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SubjectRE: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for platform devices
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> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@linaro.org>
> Sent: 2020年4月1日 2:39
> To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Rafael J . Wysocki
> <rafael@kernel.org>; linux-kernel@vger.kernel.org
> Cc: Arnd Bergmann <arnd@arndb.de>; Christoph Hellwig <hch@lst.de>;
> Russell King <linux@armlinux.org.uk>; Linus Walleij
> <linus.walleij@linaro.org>; Robin Murphy <robin.murphy@arm.com>; Vinod
> Koul <vkoul@kernel.org>; BOUGH CHEN <haibo.chen@nxp.com>; Ludovic
> Barre <ludovic.barre@st.com>; linux-arm-kernel@lists.infradead.org;
> dmaengine@vger.kernel.org; Ulf Hansson <ulf.hansson@linaro.org>;
> stable@vger.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@lst.de>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.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@nxp.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

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