linux-kernel - [PATCH 5.6 077/118] amba: Initialize dma

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Date:   Wed, 13 May 2020 11:44:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Russell King <linux@...linux.org.uk>,
        Haibo Chen <haibo.chen@....com>, Arnd Bergmann <arnd@...db.de>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 5.6 077/118] amba: Initialize dma_parms for amba devices

From: Ulf Hansson <ulf.hansson@...aro.org>

commit f458488425f1cc9a396aa1d09bb00c48783936da upstream.

It's currently the amba 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 amba 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: Russell King <linux@...linux.org.uk>
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>
Reviewed-by: Christoph Hellwig <hch@....de>
Link: https://lore.kernel.org/r/20200422101013.31267-1-ulf.hansson@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/amba/bus.c       |    1 +
 include/linux/amba/bus.h |    1 +
 2 files changed, 2 insertions(+)

--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -645,6 +645,7 @@ static void amba_device_initialize(struc
 	dev->dev.release = amba_device_release;
 	dev->dev.bus = &amba_bustype;
 	dev->dev.dma_mask = &dev->dev.coherent_dma_mask;
+	dev->dev.dma_parms = &dev->dma_parms;
 	dev->res.name = dev_name(&dev->dev);
 }
 
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h
@@ -65,6 +65,7 @@ struct amba_device {
 	struct device		dev;
 	struct resource		res;
 	struct clk		*pclk;
+	struct device_dma_parameters dma_parms;
 	unsigned int		periphid;
 	unsigned int		cid;
 	struct amba_cs_uci_id	uci;