[RFC PATCH 1/3] ARM: NOMMU: introduce dma operations for noMMU
Vladimir Murzin
vladimir.murzin at arm.com
Tue Dec 13 01:02:19 PST 2016
R/M classes of cpus can have momory 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 introduces the way to specify region of memory (via
"memdma=size at start" command line option) suitable for consistent DMA
operations. It is supposed that such region is marked by MPU as
non-cacheable.
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. In case cpu
supports caches and no coherent memory region is given - dma is
disallowed.
Reported-by: Alexandre Torgue <alexandre.torgue at st.com>
Reported-by: Andras Szemzo <sza at esh.hu>
Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
---
arch/arm/include/asm/dma-mapping.h | 3 +-
arch/arm/mm/Makefile | 5 +-
arch/arm/mm/dma-mapping-nommu.c | 262 ++++++++++++++++++++++++++++++++++++
arch/arm/mm/mm.h | 3 +
arch/arm/mm/nommu.c | 8 ++
5 files changed, 277 insertions(+), 4 deletions(-)
create mode 100644 arch/arm/mm/dma-mapping-nommu.c
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index bf02dbd..559faad 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -20,7 +20,8 @@ static inline struct dma_map_ops *__generic_dma_ops(struct device *dev)
{
if (dev && dev->archdata.dma_ops)
return dev->archdata.dma_ops;
- return &arm_dma_ops;
+
+ return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_noop_ops;
}
static inline struct dma_map_ops *get_dma_ops(struct device *dev)
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 2ac7988..5796357 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -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
diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
new file mode 100644
index 0000000..b24228e
--- /dev/null
+++ b/arch/arm/mm/dma-mapping-nommu.c
@@ -0,0 +1,262 @@
+/*
+ * 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.
+ *
+ * DMA uncached mapping support.
+ */
+
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+#include <linux/genalloc.h>
+
+#include <asm/cachetype.h>
+#include <asm/cacheflush.h>
+#include <asm/outercache.h>
+
+#include "dma.h"
+
+unsigned long dma_start __initdata;
+unsigned long dma_size __initdata;
+
+static struct gen_pool *dma_pool;
+
+static void *arm_nommu_dma_alloc(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t gfp,
+ unsigned long attrs)
+{
+ void *ptr;
+
+ if (!dma_pool)
+ return NULL;
+
+ ptr = (void *)gen_pool_alloc(dma_pool, size);
+ if (ptr) {
+ *dma_handle = __pa(ptr);
+ dmac_flush_range(ptr, ptr + size);
+ outer_flush_range(__pa(ptr), __pa(ptr) + size);
+ }
+
+ return ptr;
+}
+
+static void arm_nommu_dma_free(struct device *dev, size_t size,
+ void *cpu_addr, dma_addr_t dma_addr,
+ unsigned long attrs)
+{
+ gen_pool_free(dma_pool, (unsigned long)cpu_addr, size);
+}
+
+static void __dma_page_cpu_to_dev(dma_addr_t handle, size_t size,
+ enum dma_data_direction dir)
+{
+ dmac_unmap_area(__va(handle), size, dir);
+
+ if (dir == DMA_FROM_DEVICE)
+ outer_inv_range(handle, handle + size);
+ else
+ outer_clean_range(handle, handle + size);
+}
+
+static void __dma_page_dev_to_cpu(dma_addr_t handle, size_t size,
+ enum dma_data_direction dir)
+{
+ if (dir != DMA_TO_DEVICE) {
+ outer_inv_range(handle, handle + size);
+ dmac_unmap_area(__va(handle), 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);
+}
+
+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 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)
+{
+ struct dma_map_ops *dma_ops;
+
+ /*
+ * Cahe support for v7m is optional, so can be treated as
+ * coherent if no cache has been detected.
+ */
+ dev->archdata.dma_coherent = (cacheid) ? 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)
+{
+}
+
+int dma_supported(struct device *dev, u64 mask)
+{
+ if (cacheid && !dma_pool)
+ return 0;
+
+ return 1;
+}
+
+EXPORT_SYMBOL(dma_supported);
+
+#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);
+
+/*
+ * Initialise the coherent pool for DMA allocations.
+ */
+static int __init dma_pool_init(void)
+{
+ int ret;
+
+ if (cacheid && !dma_size) {
+ pr_warn("DMA: coherent memory region has not been given.\n");
+ return 0;
+ }
+
+ dma_pool = gen_pool_create(PAGE_SHIFT, -1);
+
+ if (!dma_pool)
+ goto out;
+
+ ret = gen_pool_add_virt(dma_pool, (unsigned long)dma_start, (unsigned long)dma_start,
+ dma_size, -1);
+ if (ret)
+ goto destroy_genpool;
+
+ gen_pool_set_algo(dma_pool, gen_pool_first_fit_order_align, NULL);
+
+ pr_info("DMA: coherent memory region 0x%lx - 0x%lx (%lu KiB)\n",
+ dma_start, dma_start + dma_size, dma_size >> 10);
+
+ return 0;
+
+destroy_genpool:
+ gen_pool_destroy(dma_pool);
+ dma_pool = NULL;
+out:
+ pr_err("DMA: failed to allocate coherent memory region\n");
+ return -ENOMEM;
+}
+
+postcore_initcall(dma_pool_init);
+
+/* "memdma=<size>@<address>" parsing. */
+static int __init early_memdma(char *p)
+{
+ if (!p)
+ return -EINVAL;
+
+ dma_size = memparse(p, &p);
+ if (*p == '@')
+ dma_start = memparse(p + 1, &p);
+
+ return 0;
+}
+early_param("memdma", early_memdma);
diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
index ce727d4..18eb869 100644
--- a/arch/arm/mm/mm.h
+++ b/arch/arm/mm/mm.h
@@ -97,3 +97,6 @@ struct static_vm {
void dma_contiguous_remap(void);
unsigned long __clear_cr(unsigned long mask);
+
+extern unsigned long dma_start __initdata;
+extern unsigned long dma_size __initdata;
diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
index 681cec8..15487bb 100644
--- a/arch/arm/mm/nommu.c
+++ b/arch/arm/mm/nommu.c
@@ -294,15 +294,23 @@ void __init arm_mm_memblock_reserve(void)
* reserved here.
*/
#endif
+
}
void __init sanity_check_meminfo(void)
{
phys_addr_t end;
+
sanity_check_meminfo_mpu();
end = memblock_end_of_DRAM();
high_memory = __va(end - 1) + 1;
memblock_set_current_limit(end);
+
+ if (dma_size &&
+ memblock_overlaps_region(&memblock.memory, dma_start, dma_size)) {
+ pr_crit("DMA: coherent memory region overlaps with main memory.\n");
+ dma_size = 0;
+ }
}
/*
--
1.7.9.5
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