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Subject[RFC][PATCH] misc: sram: Add dma-heap-export reserved SRAM area type
Date
This new export type exposes to userspace the SRAM area as a DMA-Heap,
this allows for allocations as DMA-BUFs that can be consumed by various
DMA-BUF supporting devices.

Signed-off-by: Andrew F. Davis <afd@ti.com>
---

Hello all,

This is an example user of the currently RFC DMA-HEAP framework. It
exports a defined SRAM area showing how various memory presenting
devices can use the DMA-HEAP framework to provide DMA-BUF allocations
to userspace and other devices.

It has a couple problems still, one being that the SRAM subsystem
probes before the DMA-BUF subsystem, can the SRAM driver be changed
from postcore_initcall to subsys_initcall or even device_initcall?

Thanks,
Andrew

.../devicetree/bindings/sram/sram.txt | 7 +-
drivers/misc/Kconfig | 7 +
drivers/misc/Makefile | 1 +
drivers/misc/sram-dma-heap.c | 235 ++++++++++++++++++
drivers/misc/sram.c | 20 +-
drivers/misc/sram.h | 17 ++
6 files changed, 282 insertions(+), 5 deletions(-)
create mode 100644 drivers/misc/sram-dma-heap.c

diff --git a/Documentation/devicetree/bindings/sram/sram.txt b/Documentation/devicetree/bindings/sram/sram.txt
index e98908bd4227..c5584f1f6ae8 100644
--- a/Documentation/devicetree/bindings/sram/sram.txt
+++ b/Documentation/devicetree/bindings/sram/sram.txt
@@ -43,11 +43,16 @@ Optional properties in the area nodes:
- export : indicates that the reserved SRAM area may be accessed outside
of the kernel, e.g. by bootloader or userspace
- protect-exec : Same as 'pool' above but with the additional
- constraint that code wil be run from the region and
+ constraint that code will be run from the region and
that the memory is maintained as read-only, executable
during code execution. NOTE: This region must be page
aligned on start and end in order to properly allow
manipulation of the page attributes.
+- dma-heap-export : Similar to 'pool' and 'export' this region will be
+ exported for use by drivers, devices, and userspace
+ using the DMA-Heaps framework. NOTE: This region must
+ be page aligned on start and end in order to properly
+ allow manipulation of the page attributes.
- label : the name for the reserved partition, if omitted, the label
is taken from the node name excluding the unit address.
- clocks : a list of phandle and clock specifier pair that controls the
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 42ab8ec92a04..5e655890458d 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -487,6 +487,13 @@ config SRAM
config SRAM_EXEC
bool

+config SRAM_DMA_HEAP
+ bool "Export on-chip SRAM pools using DMA-Heaps"
+ depends on SRAM
+ help
+ This driver allows the export of on-chip SRAM marked as exportable
+ to userspace using the DMA-Heaps interface.
+
config VEXPRESS_SYSCFG
bool "Versatile Express System Configuration driver"
depends on VEXPRESS_CONFIG
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index d5b7d3404dc7..f9db5326e0f7 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -49,6 +49,7 @@ obj-$(CONFIG_VMWARE_VMCI) += vmw_vmci/
obj-$(CONFIG_LATTICE_ECP3_CONFIG) += lattice-ecp3-config.o
obj-$(CONFIG_SRAM) += sram.o
obj-$(CONFIG_SRAM_EXEC) += sram-exec.o
+obj-$(CONFIG_SRAM_DMA_HEAP) += sram-dma-heap.o
obj-y += mic/
obj-$(CONFIG_GENWQE) += genwqe/
obj-$(CONFIG_ECHO) += echo/
diff --git a/drivers/misc/sram-dma-heap.c b/drivers/misc/sram-dma-heap.c
new file mode 100644
index 000000000000..bc930fced648
--- /dev/null
+++ b/drivers/misc/sram-dma-heap.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SRAM DMA-Heaps userspace exporter
+ *
+ * Copyright (C) 2019 Texas Instruments Incorporated - http://www.ti.com/
+ * Andrew F. Davis <afd@ti.com>
+ */
+
+#include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/genalloc.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <linux/scatterlist.h>
+#include <linux/slab.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-heap.h>
+
+#include "sram.h"
+
+struct sram_dma_heap {
+ struct dma_heap heap;
+ struct gen_pool *pool;
+};
+
+struct sram_dma_heap_buffer {
+ struct gen_pool *pool;
+ struct list_head attachments;
+ struct mutex attachments_lock;
+ unsigned long len;
+ unsigned long vaddr;
+ phys_addr_t paddr;
+};
+
+struct dma_heaps_attachment {
+ struct device *dev;
+ struct sg_table *table;
+ struct list_head list;
+};
+
+static int dma_heap_attach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *attachment)
+{
+ struct sram_dma_heap_buffer *buffer = dmabuf->priv;
+ struct dma_heaps_attachment *a;
+ struct sg_table *table;
+
+ a = kzalloc(sizeof(*a), GFP_KERNEL);
+ if (!a)
+ return -ENOMEM;
+
+ table = kmalloc(sizeof(*table), GFP_KERNEL);
+ if (!table) {
+ kfree(a);
+ return -ENOMEM;
+ }
+ if (sg_alloc_table(table, 1, GFP_KERNEL)) {
+ kfree(a);
+ return -ENOMEM;
+ }
+ sg_set_page(table->sgl, pfn_to_page(PFN_DOWN(buffer->paddr)), buffer->len, 0);
+
+ a->table = table;
+ a->dev = attachment->dev;
+ INIT_LIST_HEAD(&a->list);
+
+ attachment->priv = a;
+
+ mutex_lock(&buffer->attachments_lock);
+ list_add(&a->list, &buffer->attachments);
+ mutex_unlock(&buffer->attachments_lock);
+
+ return 0;
+}
+
+static void dma_heap_detatch(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *attachment)
+{
+ struct sram_dma_heap_buffer *buffer = dmabuf->priv;
+ struct dma_heaps_attachment *a = attachment->priv;
+
+ mutex_lock(&buffer->attachments_lock);
+ list_del(&a->list);
+ mutex_unlock(&buffer->attachments_lock);
+
+ sg_free_table(a->table);
+ kfree(a->table);
+ kfree(a);
+}
+
+static struct sg_table *dma_heap_map_dma_buf(struct dma_buf_attachment *attachment,
+ enum dma_data_direction direction)
+{
+ struct dma_heaps_attachment *a = attachment->priv;
+ struct sg_table *table = a->table;
+
+ if (!dma_map_sg_attrs(attachment->dev, table->sgl, table->nents,
+ direction, DMA_ATTR_SKIP_CPU_SYNC))
+ return ERR_PTR(-ENOMEM);
+
+ return table;
+}
+
+static void dma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
+ struct sg_table *table,
+ enum dma_data_direction direction)
+{
+ dma_unmap_sg_attrs(attachment->dev, table->sgl, table->nents,
+ direction, DMA_ATTR_SKIP_CPU_SYNC);
+}
+
+static void dma_heap_dma_buf_release(struct dma_buf *dmabuf)
+{
+ struct sram_dma_heap_buffer *buffer = dmabuf->priv;
+
+ gen_pool_free(buffer->pool, buffer->vaddr, buffer->len);
+ kfree(buffer);
+}
+
+static void *dma_heap_kmap(struct dma_buf *dmabuf, unsigned long page_num)
+{
+ struct sram_dma_heap_buffer *buffer = dmabuf->priv;
+
+ return (void *)buffer->vaddr + (page_num * PAGE_SIZE);
+}
+
+static int dma_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
+{
+ struct sram_dma_heap_buffer *buffer = dmabuf->priv;
+ int ret;
+
+ /* SRAM mappings are not cached */
+ vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
+ ret = vm_iomap_memory(vma, buffer->paddr, buffer->len);
+ if (ret)
+ pr_err("Could not map buffer to userspace\n");
+
+ return ret;
+}
+
+const struct dma_buf_ops sram_dma_heap_buf_ops = {
+ .attach = dma_heap_attach,
+ .detach = dma_heap_detatch,
+ .map_dma_buf = dma_heap_map_dma_buf,
+ .unmap_dma_buf = dma_heap_unmap_dma_buf,
+ .release = dma_heap_dma_buf_release,
+ .map = dma_heap_kmap,
+ .mmap = dma_heap_mmap,
+};
+
+static int sram_dma_heap_allocate(struct dma_heap *heap,
+ unsigned long len,
+ unsigned long flags)
+{
+ struct sram_dma_heap *sram_dma_heap = container_of(heap, struct sram_dma_heap, heap);
+ struct sram_dma_heap_buffer *buffer;
+
+ DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+ struct dma_buf *dmabuf;
+ int ret;
+
+ buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+ if (!buffer)
+ return -ENOMEM;
+ buffer->pool = sram_dma_heap->pool;
+ INIT_LIST_HEAD(&buffer->attachments);
+ mutex_init(&buffer->attachments_lock);
+ buffer->len = len;
+
+ buffer->vaddr = gen_pool_alloc(buffer->pool, buffer->len);
+ if (!buffer->vaddr) {
+ ret = -ENOMEM;
+ goto free_buffer;
+ }
+
+ buffer->paddr = gen_pool_virt_to_phys(buffer->pool, buffer->vaddr);
+ if (buffer->paddr == -1) {
+ ret = -ENOMEM;
+ goto free_pool;
+ }
+
+ /* create the dmabuf */
+ exp_info.ops = &sram_dma_heap_buf_ops;
+ exp_info.size = buffer->len;
+ exp_info.flags = O_RDWR;
+ exp_info.priv = buffer;
+ dmabuf = dma_buf_export(&exp_info);
+ if (IS_ERR(dmabuf)) {
+ ret = PTR_ERR(dmabuf);
+ goto free_pool;
+ }
+
+ ret = dma_buf_fd(dmabuf, O_CLOEXEC);
+ if (ret < 0) {
+ dma_buf_put(dmabuf);
+ /* just return, as put will call release and that will free */
+ return ret;
+ }
+
+ return ret;
+
+free_pool:
+ gen_pool_free(buffer->pool, buffer->vaddr, buffer->len);
+free_buffer:
+ kfree(buffer);
+
+ return ret;
+}
+
+static struct dma_heap_ops sram_dma_heap_ops = {
+ .allocate = sram_dma_heap_allocate,
+};
+
+int sram_dma_heap_export(struct sram_dev *sram,
+ struct sram_reserve *block,
+ phys_addr_t start,
+ struct sram_partition *part)
+{
+ struct sram_dma_heap *sram_dma_heap;
+
+ dev_info(sram->dev, "Exporting SRAM pool '%s'\n", block->label);
+
+ sram_dma_heap = kzalloc(sizeof(*sram_dma_heap), GFP_KERNEL);
+ if (!sram_dma_heap)
+ return -ENOMEM;
+
+ sram_dma_heap->heap.name = block->label;
+ sram_dma_heap->heap.ops = &sram_dma_heap_ops;
+ sram_dma_heap->pool = part->pool;
+
+ dma_heap_add(&sram_dma_heap->heap);
+
+ return 0;
+}
diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
index 80d8cbe8c01a..d11a3ab7b9b2 100644
--- a/drivers/misc/sram.c
+++ b/drivers/misc/sram.c
@@ -122,6 +122,15 @@ static int sram_add_partition(struct sram_dev *sram, struct sram_reserve *block,
if (ret)
return ret;
}
+ if (block->dma_heap_export) {
+ ret = sram_add_pool(sram, block, start, part);
+ if (ret)
+ return ret;
+
+ ret = sram_dma_heap_export(sram, block, start, part);
+ if (ret)
+ return ret;
+ }
if (block->protect_exec) {
ret = sram_check_protect_exec(sram, block, part);
if (ret)
@@ -222,8 +231,11 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
if (of_find_property(child, "protect-exec", NULL))
block->protect_exec = true;

- if ((block->export || block->pool || block->protect_exec) &&
- block->size) {
+ if (of_find_property(child, "dma-heap-export", NULL))
+ block->dma_heap_export = true;
+
+ if ((block->export || block->pool || block->protect_exec ||
+ block->dma_heap_export) && block->size) {
exports++;

label = NULL;
@@ -285,8 +297,8 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
goto err_chunks;
}

- if ((block->export || block->pool || block->protect_exec) &&
- block->size) {
+ if ((block->export || block->pool || block->protect_exec ||
+ block->dma_heap_export) && block->size) {
ret = sram_add_partition(sram, block,
res->start + block->start);
if (ret) {
diff --git a/drivers/misc/sram.h b/drivers/misc/sram.h
index c181ce4c8fca..c1eef4c32152 100644
--- a/drivers/misc/sram.h
+++ b/drivers/misc/sram.h
@@ -35,6 +35,7 @@ struct sram_reserve {
bool export;
bool pool;
bool protect_exec;
+ bool dma_heap_export;
const char *label;
};

@@ -55,4 +56,20 @@ static inline int sram_add_protect_exec(struct sram_partition *part)
return -ENODEV;
}
#endif /* CONFIG_SRAM_EXEC */
+
+#ifdef CONFIG_SRAM_DMA_HEAP
+int sram_dma_heap_export(struct sram_dev *sram,
+ struct sram_reserve *block,
+ phys_addr_t start,
+ struct sram_partition *part);
+#else
+static inline int sram_dma_heap_export(struct sram_dev *sram,
+ struct sram_reserve *block,
+ phys_addr_t start,
+ struct sram_partition *part)
+{
+ return 0;
+}
+#endif /* CONFIG_SRAM_DMA_HEAP */
+
#endif /* __SRAM_H */
--
2.21.0
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