RE: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for platform devices

[BOUGH CHEN]

> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Sent: 2020年4月1日 2:39
> To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Rafael J . Wysocki
> <rafael@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx
> Cc: Arnd Bergmann <arnd@xxxxxxxx>; Christoph Hellwig <hch@xxxxxx>;
> Russell King <linux@xxxxxxxxxxxxxxx>; Linus Walleij
> <linus.walleij@xxxxxxxxxx>; Robin Murphy <robin.murphy@xxxxxxx>; Vinod
> Koul <vkoul@xxxxxxxxxx>; BOUGH CHEN <haibo.chen@xxxxxxx>; Ludovic
> Barre <ludovic.barre@xxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> dmaengine@xxxxxxxxxxxxxxx; Ulf Hansson <ulf.hansson@xxxxxxxxxx>;
> stable@xxxxxxxxxxxxxxx
> Subject: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for
> platform devices
> 
> It's currently the platform driver's responsibility to initialize the pointer,
> dma_parms, for its corresponding struct device. The benefit with this
> approach allows us to avoid the initialization and to not waste memory for
> the struct device_dma_parameters, as this can be decided on a case by case
> basis.
> 
> However, it has turned out that this approach is not very practical.  Not
> only does it lead to open coding, but also to real errors. In principle callers of
> dma_set_max_seg_size() doesn't check the error code, but just assumes it
> succeeds.
> 
> For these reasons, let's do the initialization from the common platform bus
> at the device registration point. This also follows the way the PCI devices are
> being managed, see pci_device_add().
> 
> Suggested-by: Christoph Hellwig <hch@xxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> 

Hi Ulf,

I test both on our local 5.4.24 branch and the latest Linux-next, both works fine.

Tested-by: Haibo Chen <haibo.chen@xxxxxxx>

Best Regards
Haibo Chen

> ---
> 
> Changes in v2:
> 	- Move initialization to setup_pdev_dma_masks(). This means the
> 	initialization is done also in the OF path.
> 
> ---
>  drivers/base/platform.c         | 2 ++
>  include/linux/platform_device.h | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c index
> b5ce7b085795..c81b68d5d66d 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -361,6 +361,8 @@ struct platform_object {
>   */
>  static void setup_pdev_dma_masks(struct platform_device *pdev)  {
> +	pdev->dev.dma_parms = &pdev->dma_parms;
> +
>  	if (!pdev->dev.coherent_dma_mask)
>  		pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
>  	if (!pdev->dev.dma_mask) {
> diff --git a/include/linux/platform_device.h
> b/include/linux/platform_device.h index 041bfa412aa0..81900b3cbe37
> 100644
> --- a/include/linux/platform_device.h
> +++ b/include/linux/platform_device.h
> @@ -25,6 +25,7 @@ struct platform_device {
>  	bool		id_auto;
>  	struct device	dev;
>  	u64		platform_dma_mask;
> +	struct device_dma_parameters dma_parms;
>  	u32		num_resources;
>  	struct resource	*resource;
> 
> --
> 2.20.1