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

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Date:   Wed, 22 Apr 2020 12:09:54 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
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>, Haibo 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: [RESEND 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>
Tested-by: Haibo Chen <haibo.chen@....com>
Reviewed-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 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 5255550b7c34..b27d0f6c18c9 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -380,6 +380,8 @@ 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 bdc35753ef7c..77a2aada106d 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