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Subject[PATCH v2] staging: vc04_services: Replace dmac_map_area with dmac_map_sg
Date
The original arm implementation uses dmac_map_area which is not
portable. Replace it with an architecture neutral version
which uses dma_map_sg.

As you can see that for larger page sizes, the dma_map_sg
implementation is faster then the original unportable dma_map_area
implementation.

Test dmac_map_area dma_map_page dma_map_sg
vchiq_test -b 4 10000 51us/iter 76us/iter 76us
vchiq_test -b 8 10000 70us/iter 82us/iter 91us
vchiq_test -b 16 10000 94us/iter 118us/iter 121us
vchiq_test -b 32 10000 146us/iter 173us/iter 187us
vchiq_test -b 64 10000 263us/iter 328us/iter 299us
vchiq_test -b 128 10000 529us/iter 631us/iter 595us
vchiq_test -b 256 10000 2285us/iter 2275us/iter 2001us
vchiq_test -b 512 10000 4372us/iter 4616us/iter 4123us

For message sizes >= 64KB, dma_map_sg is faster then dma_map_page.

For message size >= 256KB, the dma_map_sg is the fastest
implementation.

"Normal" messages sizes should be about 1MB which is beyond
the length that this change shows a speed increase.

This is v2 of the patch which includes extra WARN_ONs and
incorporates feedback from Eric Anholt <eric@anholt.net>.

Signed-off-by: Michael Zoran <mzoran@crowfest.net>
---
.../interface/vchiq_arm/vchiq_2835_arm.c | 152 +++++++++++++--------
1 file changed, 93 insertions(+), 59 deletions(-)

diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
index 32d12e6..a5afcc5 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
@@ -45,13 +45,8 @@
#include <asm/pgtable.h>
#include <soc/bcm2835/raspberrypi-firmware.h>

-#define dmac_map_area __glue(_CACHE,_dma_map_area)
-#define dmac_unmap_area __glue(_CACHE,_dma_unmap_area)
-
#define TOTAL_SLOTS (VCHIQ_SLOT_ZERO_SLOTS + 2 * 32)

-#define VCHIQ_ARM_ADDRESS(x) ((void *)((char *)x + g_virt_to_bus_offset))
-
#include "vchiq_arm.h"
#include "vchiq_2835.h"
#include "vchiq_connected.h"
@@ -73,7 +68,7 @@ static unsigned int g_fragments_size;
static char *g_fragments_base;
static char *g_free_fragments;
static struct semaphore g_free_fragments_sema;
-static unsigned long g_virt_to_bus_offset;
+static struct device *g_dev;

extern int vchiq_arm_log_level;

@@ -84,10 +79,11 @@ vchiq_doorbell_irq(int irq, void *dev_id);

static int
create_pagelist(char __user *buf, size_t count, unsigned short type,
- struct task_struct *task, PAGELIST_T ** ppagelist);
+ struct task_struct *task, PAGELIST_T **ppagelist,
+ dma_addr_t *dma_addr);

static void
-free_pagelist(PAGELIST_T *pagelist, int actual);
+free_pagelist(dma_addr_t dma_addr, PAGELIST_T *pagelist, int actual);

int vchiq_platform_init(struct platform_device *pdev, VCHIQ_STATE_T *state)
{
@@ -101,8 +97,6 @@ int vchiq_platform_init(struct platform_device *pdev, VCHIQ_STATE_T *state)
int slot_mem_size, frag_mem_size;
int err, irq, i;

- g_virt_to_bus_offset = virt_to_dma(dev, (void *)0);
-
(void)of_property_read_u32(dev->of_node, "cache-line-size",
&g_cache_line_size);
g_fragments_size = 2 * g_cache_line_size;
@@ -118,7 +112,7 @@ int vchiq_platform_init(struct platform_device *pdev, VCHIQ_STATE_T *state)
return -ENOMEM;
}

- WARN_ON(((int)slot_mem & (PAGE_SIZE - 1)) != 0);
+ WARN_ON(((unsigned long)slot_mem & (PAGE_SIZE - 1)) != 0);

vchiq_slot_zero = vchiq_init_slots(slot_mem, slot_mem_size);
if (!vchiq_slot_zero)
@@ -170,6 +164,7 @@ int vchiq_platform_init(struct platform_device *pdev, VCHIQ_STATE_T *state)
return err ? : -ENXIO;
}

+ g_dev = dev;
vchiq_log_info(vchiq_arm_log_level,
"vchiq_init - done (slots %pK, phys %pad)",
vchiq_slot_zero, &slot_phys);
@@ -233,6 +228,7 @@ vchiq_prepare_bulk_data(VCHIQ_BULK_T *bulk, VCHI_MEM_HANDLE_T memhandle,
{
PAGELIST_T *pagelist;
int ret;
+ dma_addr_t dma_addr;

WARN_ON(memhandle != VCHI_MEM_HANDLE_INVALID);

@@ -241,12 +237,14 @@ vchiq_prepare_bulk_data(VCHIQ_BULK_T *bulk, VCHI_MEM_HANDLE_T memhandle,
? PAGELIST_READ
: PAGELIST_WRITE,
current,
- &pagelist);
+ &pagelist,
+ &dma_addr);
+
if (ret != 0)
return VCHIQ_ERROR;

bulk->handle = memhandle;
- bulk->data = VCHIQ_ARM_ADDRESS(pagelist);
+ bulk->data = (void *)(unsigned long)dma_addr;

/* Store the pagelist address in remote_data, which isn't used by the
slave. */
@@ -259,7 +257,8 @@ void
vchiq_complete_bulk(VCHIQ_BULK_T *bulk)
{
if (bulk && bulk->remote_data && bulk->actual)
- free_pagelist((PAGELIST_T *)bulk->remote_data, bulk->actual);
+ free_pagelist((dma_addr_t)(unsigned long)bulk->data,
+ (PAGELIST_T *)bulk->remote_data, bulk->actual);
}

void
@@ -353,38 +352,44 @@ vchiq_doorbell_irq(int irq, void *dev_id)
** obscuring the new data underneath. We can solve this by transferring the
** partial cache lines separately, and allowing the ARM to copy into the
** cached area.
-
-** N.B. This implementation plays slightly fast and loose with the Linux
-** driver programming rules, e.g. its use of dmac_map_area instead of
-** dma_map_single, but it isn't a multi-platform driver and it benefits
-** from increased speed as a result.
*/

static int
create_pagelist(char __user *buf, size_t count, unsigned short type,
- struct task_struct *task, PAGELIST_T ** ppagelist)
+ struct task_struct *task, PAGELIST_T **ppagelist,
+ dma_addr_t *dma_addr)
{
PAGELIST_T *pagelist;
struct page **pages;
- unsigned long *addrs;
- unsigned int num_pages, offset, i;
- char *addr, *base_addr, *next_addr;
- int run, addridx, actual_pages;
+ u32 *addrs;
+ unsigned int num_pages, offset, i, k;
+ int actual_pages;
unsigned long *need_release;
+ size_t pagelist_size;
+ struct scatterlist *scatterlist, *sg;
+ int dma_buffers;
+ int dir;

- offset = (unsigned int)buf & (PAGE_SIZE - 1);
+ offset = ((unsigned int)(unsigned long)buf & (PAGE_SIZE - 1));
num_pages = (count + offset + PAGE_SIZE - 1) / PAGE_SIZE;

+ pagelist_size = sizeof(PAGELIST_T) +
+ (num_pages * sizeof(unsigned long)) +
+ sizeof(unsigned long) +
+ (num_pages * sizeof(pages[0]) +
+ (num_pages * sizeof(struct scatterlist)));
+
*ppagelist = NULL;

+ dir = (type == PAGELIST_WRITE) ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+
/* Allocate enough storage to hold the page pointers and the page
** list
*/
- pagelist = kmalloc(sizeof(PAGELIST_T) +
- (num_pages * sizeof(unsigned long)) +
- sizeof(unsigned long) +
- (num_pages * sizeof(pages[0])),
- GFP_KERNEL);
+ pagelist = dma_zalloc_coherent(g_dev,
+ pagelist_size,
+ dma_addr,
+ GFP_KERNEL);

vchiq_log_trace(vchiq_arm_log_level, "create_pagelist - %pK",
pagelist);
@@ -394,10 +399,9 @@ create_pagelist(char __user *buf, size_t count, unsigned short type,
addrs = pagelist->addrs;
need_release = (unsigned long *)(addrs + num_pages);
pages = (struct page **)(addrs + num_pages + 1);
+ scatterlist = (struct scatterlist *)(pages + num_pages);

if (is_vmalloc_addr(buf)) {
- int dir = (type == PAGELIST_WRITE) ?
- DMA_TO_DEVICE : DMA_FROM_DEVICE;
unsigned long length = count;
unsigned int off = offset;

@@ -410,7 +414,6 @@ create_pagelist(char __user *buf, size_t count, unsigned short type,
if (bytes > length)
bytes = length;
pages[actual_pages] = pg;
- dmac_map_area(page_address(pg) + off, bytes, dir);
length -= bytes;
off = 0;
}
@@ -438,7 +441,8 @@ create_pagelist(char __user *buf, size_t count, unsigned short type,
actual_pages--;
put_page(pages[actual_pages]);
}
- kfree(pagelist);
+ dma_free_coherent(g_dev, pagelist_size,
+ pagelist, *dma_addr);
if (actual_pages == 0)
actual_pages = -ENOMEM;
return actual_pages;
@@ -450,30 +454,44 @@ create_pagelist(char __user *buf, size_t count, unsigned short type,
pagelist->type = type;
pagelist->offset = offset;

- /* Group the pages into runs of contiguous pages */
+ for (i = 0; i < num_pages; i++)
+ sg_set_page(scatterlist + i, pages[i], PAGE_SIZE, 0);
+
+ dma_buffers = dma_map_sg(g_dev,
+ scatterlist,
+ num_pages,
+ dir);

- base_addr = VCHIQ_ARM_ADDRESS(page_address(pages[0]));
- next_addr = base_addr + PAGE_SIZE;
- addridx = 0;
- run = 0;
+ if (dma_buffers == 0) {
+ dma_free_coherent(g_dev, pagelist_size,
+ pagelist, *dma_addr);

- for (i = 1; i < num_pages; i++) {
- addr = VCHIQ_ARM_ADDRESS(page_address(pages[i]));
- if ((addr == next_addr) && (run < (PAGE_SIZE - 1))) {
- next_addr += PAGE_SIZE;
- run++;
+ return -EINTR;
+ }
+
+ /* Combine adjacent blocks for performance */
+ k = 0;
+ for_each_sg(scatterlist, sg, dma_buffers, i) {
+ u32 len = sg_dma_len(sg);
+ u32 addr = sg_dma_address(sg);
+
+ /* Note: addrs is the address + page_count - 1
+ * The firmware expects the block to be page
+ * aligned and a multiple of the page size
+ */
+ WARN_ON(len == 0);
+ WARN_ON(len & ~PAGE_MASK);
+ WARN_ON(addr & ~PAGE_MASK);
+ if (k > 0 &&
+ ((addrs[k - 1] & PAGE_MASK) |
+ ((addrs[k - 1] & ~PAGE_MASK) + 1) << PAGE_SHIFT)
+ == addr) {
+ addrs[k - 1] += (len >> PAGE_SHIFT);
} else {
- addrs[addridx] = (unsigned long)base_addr + run;
- addridx++;
- base_addr = addr;
- next_addr = addr + PAGE_SIZE;
- run = 0;
+ addrs[k++] = addr | ((len >> PAGE_SHIFT) - 1);
}
}

- addrs[addridx] = (unsigned long)base_addr + run;
- addridx++;
-
/* Partial cache lines (fragments) require special measures */
if ((type == PAGELIST_READ) &&
((pagelist->offset & (g_cache_line_size - 1)) ||
@@ -482,7 +500,10 @@ create_pagelist(char __user *buf, size_t count, unsigned short type,
char *fragments;

if (down_interruptible(&g_free_fragments_sema) != 0) {
- kfree(pagelist);
+ dma_unmap_sg(g_dev, scatterlist, num_pages,
+ DMA_BIDIRECTIONAL);
+ dma_free_coherent(g_dev, pagelist_size,
+ pagelist, *dma_addr);
return -EINTR;
}

@@ -497,29 +518,42 @@ create_pagelist(char __user *buf, size_t count, unsigned short type,
(fragments - g_fragments_base) / g_fragments_size;
}

- dmac_flush_range(pagelist, addrs + num_pages);
-
*ppagelist = pagelist;

return 0;
}

static void
-free_pagelist(PAGELIST_T *pagelist, int actual)
+free_pagelist(dma_addr_t dma_addr, PAGELIST_T *pagelist, int actual)
{
unsigned long *need_release;
struct page **pages;
unsigned int num_pages, i;
+ size_t pagelist_size;
+ struct scatterlist *scatterlist;
+ int dir;

vchiq_log_trace(vchiq_arm_log_level, "free_pagelist - %pK, %d",
pagelist, actual);

+ dir = (pagelist->type == PAGELIST_WRITE) ? DMA_TO_DEVICE :
+ DMA_FROM_DEVICE;
+
num_pages =
(pagelist->length + pagelist->offset + PAGE_SIZE - 1) /
PAGE_SIZE;

+ pagelist_size = sizeof(PAGELIST_T) +
+ (num_pages * sizeof(unsigned long)) +
+ sizeof(unsigned long) +
+ (num_pages * sizeof(pages[0]) +
+ (num_pages * sizeof(struct scatterlist)));
+
need_release = (unsigned long *)(pagelist->addrs + num_pages);
pages = (struct page **)(pagelist->addrs + num_pages + 1);
+ scatterlist = (struct scatterlist *)(pages + num_pages);
+
+ dma_unmap_sg(g_dev, scatterlist, num_pages, dir);

/* Deal with any partial cache lines (fragments) */
if (pagelist->type >= PAGELIST_READ_WITH_FRAGMENTS) {
@@ -569,8 +603,7 @@ free_pagelist(PAGELIST_T *pagelist, int actual)

if (bytes > length)
bytes = length;
- dmac_unmap_area(page_address(pg) + offset,
- bytes, DMA_FROM_DEVICE);
+
length -= bytes;
offset = 0;
set_page_dirty(pg);
@@ -579,5 +612,6 @@ free_pagelist(PAGELIST_T *pagelist, int actual)
}
}

- kfree(pagelist);
+ dma_free_coherent(g_dev, pagelist_size,
+ pagelist, dma_addr);
}
--
2.10.1
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