of: restrict DMA configuration (72328883) · Commits · 戴 / test

Moving DMA configuration to happen later at driver probe time had the unnoticed side-effect that we now perform DMA configuration for *every* device represented in DT, rather than only those explicitly created by the of_platform and PCI code. As Christoph points out, this is not really the best thing to do. Whilst there may well be other DMA-capable buses that can benefit from having their children automatically configured after the bridge has probed, there are also plenty of others like USB, MDIO, etc. that definitely do not support DMA and should not be indiscriminately processed. The good news is that in most cases the DT "dma-ranges" property serves as an appropriate indicator - per a strict interpretation of the spec, anything lacking a "dma-ranges" property should be considered not to have a mapping of DMA address space from its children to its parent, thus anything for which of_dma_get_range() does not succeed does not need DMA configuration. Certain bus types have a general expectation of DMA capability and carry a well-established precedent that an absent "dma-ranges" implies the same as the empty property, so we automatically opt those in to DMA configuration regardless, to avoid regressing most existing platforms. Fixes: ("of/acpi: Configure dma operations at probe time for platform/amba/pci bus devices") Reported-by:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Robin Murphy <robin.murphy@arm.com> Acked-by:

Rob Herring <robh@kernel.org> Signed-off-by:

Christoph Hellwig <hch@lst.de>

drivers/of/device.c

+32 −16

Original line number	Diff line number	Diff line
		@@ -9,6 +9,9 @@
		#include <linux/module.h>
		#include <linux/mod_devicetable.h>
		#include <linux/slab.h>
		#include <linux/pci.h>
		#include <linux/platform_device.h>
		#include <linux/amba/bus.h>

		#include <asm/errno.h>
		#include "of_private.h"
		@@ -84,31 +87,28 @@ int of_device_add(struct platform_device *ofdev)
		*/
		int of_dma_configure(struct device dev, struct device_node np)
		{
		u64 dma_addr, paddr, size;
		u64 dma_addr, paddr, size = 0;
		int ret;
		bool coherent;
		unsigned long offset;
		const struct iommu_ops *iommu;
		u64 mask;

		ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
		if (ret < 0) {
		/*
		* Set default coherent_dma_mask to 32 bit. Drivers are expected to
		* setup the correct supported mask.
		*/
		if (!dev->coherent_dma_mask)
		dev->coherent_dma_mask = DMA_BIT_MASK(32);

		/*
		* Set it to coherent_dma_mask by default if the architecture
		* code has not set it.
		* For legacy reasons, we have to assume some devices need
		* DMA configuration regardless of whether "dma-ranges" is
		* correctly specified or not.
		*/
		if (!dev->dma_mask)
		dev->dma_mask = &dev->coherent_dma_mask;
		if (!dev_is_pci(dev) &&
		#ifdef CONFIG_ARM_AMBA
		dev->bus != &amba_bustype &&
		#endif
		dev->bus != &platform_bus_type)
		return ret == -ENODEV ? 0 : ret;

		ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
		if (ret < 0) {
		dma_addr = offset = 0;
		size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
		} else {
		offset = PFN_DOWN(paddr - dma_addr);

		@@ -129,6 +129,22 @@ int of_dma_configure(struct device dev, struct device_node np)
		dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
		}

		/*
		* Set default coherent_dma_mask to 32 bit. Drivers are expected to
		* setup the correct supported mask.
		*/
		if (!dev->coherent_dma_mask)
		dev->coherent_dma_mask = DMA_BIT_MASK(32);
		/*
		* Set it to coherent_dma_mask by default if the architecture
		* code has not set it.
		*/
		if (!dev->dma_mask)
		dev->dma_mask = &dev->coherent_dma_mask;

		if (!size)
		size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);

		dev->dma_pfn_offset = offset;

		/*

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