linux-kernel - RE: [PATCH v2 1/2] driver core: platform: Initialize dma

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Date:   Wed, 1 Apr 2020 04:06:58 +0000
From:   BOUGH CHEN <haibo.chen@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Arnd Bergmann <arnd@...db.de>, Christoph Hellwig <hch@....de>,
        Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Robin Murphy <robin.murphy@....com>,
        Vinod Koul <vkoul@...nel.org>,
        Ludovic Barre <ludovic.barre@...com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for
 platform devices


> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@...aro.org>
> Sent: 2020年4月1日 2:39
> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Rafael J . Wysocki
> <rafael@...nel.org>; linux-kernel@...r.kernel.org
> Cc: Arnd Bergmann <arnd@...db.de>; Christoph Hellwig <hch@....de>;
> Russell King <linux@...linux.org.uk>; Linus Walleij
> <linus.walleij@...aro.org>; Robin Murphy <robin.murphy@....com>; Vinod
> Koul <vkoul@...nel.org>; BOUGH CHEN <haibo.chen@....com>; Ludovic
> Barre <ludovic.barre@...com>; linux-arm-kernel@...ts.infradead.org;
> dmaengine@...r.kernel.org; Ulf Hansson <ulf.hansson@...aro.org>;
> stable@...r.kernel.org
> 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@....de>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> 

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@....com>

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