diff mbox series

[v1,3/3] spi: xilinx: Make num_chipselect 8-bit in the struct xspi_platform_data

Message ID 20240307154510.3795380-4-andriy.shevchenko@linux.intel.com
State New
Headers show
Series spi: xilinx: Massage xilinx_spi.h | expand

Commit Message

Andy Shevchenko March 7, 2024, 3:43 p.m. UTC
There is no use for whole 16-bit for the number of chip select pins.
Drop it to 8 bits and reshuffle the data structure layout to avoid
unnecessary paddings.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 include/linux/spi/xilinx_spi.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Comments

Michal Simek March 8, 2024, 8:20 a.m. UTC | #1
On 3/7/24 16:43, Andy Shevchenko wrote:
> There is no use for whole 16-bit for the number of chip select pins.
> Drop it to 8 bits and reshuffle the data structure layout to avoid
> unnecessary paddings.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>   include/linux/spi/xilinx_spi.h | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/spi/xilinx_spi.h b/include/linux/spi/xilinx_spi.h
> index 4ba8f53ce570..a638ba2a55bd 100644
> --- a/include/linux/spi/xilinx_spi.h
> +++ b/include/linux/spi/xilinx_spi.h
> @@ -8,18 +8,18 @@ struct spi_board_info;
>   
>   /**
>    * struct xspi_platform_data - Platform data of the Xilinx SPI driver
> + * @force_irq:		If set, forces QSPI transaction requirements.
>    * @num_chipselect:	Number of chip select by the IP.
>    * @bits_per_word:	Number of bits per word.
> - * @devices:		Devices to add when the driver is probed.
>    * @num_devices:	Number of devices in the devices array.
> - * @force_irq:		If set, forces QSPI transaction requirements.
> + * @devices:		Devices to add when the driver is probed.
>    */
>   struct xspi_platform_data {
> -	u16 num_chipselect;
> -	u8 bits_per_word;
> -	struct spi_board_info *devices;
> -	u8 num_devices;
>   	bool force_irq;
> +	u8 num_chipselect;
> +	u8 bits_per_word;
> +	u8 num_devices;

all above have 32bits. It means on 64bit cpu you have 32bit gap here.

> +	struct spi_board_info *devices;


It means this should be like this and then there is no gap between on 
32bit/64bit systems.

struct xspi_platform_data {
	struct spi_board_info *    devices;              /*     0     8 */
	bool                       force_irq;            /*     8     1 */
	u8                         num_chipselect;       /*     9     1 */
	u8                         bits_per_word;        /*    10     1 */
	u8                         num_devices;          /*    11     1 */

	/* size: 16, cachelines: 1, members: 5 */
	/* padding: 4 */
	/* last cacheline: 16 bytes */
};

Thanks,
Michal
Andy Shevchenko March 8, 2024, 1:31 p.m. UTC | #2
On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
> On 3/7/24 16:43, Andy Shevchenko wrote:

...

> >   struct xspi_platform_data {
> > -	u16 num_chipselect;
> > -	u8 bits_per_word;
> > -	struct spi_board_info *devices;
> > -	u8 num_devices;
> >   	bool force_irq;
> > +	u8 num_chipselect;
> > +	u8 bits_per_word;
> > +	u8 num_devices;
> 
> all above have 32bits. It means on 64bit cpu you have 32bit gap here.

> > +	struct spi_board_info *devices;

On all architectures? I mean do all 64-bit architecture ABIs _require_
the pointer to be aligned at 8-byte boundary? Even if so, the struct
itself can be aligned on 4-byte boundary.

> It means this should be like this and then there is no gap between on
> 32bit/64bit systems.
> 
> struct xspi_platform_data {
> 	struct spi_board_info *    devices;              /*     0     8 */
> 	bool                       force_irq;            /*     8     1 */
> 	u8                         num_chipselect;       /*     9     1 */
> 	u8                         bits_per_word;        /*    10     1 */
> 	u8                         num_devices;          /*    11     1 */
> 
> 	/* size: 16, cachelines: 1, members: 5 */
> 	/* padding: 4 */
> 	/* last cacheline: 16 bytes */
> };
Michal Simek March 8, 2024, 1:48 p.m. UTC | #3
On 3/8/24 14:31, Andy Shevchenko wrote:
> On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
>> On 3/7/24 16:43, Andy Shevchenko wrote:
> 
> ...
> 
>>>    struct xspi_platform_data {
>>> -	u16 num_chipselect;
>>> -	u8 bits_per_word;
>>> -	struct spi_board_info *devices;
>>> -	u8 num_devices;
>>>    	bool force_irq;
>>> +	u8 num_chipselect;
>>> +	u8 bits_per_word;
>>> +	u8 num_devices;
>>
>> all above have 32bits. It means on 64bit cpu you have 32bit gap here.
> 
>>> +	struct spi_board_info *devices;
> 
> On all architectures? I mean do all 64-bit architecture ABIs _require_
> the pointer to be aligned at 8-byte boundary? Even if so, the struct
> itself can be aligned on 4-byte boundary.

I am not able to tell if toolchain enforce 8byte alignment by default/by setup 
on all 64bit systems.
I am using pahole to check this which was recommended by Greg in past which 
reports gap in the middle.

thanks,
Michal
Andy Shevchenko March 8, 2024, 1:55 p.m. UTC | #4
On Fri, Mar 08, 2024 at 02:48:04PM +0100, Michal Simek wrote:
> On 3/8/24 14:31, Andy Shevchenko wrote:
> > On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
> > > On 3/7/24 16:43, Andy Shevchenko wrote:

...

> > > >    struct xspi_platform_data {
> > > > -	u16 num_chipselect;
> > > > -	u8 bits_per_word;
> > > > -	struct spi_board_info *devices;
> > > > -	u8 num_devices;
> > > >    	bool force_irq;
> > > > +	u8 num_chipselect;
> > > > +	u8 bits_per_word;
> > > > +	u8 num_devices;
> > > 
> > > all above have 32bits. It means on 64bit cpu you have 32bit gap here.
> > 
> > > > +	struct spi_board_info *devices;
> > 
> > On all architectures? I mean do all 64-bit architecture ABIs _require_
> > the pointer to be aligned at 8-byte boundary? Even if so, the struct
> > itself can be aligned on 4-byte boundary.
> 
> I am not able to tell if toolchain enforce 8byte alignment by default/by
> setup on all 64bit systems.
> I am using pahole to check this which was recommended by Greg in past which
> reports gap in the middle.

I see, thanks for explanation.

Yes, it's likely that in some cases it will be a gap on 64-bit platforms, but
after this patch no gap on 32-bit. Do you still want me to reshuffle that as
you suggested?
Michal Simek March 8, 2024, 2 p.m. UTC | #5
On 3/8/24 14:55, Andy Shevchenko wrote:
> On Fri, Mar 08, 2024 at 02:48:04PM +0100, Michal Simek wrote:
>> On 3/8/24 14:31, Andy Shevchenko wrote:
>>> On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
>>>> On 3/7/24 16:43, Andy Shevchenko wrote:
> 
> ...
> 
>>>>>     struct xspi_platform_data {
>>>>> -	u16 num_chipselect;
>>>>> -	u8 bits_per_word;
>>>>> -	struct spi_board_info *devices;
>>>>> -	u8 num_devices;
>>>>>     	bool force_irq;
>>>>> +	u8 num_chipselect;
>>>>> +	u8 bits_per_word;
>>>>> +	u8 num_devices;
>>>>
>>>> all above have 32bits. It means on 64bit cpu you have 32bit gap here.
>>>
>>>>> +	struct spi_board_info *devices;
>>>
>>> On all architectures? I mean do all 64-bit architecture ABIs _require_
>>> the pointer to be aligned at 8-byte boundary? Even if so, the struct
>>> itself can be aligned on 4-byte boundary.
>>
>> I am not able to tell if toolchain enforce 8byte alignment by default/by
>> setup on all 64bit systems.
>> I am using pahole to check this which was recommended by Greg in past which
>> reports gap in the middle.
> 
> I see, thanks for explanation.
> 
> Yes, it's likely that in some cases it will be a gap on 64-bit platforms, but
> after this patch no gap on 32-bit. Do you still want me to reshuffle that as
> you suggested?

Yes I would prefer to do that change when you are doing cleanup.

M
Andy Shevchenko March 8, 2024, 3:01 p.m. UTC | #6
On Fri, Mar 08, 2024 at 03:00:55PM +0100, Michal Simek wrote:
> On 3/8/24 14:55, Andy Shevchenko wrote:
> > On Fri, Mar 08, 2024 at 02:48:04PM +0100, Michal Simek wrote:
> > > On 3/8/24 14:31, Andy Shevchenko wrote:
> > > > On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
> > > > > On 3/7/24 16:43, Andy Shevchenko wrote:

...

> > > > > >     struct xspi_platform_data {
> > > > > > -	u16 num_chipselect;
> > > > > > -	u8 bits_per_word;
> > > > > > -	struct spi_board_info *devices;
> > > > > > -	u8 num_devices;
> > > > > >     	bool force_irq;
> > > > > > +	u8 num_chipselect;
> > > > > > +	u8 bits_per_word;
> > > > > > +	u8 num_devices;
> > > > > 
> > > > > all above have 32bits. It means on 64bit cpu you have 32bit gap here.
> > > > 
> > > > > > +	struct spi_board_info *devices;
> > > > 
> > > > On all architectures? I mean do all 64-bit architecture ABIs _require_
> > > > the pointer to be aligned at 8-byte boundary? Even if so, the struct
> > > > itself can be aligned on 4-byte boundary.
> > > 
> > > I am not able to tell if toolchain enforce 8byte alignment by default/by
> > > setup on all 64bit systems.
> > > I am using pahole to check this which was recommended by Greg in past which
> > > reports gap in the middle.
> > 
> > I see, thanks for explanation.
> > 
> > Yes, it's likely that in some cases it will be a gap on 64-bit platforms, but
> > after this patch no gap on 32-bit. Do you still want me to reshuffle that as
> > you suggested?
> 
> Yes I would prefer to do that change when you are doing cleanup.

Can you give your tag? Then I prepare a new version with addressed comments
against last patch.
Andy Shevchenko March 8, 2024, 3:01 p.m. UTC | #7
On Fri, Mar 08, 2024 at 05:01:20PM +0200, Andy Shevchenko wrote:
> On Fri, Mar 08, 2024 at 03:00:55PM +0100, Michal Simek wrote:
> > On 3/8/24 14:55, Andy Shevchenko wrote:
> > > On Fri, Mar 08, 2024 at 02:48:04PM +0100, Michal Simek wrote:
> > > > On 3/8/24 14:31, Andy Shevchenko wrote:
> > > > > On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
> > > > > > On 3/7/24 16:43, Andy Shevchenko wrote:

...

> > > > > > >     struct xspi_platform_data {
> > > > > > > -	u16 num_chipselect;
> > > > > > > -	u8 bits_per_word;
> > > > > > > -	struct spi_board_info *devices;
> > > > > > > -	u8 num_devices;
> > > > > > >     	bool force_irq;
> > > > > > > +	u8 num_chipselect;
> > > > > > > +	u8 bits_per_word;
> > > > > > > +	u8 num_devices;
> > > > > > 
> > > > > > all above have 32bits. It means on 64bit cpu you have 32bit gap here.
> > > > > 
> > > > > > > +	struct spi_board_info *devices;
> > > > > 
> > > > > On all architectures? I mean do all 64-bit architecture ABIs _require_
> > > > > the pointer to be aligned at 8-byte boundary? Even if so, the struct
> > > > > itself can be aligned on 4-byte boundary.
> > > > 
> > > > I am not able to tell if toolchain enforce 8byte alignment by default/by
> > > > setup on all 64bit systems.
> > > > I am using pahole to check this which was recommended by Greg in past which
> > > > reports gap in the middle.
> > > 
> > > I see, thanks for explanation.
> > > 
> > > Yes, it's likely that in some cases it will be a gap on 64-bit platforms, but
> > > after this patch no gap on 32-bit. Do you still want me to reshuffle that as
> > > you suggested?
> > 
> > Yes I would prefer to do that change when you are doing cleanup.
> 
> Can you give your tag?

I mean for the other patch, not this one :-)

> Then I prepare a new version with addressed comments
> against last patch.
diff mbox series

Patch

diff --git a/include/linux/spi/xilinx_spi.h b/include/linux/spi/xilinx_spi.h
index 4ba8f53ce570..a638ba2a55bd 100644
--- a/include/linux/spi/xilinx_spi.h
+++ b/include/linux/spi/xilinx_spi.h
@@ -8,18 +8,18 @@  struct spi_board_info;
 
 /**
  * struct xspi_platform_data - Platform data of the Xilinx SPI driver
+ * @force_irq:		If set, forces QSPI transaction requirements.
  * @num_chipselect:	Number of chip select by the IP.
  * @bits_per_word:	Number of bits per word.
- * @devices:		Devices to add when the driver is probed.
  * @num_devices:	Number of devices in the devices array.
- * @force_irq:		If set, forces QSPI transaction requirements.
+ * @devices:		Devices to add when the driver is probed.
  */
 struct xspi_platform_data {
-	u16 num_chipselect;
-	u8 bits_per_word;
-	struct spi_board_info *devices;
-	u8 num_devices;
 	bool force_irq;
+	u8 num_chipselect;
+	u8 bits_per_word;
+	u8 num_devices;
+	struct spi_board_info *devices;
 };
 
 #endif /* __LINUX_SPI_XILINX_SPI_H */