Commit 1c51c429 authored by Vladimir Murzin's avatar Vladimir Murzin Committed by Christoph Hellwig
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ARM: NOMMU: Introduce dma operations for noMMU 



R/M classes of cpus can have memory covered by MPU which in turn might
configure RAM as Normal i.e. bufferable and cacheable. It breaks
dma_alloc_coherent() and friends, since data can stuck in caches now
or be buffered.

This patch factors out DMA support for NOMMU configuration into
separate entity which provides dedicated dma_ops. We have to handle
there several cases:
- configurations with MMU/MPU setup
- configurations without MMU/MPU setup
- special case for M-class, since caches and MPU there are optional

In general we rely on default DMA area for coherent allocations or/and
per-device memory reserves suitable for coherent DMA, so if such
regions are set coherent allocations go from there.

In case MMU/MPU was not setup we fallback to normal page allocator for
DMA memory allocation.

In case we run M-class cpus, for configuration without cache support
(like Cortex-M3/M4) dma operations are forced to be coherent and wired
with dma-noop (such decision is made based on cacheid global
variable); however, if caches are detected there and no DMA coherent
region is given (either default or per-device), dma is disallowed even
MPU is not set - it is because M-class implement system memory map
which defines part of address space as Normal memory.

Reported-by: default avatarAlexandre Torgue <alexandre.torgue@st.com>
Reported-by: default avatarAndras Szemzo <sza@esh.hu>
Tested-by: default avatarBenjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: default avatarAndras Szemzo <sza@esh.hu>
Tested-by: default avatarAlexandre TORGUE <alexandre.torgue@st.com>
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarVladimir Murzin <vladimir.murzin@arm.com>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
[hch: removed the dma_supported() implementation that isn't required anymore]
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 07c75d7a

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ config ARM 
	select CLONE_BACKWARDS

	select CPU_PM if (SUSPEND || CPU_IDLE)

	select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS

	select DMA_NOOP_OPS if !MMU

	select EDAC_SUPPORT

	select EDAC_ATOMIC_SCRUB

	select GENERIC_ALLOCATOR

arch/arm/include/asm/dma-mapping.h

+1 −1
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ extern const struct dma_map_ops arm_coherent_dma_ops; 


static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)

{

	return &arm_dma_ops;

	return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_noop_ops;

}



#ifdef __arch_page_to_dma

arch/arm/mm/Makefile

+2 −3
Original line number Diff line number Diff line
@@ -2,9 +2,8 @@ 
# Makefile for the linux arm-specific parts of the memory manager.

#



obj-y				:= dma-mapping.o extable.o fault.o init.o \

				   iomap.o



obj-y				:= extable.o fault.o init.o iomap.o

obj-y				+= dma-mapping$(MMUEXT).o

obj-$(CONFIG_MMU)		+= fault-armv.o flush.o idmap.o ioremap.o \

				   mmap.o pgd.o mmu.o pageattr.o

arch/arm/mm/dma-mapping-nommu.c

0 → 100644
+228 −0
Original line number Diff line number Diff line 
/*

 *  Based on linux/arch/arm/mm/dma-mapping.c

 *

 *  Copyright (C) 2000-2004 Russell King

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 */



#include <linux/export.h>

#include <linux/mm.h>

#include <linux/dma-mapping.h>

#include <linux/scatterlist.h>



#include <asm/cachetype.h>

#include <asm/cacheflush.h>

#include <asm/outercache.h>

#include <asm/cp15.h>



#include "dma.h"



/*

 *  dma_noop_ops is used if

 *   - MMU/MPU is off

 *   - cpu is v7m w/o cache support

 *   - device is coherent

 *  otherwise arm_nommu_dma_ops is used.

 *

 *  arm_nommu_dma_ops rely on consistent DMA memory (please, refer to

 *  [1] on how to declare such memory).

 *

 *  [1] Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

 */



static void *arm_nommu_dma_alloc(struct device *dev, size_t size,

				 dma_addr_t *dma_handle, gfp_t gfp,

				 unsigned long attrs)



{

	const struct dma_map_ops *ops = &dma_noop_ops;



	/*

	 * We are here because:

	 * - no consistent DMA region has been defined, so we can't

	 *   continue.

	 * - there is no space left in consistent DMA region, so we

	 *   only can fallback to generic allocator if we are

	 *   advertised that consistency is not required.

	 */



	if (attrs & DMA_ATTR_NON_CONSISTENT)

		return ops->alloc(dev, size, dma_handle, gfp, attrs);



	WARN_ON_ONCE(1);

	return NULL;

}



static void arm_nommu_dma_free(struct device *dev, size_t size,

			       void *cpu_addr, dma_addr_t dma_addr,

			       unsigned long attrs)

{

	const struct dma_map_ops *ops = &dma_noop_ops;



	if (attrs & DMA_ATTR_NON_CONSISTENT)

		ops->free(dev, size, cpu_addr, dma_addr, attrs);

	else

		WARN_ON_ONCE(1);



	return;

}



static void __dma_page_cpu_to_dev(phys_addr_t paddr, size_t size,

				  enum dma_data_direction dir)

{

	dmac_map_area(__va(paddr), size, dir);



	if (dir == DMA_FROM_DEVICE)

		outer_inv_range(paddr, paddr + size);

	else

		outer_clean_range(paddr, paddr + size);

}



static void __dma_page_dev_to_cpu(phys_addr_t paddr, size_t size,

				  enum dma_data_direction dir)

{

	if (dir != DMA_TO_DEVICE) {

		outer_inv_range(paddr, paddr + size);

		dmac_unmap_area(__va(paddr), size, dir);

	}

}



static dma_addr_t arm_nommu_dma_map_page(struct device *dev, struct page *page,

					 unsigned long offset, size_t size,

					 enum dma_data_direction dir,

					 unsigned long attrs)

{

	dma_addr_t handle = page_to_phys(page) + offset;



	__dma_page_cpu_to_dev(handle, size, dir);



	return handle;

}



static void arm_nommu_dma_unmap_page(struct device *dev, dma_addr_t handle,

				     size_t size, enum dma_data_direction dir,

				     unsigned long attrs)

{

	__dma_page_dev_to_cpu(handle, size, dir);

}





static int arm_nommu_dma_map_sg(struct device *dev, struct scatterlist *sgl,

				int nents, enum dma_data_direction dir,

				unsigned long attrs)

{

	int i;

	struct scatterlist *sg;



	for_each_sg(sgl, sg, nents, i) {

		sg_dma_address(sg) = sg_phys(sg);

		sg_dma_len(sg) = sg->length;

		__dma_page_cpu_to_dev(sg_dma_address(sg), sg_dma_len(sg), dir);

	}



	return nents;

}



static void arm_nommu_dma_unmap_sg(struct device *dev, struct scatterlist *sgl,

				   int nents, enum dma_data_direction dir,

				   unsigned long attrs)

{

	struct scatterlist *sg;

	int i;



	for_each_sg(sgl, sg, nents, i)

		__dma_page_dev_to_cpu(sg_dma_address(sg), sg_dma_len(sg), dir);

}



static void arm_nommu_dma_sync_single_for_device(struct device *dev,

		dma_addr_t handle, size_t size, enum dma_data_direction dir)

{

	__dma_page_cpu_to_dev(handle, size, dir);

}



static void arm_nommu_dma_sync_single_for_cpu(struct device *dev,

		dma_addr_t handle, size_t size, enum dma_data_direction dir)

{

	__dma_page_cpu_to_dev(handle, size, dir);

}



static void arm_nommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,

					     int nents, enum dma_data_direction dir)

{

	struct scatterlist *sg;

	int i;



	for_each_sg(sgl, sg, nents, i)

		__dma_page_cpu_to_dev(sg_dma_address(sg), sg_dma_len(sg), dir);

}



static void arm_nommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,

					  int nents, enum dma_data_direction dir)

{

	struct scatterlist *sg;

	int i;



	for_each_sg(sgl, sg, nents, i)

		__dma_page_dev_to_cpu(sg_dma_address(sg), sg_dma_len(sg), dir);

}



const struct dma_map_ops arm_nommu_dma_ops = {

	.alloc			= arm_nommu_dma_alloc,

	.free			= arm_nommu_dma_free,

	.map_page		= arm_nommu_dma_map_page,

	.unmap_page		= arm_nommu_dma_unmap_page,

	.map_sg			= arm_nommu_dma_map_sg,

	.unmap_sg		= arm_nommu_dma_unmap_sg,

	.sync_single_for_device	= arm_nommu_dma_sync_single_for_device,

	.sync_single_for_cpu	= arm_nommu_dma_sync_single_for_cpu,

	.sync_sg_for_device	= arm_nommu_dma_sync_sg_for_device,

	.sync_sg_for_cpu	= arm_nommu_dma_sync_sg_for_cpu,

};

EXPORT_SYMBOL(arm_nommu_dma_ops);



static const struct dma_map_ops *arm_nommu_get_dma_map_ops(bool coherent)

{

	return coherent ? &dma_noop_ops : &arm_nommu_dma_ops;

}



void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,

			const struct iommu_ops *iommu, bool coherent)

{

	const struct dma_map_ops *dma_ops;



	if (IS_ENABLED(CONFIG_CPU_V7M)) {

		/*

		 * Cache support for v7m is optional, so can be treated as

		 * coherent if no cache has been detected. Note that it is not

		 * enough to check if MPU is in use or not since in absense of

		 * MPU system memory map is used.

		 */

		dev->archdata.dma_coherent = (cacheid) ? coherent : true;

	} else {

		/*

		 * Assume coherent DMA in case MMU/MPU has not been set up.

		 */

		dev->archdata.dma_coherent = (get_cr() & CR_M) ? coherent : true;

	}



	dma_ops = arm_nommu_get_dma_map_ops(dev->archdata.dma_coherent);



	set_dma_ops(dev, dma_ops);

}



void arch_teardown_dma_ops(struct device *dev)

{

}



#define PREALLOC_DMA_DEBUG_ENTRIES	4096



static int __init dma_debug_do_init(void)

{

	dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);

	return 0;

}

core_initcall(dma_debug_do_init);

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