver driver':
https://lore.kernel.org/lkml/775ec9ce-7668-429c-a977-6c8995968d6e@app.fastmail.com/T/

Previously sent an RFC:
https://lore.kernel.org/linux-can/52a37e51-4143-9017-42ee-8d17c67028e3@ti.com/T/#t

Changes since v1:
- Add poll-interval property to bindings and MCAN DTB node
- Add functionality to check for 'poll-interval' property in MCAN node 
- Bindings: add an example using poll-interval
- Add 'polling' flag in driver to check if device is using polling method
- Check for both timer polling and hardware interrupt case, default to
hardware interrupt method
- Change ns_to_ktime() to ms_to_ktime()

Judith Mendez (4):
  can: m_can: Add hrtimer to generate software interrupt
  dt-bindings: net: can: Add poll-interval for MCAN
  arm64: dts: ti: Add AM62x MCAN MAIN domain transceiver overlay
  arm64: dts: ti: Enable MCU MCANs for AM62x

 .../bindings/net/can/bosch,m_can.yaml         | 26 ++++++++-
 arch/arm64/boot/dts/ti/Makefile               |  2 +
 arch/arm64/boot/dts/ti/k3-am62-mcu.dtsi       | 24 ++++++++
 .../boot/dts/ti/k3-am625-sk-mcan-main.dtso    | 35 ++++++++++++
 .../boot/dts/ti/k3-am625-sk-mcan-mcu.dtso     | 57 +++++++++++++++++++
 drivers/net/can/m_can/m_can.c                 | 30 ++++++++--
 drivers/net/can/m_can/m_can.h                 |  5 ++
 drivers/net/can/m_can/m_can_platform.c        | 31 +++++++++-
 8 files changed, 200 insertions(+), 10 deletions(-)
 create mode 100644 arch/arm64/boot/dts/ti/k3-am625-sk-mcan-main.dtso
 create mode 100644 arch/arm64/boot/dts/ti/k3-am625-sk-mcan-mcu.dtso

Comments

Marc Kleine-Budde April 24, 2023, 8:14 p.m. UTC | #1
On 24.04.2023 14:53:59, Judith Mendez wrote:
> Add an hrtimer to MCAN class device. Each MCAN will have its own
> hrtimer instantiated if there is no hardware interrupt found and
> poll-interval property is defined in device tree M_CAN node.
> 
> The hrtimer will generate a software interrupt every 1 ms. In
> hrtimer callback, we check if there is a transaction pending by
> reading a register, then process by calling the isr if there is.
> 
> Signed-off-by: Judith Mendez <jm@ti.com>
> ---
> Changelog:
> v2:
> 	1. Add poll-interval to MCAN class device to check if poll-interval propery is
> 	present in MCAN node, this enables timer polling method.
> 	2. Add 'polling' flag to MCAN class device to check if a device is using timer
> 	polling method
> 	3. Check if both timer polling and hardware interrupt are enabled for a MCAN
> 	device, default to hardware interrupt mode if both are enabled.
> 	4. Changed ms_to_ktime() to ns_to_ktime()
> 	5. Removed newlines, tabs, and restructure if/else section.
> 
>  drivers/net/can/m_can/m_can.c          | 30 ++++++++++++++++++++-----
>  drivers/net/can/m_can/m_can.h          |  5 +++++
>  drivers/net/can/m_can/m_can_platform.c | 31 ++++++++++++++++++++++++--
>  3 files changed, 59 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index a5003435802b..33e094f88da1 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -23,6 +23,7 @@
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/hrtimer.h>

keep the list of includes sorted

>  
>  #include "m_can.h"
>  
> @@ -1587,6 +1588,11 @@ static int m_can_close(struct net_device *dev)
>  	if (!cdev->is_peripheral)
>  		napi_disable(&cdev->napi);
>  
> +	if (cdev->polling) {
> +		dev_dbg(cdev->dev, "Disabling the hrtimer\n");
> +		hrtimer_cancel(&cdev->hrtimer);
> +	}
> +
>  	m_can_stop(dev);
>  	m_can_clk_stop(cdev);
>  	free_irq(dev->irq, dev);
> @@ -1793,6 +1799,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
>  	return NETDEV_TX_OK;
>  }
>  
> +enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
> +{
> +	struct m_can_classdev *cdev =
> +		container_of(timer, struct m_can_classdev, hrtimer);
> +
> +	m_can_isr(0, cdev->net);
> +
> +	hrtimer_forward_now(timer, ms_to_ktime(1));

Please create a define for this

> +
> +	return HRTIMER_RESTART;
> +}
> +
>  static int m_can_open(struct net_device *dev)
>  {
>  	struct m_can_classdev *cdev = netdev_priv(dev);
> @@ -1827,13 +1845,15 @@ static int m_can_open(struct net_device *dev)
>  		}
>  
>  		INIT_WORK(&cdev->tx_work, m_can_tx_work_queue);
> -
>  		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
> -					   IRQF_ONESHOT,
> -					   dev->name, dev);
> -	} else {
> -		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
> +					   IRQF_ONESHOT, dev->name, dev);
> +	} else if (!cdev->polling) {
> +			err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>  				  dev);

No need to change the indention

> +	} else {
> +		dev_dbg(cdev->dev, "Start hrtimer\n");
> +		cdev->hrtimer.function = &hrtimer_callback;
> +		hrtimer_start(&cdev->hrtimer, ms_to_ktime(cdev->poll_interval), HRTIMER_MODE_REL_PINNED);
>  	}
>  
>  	if (err < 0) {
> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
> index a839dc71dc9b..1ba87eb23f8e 100644
> --- a/drivers/net/can/m_can/m_can.h
> +++ b/drivers/net/can/m_can/m_can.h
> @@ -28,6 +28,7 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
> +#include <linux/hrtimer.h>

keep the list of includes sorted

>  
>  /* m_can lec values */
>  enum m_can_lec_type {
> @@ -93,6 +94,10 @@ struct m_can_classdev {
>  	int is_peripheral;
>  
>  	struct mram_cfg mcfg[MRAM_CFG_NUM];
> +
> +	struct hrtimer hrtimer;
> +	u32 poll_interval;
> +	u8 polling;

bool

>  };
>  
>  struct m_can_classdev *m_can_class_allocate_dev(struct device *dev, int sizeof_priv);
> diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
> index 9c1dcf838006..e899c04edc01 100644
> --- a/drivers/net/can/m_can/m_can_platform.c
> +++ b/drivers/net/can/m_can/m_can_platform.c
> @@ -7,6 +7,7 @@
>  
>  #include <linux/phy/phy.h>
>  #include <linux/platform_device.h>
> +#include <linux/hrtimer.h>
>  
>  #include "m_can.h"
>  
> @@ -97,11 +98,37 @@ static int m_can_plat_probe(struct platform_device *pdev)
>  
>  	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
>  	irq = platform_get_irq_byname(pdev, "int0");

use platform_get_irq_byname_optional(), it doesn't print an error
message.

> -	if (IS_ERR(addr) || irq < 0) {
> -		ret = -EINVAL;
> +	if (irq == -EPROBE_DEFER) {
> +		ret = -EPROBE_DEFER;
>  		goto probe_fail;
>  	}
>  
> +	if (IS_ERR(addr)) {
> +		ret = PTR_ERR(addr);
> +		goto probe_fail;
> +	}

please move the error check for "addr" directly after the "addr = "
assignment.

> +
> +	mcan_class->polling = 0;

No need to init as "0"

> +	if (device_property_present(mcan_class->dev, "poll-interval")) {
> +		mcan_class->polling = 1;
> +	}

No need for the { } here.

> +
> +	if (!mcan_class->polling && irq < 0) {
> +		ret = -ENODATA;
-ENXIO
> +		dev_dbg(mcan_class->dev, "Polling not enabled\n");

print a proper error message using dev_err_probe("IRQ %s not found and
polling not activated\n")

> +		goto probe_fail;
> +	}
> +
> +	if (mcan_class->polling && irq > 0) {
> +		mcan_class->polling = 0;
> +		dev_dbg(mcan_class->dev, "Polling not enabled, hardware interrupt exists\n");
> +	}
> +
> +	if (mcan_class->polling && irq < 0) {
> +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
> +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
> +	}

combine both if (mcan_class->polling) into one.

> +
>  	/* message ram could be shared */
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>  	if (!res) {
> -- 
> 2.17.1
> 
> 

Marc
Nishanth Menon April 25, 2023, 12:47 p.m. UTC | #2
On 14:54-20230424, Judith Mendez wrote:
> Add an overlay for main domain MCAN on AM62x SK. The AM62x
> SK board does not have on-board CAN transceiver so instead
> of changing the DTB permanently, add an overlay to enable
> MAIN domain MCAN and support for 1 CAN transceiver.
> 
> Signed-off-by: Judith Mendez <jm@ti.com>
> ---
>  arch/arm64/boot/dts/ti/Makefile               |  2 ++
>  .../boot/dts/ti/k3-am625-sk-mcan-main.dtso    | 35 +++++++++++++++++++
>  2 files changed, 37 insertions(+)
>  create mode 100644 arch/arm64/boot/dts/ti/k3-am625-sk-mcan-main.dtso
> 

Just a headsup - for a formal patch, for the overlay, please ensure we
provide link to the specific board. I dont want to end up with 1000s
of overlay files, each enabling one specific peripheral instance of a
small subgroup of peripheral instance. Overlays should be describing a
real platform with product link.

> diff --git a/arch/arm64/boot/dts/ti/Makefile b/arch/arm64/boot/dts/ti/Makefile
> index c83c9d772b81..abe15e76b614 100644
> --- a/arch/arm64/boot/dts/ti/Makefile
> +++ b/arch/arm64/boot/dts/ti/Makefile
> @@ -9,8 +9,10 @@
>  # alphabetically.
>  
>  # Boards with AM62x SoC
> +k3-am625-sk-mcan-dtbs := k3-am625-sk.dtb k3-am625-sk-mcan-main.dtbo
>  dtb-$(CONFIG_ARCH_K3) += k3-am625-beagleplay.dtb
>  dtb-$(CONFIG_ARCH_K3) += k3-am625-sk.dtb
> +dtb-$(CONFIG_ARCH_K3) += k3-am625-sk-mcan.dtb
>  dtb-$(CONFIG_ARCH_K3) += k3-am62-lp-sk.dtb
>  
>  # Boards with AM62Ax SoC
> diff --git a/arch/arm64/boot/dts/ti/k3-am625-sk-mcan-main.dtso b/arch/arm64/boot/dts/ti/k3-am625-sk-mcan-main.dtso
> new file mode 100644
> index 000000000000..0a7b2f394f87
> --- /dev/null
> +++ b/arch/arm64/boot/dts/ti/k3-am625-sk-mcan-main.dtso
> @@ -0,0 +1,35 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/**
> + * DT overlay for MCAN transceiver in main domain on AM625 SK
> + *
> + * Copyright (C) 2022 Texas Instruments Incorporated - https://www.ti.com/
> + */
> +
> +/dts-v1/;
> +/plugin/;
> +
> +#include "k3-pinctrl.h"
> +
> +&{/} {
> +	transceiver1: can-phy0 {
> +		compatible = "ti,tcan1042";
> +		#phy-cells = <0>;
> +		max-bitrate = <5000000>;
> +	};
> +};
> +
> +&main_pmx0 {
> +	main_mcan0_pins_default: main-mcan0-pins-default {
> +		pinctrl-single,pins = <
> +			AM62X_IOPAD(0x1dc, PIN_INPUT, 0) /* (E15) MCAN0_RX */
> +			AM62X_IOPAD(0x1d8, PIN_OUTPUT, 0) /* (C15) MCAN0_TX */
> +		>;
> +	};
> +};
> +
> +&main_mcan0 {
> +	status = "okay";
> +	pinctrl-names = "default";
> +	pinctrl-0 = <&main_mcan0_pins_default>;
> +	phys = <&transceiver1>;
> +};
> -- 
> 2.17.1
>
Judith Mendez April 26, 2023, 4:11 p.m. UTC | #3
Hello Marc,

On 4/24/2023 3:14 PM, Marc Kleine-Budde wrote:
> On 24.04.2023 14:53:59, Judith Mendez wrote:
>> Add an hrtimer to MCAN class device. Each MCAN will have its own
>> hrtimer instantiated if there is no hardware interrupt found and
>> poll-interval property is defined in device tree M_CAN node.
>>
>> The hrtimer will generate a software interrupt every 1 ms. In
>> hrtimer callback, we check if there is a transaction pending by
>> reading a register, then process by calling the isr if there is.
>>
>> Signed-off-by: Judith Mendez <jm@ti.com>
>> ---
>> Changelog:
>> v2:
>> 	1. Add poll-interval to MCAN class device to check if poll-interval propery is
>> 	present in MCAN node, this enables timer polling method.
>> 	2. Add 'polling' flag to MCAN class device to check if a device is using timer
>> 	polling method
>> 	3. Check if both timer polling and hardware interrupt are enabled for a MCAN
>> 	device, default to hardware interrupt mode if both are enabled.
>> 	4. Changed ms_to_ktime() to ns_to_ktime()
>> 	5. Removed newlines, tabs, and restructure if/else section.
>>
>>   drivers/net/can/m_can/m_can.c          | 30 ++++++++++++++++++++-----
>>   drivers/net/can/m_can/m_can.h          |  5 +++++
>>   drivers/net/can/m_can/m_can_platform.c | 31 ++++++++++++++++++++++++--
>>   3 files changed, 59 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
>> index a5003435802b..33e094f88da1 100644
>> --- a/drivers/net/can/m_can/m_can.c
>> +++ b/drivers/net/can/m_can/m_can.c
>> @@ -23,6 +23,7 @@
>>   #include <linux/pinctrl/consumer.h>
>>   #include <linux/platform_device.h>
>>   #include <linux/pm_runtime.h>
>> +#include <linux/hrtimer.h>
> 
> keep the list of includes sorted
> 
Will do.
>>   
>>   #include "m_can.h"
>>   
>> @@ -1587,6 +1588,11 @@ static int m_can_close(struct net_device *dev)
>>   	if (!cdev->is_peripheral)
>>   		napi_disable(&cdev->napi);
>>   
>> +	if (cdev->polling) {
>> +		dev_dbg(cdev->dev, "Disabling the hrtimer\n");
>> +		hrtimer_cancel(&cdev->hrtimer);
>> +	}
>> +
>>   	m_can_stop(dev);
>>   	m_can_clk_stop(cdev);
>>   	free_irq(dev->irq, dev);
>> @@ -1793,6 +1799,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
>>   	return NETDEV_TX_OK;
>>   }
>>   
>> +enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
>> +{
>> +	struct m_can_classdev *cdev =
>> +		container_of(timer, struct m_can_classdev, hrtimer);
>> +
>> +	m_can_isr(0, cdev->net);
>> +
>> +	hrtimer_forward_now(timer, ms_to_ktime(1));
> 
> Please create a define for this
> 
Thanks, will create a define for the 1 ms polling interval.

>> +
>> +	return HRTIMER_RESTART;
>> +}
>> +
>>   static int m_can_open(struct net_device *dev)
>>   {
>>   	struct m_can_classdev *cdev = netdev_priv(dev);
>> @@ -1827,13 +1845,15 @@ static int m_can_open(struct net_device *dev)
>>   		}
>>   
>>   		INIT_WORK(&cdev->tx_work, m_can_tx_work_queue);
>> -
>>   		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
>> -					   IRQF_ONESHOT,
>> -					   dev->name, dev);
>> -	} else {
>> -		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>> +					   IRQF_ONESHOT, dev->name, dev);
>> +	} else if (!cdev->polling) {
>> +			err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>>   				  dev);
> 
> No need to change the indention
> 
Will fix.

>> +	} else {
>> +		dev_dbg(cdev->dev, "Start hrtimer\n");
>> +		cdev->hrtimer.function = &hrtimer_callback;
>> +		hrtimer_start(&cdev->hrtimer, ms_to_ktime(cdev->poll_interval), HRTIMER_MODE_REL_PINNED);
>>   	}
>>   
>>   	if (err < 0) {
>> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
>> index a839dc71dc9b..1ba87eb23f8e 100644
>> --- a/drivers/net/can/m_can/m_can.h
>> +++ b/drivers/net/can/m_can/m_can.h
>> @@ -28,6 +28,7 @@
>>   #include <linux/pm_runtime.h>
>>   #include <linux/slab.h>
>>   #include <linux/uaccess.h>
>> +#include <linux/hrtimer.h>
> 
> keep the list of includes sorted
> 
>>   
>>   /* m_can lec values */
>>   enum m_can_lec_type {
>> @@ -93,6 +94,10 @@ struct m_can_classdev {
>>   	int is_peripheral;
>>   
>>   	struct mram_cfg mcfg[MRAM_CFG_NUM];
>> +
>> +	struct hrtimer hrtimer;
>> +	u32 poll_interval;
>> +	u8 polling;
> 
> bool
> 
Will use bool instead.
>>   };
>>   
>>   struct m_can_classdev *m_can_class_allocate_dev(struct device *dev, int sizeof_priv);
>> diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
>> index 9c1dcf838006..e899c04edc01 100644
>> --- a/drivers/net/can/m_can/m_can_platform.c
>> +++ b/drivers/net/can/m_can/m_can_platform.c
>> @@ -7,6 +7,7 @@
>>   
>>   #include <linux/phy/phy.h>
>>   #include <linux/platform_device.h>
>> +#include <linux/hrtimer.h>
>>   
>>   #include "m_can.h"
>>   
>> @@ -97,11 +98,37 @@ static int m_can_plat_probe(struct platform_device *pdev)
>>   
>>   	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
>>   	irq = platform_get_irq_byname(pdev, "int0");
> 
> use platform_get_irq_byname_optional(), it doesn't print an error
> message.
> 
Thanks.

>> -	if (IS_ERR(addr) || irq < 0) {
>> -		ret = -EINVAL;
>> +	if (irq == -EPROBE_DEFER) {
>> +		ret = -EPROBE_DEFER;
>>   		goto probe_fail;
>>   	}
>>   
>> +	if (IS_ERR(addr)) {
>> +		ret = PTR_ERR(addr);
>> +		goto probe_fail;
>> +	}
> 
> please move the error check for "addr" directly after the "addr = "
> assignment.
> 
Will do.
>> +
>> +	mcan_class->polling = 0;
> 
> No need to init as "0"
> 

Awsome thanks.
>> +	if (device_property_present(mcan_class->dev, "poll-interval")) {
>> +		mcan_class->polling = 1;
>> +	}
> 
> No need for the { } here.
> 
>> +
>> +	if (!mcan_class->polling && irq < 0) {
>> +		ret = -ENODATA;
> -ENXIO
>> +		dev_dbg(mcan_class->dev, "Polling not enabled\n");
> 
> print a proper error message using dev_err_probe("IRQ %s not found and
> polling not activated\n")
> 
Why %s when MCAN requests 1 IRQ which is "int0"? If we want to print 
"int0", should it be hardcoded into the print error message?

>> +		goto probe_fail;
>> +	}
>> +
>> +	if (mcan_class->polling && irq > 0) {
>> +		mcan_class->polling = 0;
>> +		dev_dbg(mcan_class->dev, "Polling not enabled, hardware interrupt exists\n");
>> +	}
>> +
>> +	if (mcan_class->polling && irq < 0) {
>> +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
>> +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
>> +	}
> 
> combine both if (mcan_class->polling) into one.
> 
Will do.
>> +
>>   	/* message ram could be shared */
>>   	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>>   	if (!res) {
>> -- 
>> 2.17.1
>>
>>

regards,
Judith
Marc Kleine-Budde April 26, 2023, 5:47 p.m. UTC | #4
On 26.04.2023 11:11:12, Mendez, Judith wrote:
[...]
> > print a proper error message using dev_err_probe("IRQ %s not found and
> > polling not activated\n")
> > 
> Why %s when MCAN requests 1 IRQ which is "int0"? If we want to print "int0",
> should it be hardcoded into the print error message?

I think I copied the error message from platform_get_irq_byname() and
extended it. Of course it makes sense to hardcode the IRQ name.

Marc