Commit 98ccf149 authored by Pierre Ossman's avatar Pierre Ossman

mmc: bounce requests for simple hosts

Some hosts cannot do scatter/gather in hardware. Since not doing sg
is such a big performance hit, we (optionally) bounce the requests
to a simple linear buffer that we hand over to the driver.
Signed-off-by: default avatarPierre Ossman <drzeus@drzeus.cx>
parent 7dcca30a
......@@ -14,3 +14,21 @@ config MMC_BLOCK
mount the filesystem. Almost everyone wishing MMC support
should say Y or M here.
config MMC_BLOCK_BOUNCE
bool "Use bounce buffer for simple hosts"
depends on MMC_BLOCK
default y
help
SD/MMC is a high latency protocol where it is crucial to
send large requests in order to get high performance. Many
controllers, however, are restricted to continuous memory
(i.e. they can't do scatter-gather), something the kernel
rarely can provide.
Say Y here to help these restricted hosts by bouncing
requests back and forth from a large buffer. You will get
a big performance gain at the cost of up to 64 KiB of
physical memory.
If unsure, say Y here.
......@@ -262,7 +262,9 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
}
brq.data.sg = mq->sg;
brq.data.sg_len = blk_rq_map_sg(req->q, req, brq.data.sg);
brq.data.sg_len = mmc_queue_map_sg(mq);
mmc_queue_bounce_pre(mq);
if (brq.data.blocks !=
(req->nr_sectors >> (md->block_bits - 9))) {
......@@ -279,6 +281,9 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
}
mmc_wait_for_req(card->host, &brq.mrq);
mmc_queue_bounce_post(mq);
if (brq.cmd.error) {
printk(KERN_ERR "%s: error %d sending read/write command\n",
req->rq_disk->disk_name, brq.cmd.error);
......
......@@ -17,6 +17,8 @@
#include <linux/mmc/host.h>
#include "queue.h"
#define MMC_QUEUE_BOUNCESZ 65536
#define MMC_QUEUE_SUSPENDED (1 << 0)
/*
......@@ -118,6 +120,7 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card, spinlock_t *lock
struct mmc_host *host = card->host;
u64 limit = BLK_BOUNCE_HIGH;
int ret;
unsigned int bouncesz;
if (mmc_dev(host)->dma_mask && *mmc_dev(host)->dma_mask)
limit = *mmc_dev(host)->dma_mask;
......@@ -127,21 +130,61 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card, spinlock_t *lock
if (!mq->queue)
return -ENOMEM;
blk_queue_prep_rq(mq->queue, mmc_prep_request);
blk_queue_bounce_limit(mq->queue, limit);
blk_queue_max_sectors(mq->queue, host->max_req_size / 512);
blk_queue_max_phys_segments(mq->queue, host->max_phys_segs);
blk_queue_max_hw_segments(mq->queue, host->max_hw_segs);
blk_queue_max_segment_size(mq->queue, host->max_seg_size);
mq->queue->queuedata = mq;
mq->req = NULL;
mq->sg = kmalloc(sizeof(struct scatterlist) * host->max_phys_segs,
GFP_KERNEL);
if (!mq->sg) {
ret = -ENOMEM;
goto cleanup_queue;
blk_queue_prep_rq(mq->queue, mmc_prep_request);
#ifdef CONFIG_MMC_BLOCK_BOUNCE
if (host->max_hw_segs == 1) {
bouncesz = MMC_QUEUE_BOUNCESZ;
if (bouncesz > host->max_req_size)
bouncesz = host->max_req_size;
if (bouncesz > host->max_seg_size)
bouncesz = host->max_seg_size;
mq->bounce_buf = kmalloc(bouncesz, GFP_KERNEL);
if (!mq->bounce_buf) {
printk(KERN_WARNING "%s: unable to allocate "
"bounce buffer\n", mmc_card_name(card));
} else {
blk_queue_bounce_limit(mq->queue, BLK_BOUNCE_HIGH);
blk_queue_max_sectors(mq->queue, bouncesz / 512);
blk_queue_max_phys_segments(mq->queue, bouncesz / 512);
blk_queue_max_hw_segments(mq->queue, bouncesz / 512);
blk_queue_max_segment_size(mq->queue, bouncesz);
mq->sg = kmalloc(sizeof(struct scatterlist),
GFP_KERNEL);
if (!mq->sg) {
ret = -ENOMEM;
goto free_bounce_buf;
}
mq->bounce_sg = kmalloc(sizeof(struct scatterlist) *
bouncesz / 512, GFP_KERNEL);
if (!mq->bounce_sg) {
ret = -ENOMEM;
goto free_sg;
}
}
}
#endif
if (!mq->bounce_buf) {
blk_queue_bounce_limit(mq->queue, limit);
blk_queue_max_sectors(mq->queue, host->max_req_size / 512);
blk_queue_max_phys_segments(mq->queue, host->max_phys_segs);
blk_queue_max_hw_segments(mq->queue, host->max_hw_segs);
blk_queue_max_segment_size(mq->queue, host->max_seg_size);
mq->sg = kmalloc(sizeof(struct scatterlist) *
host->max_phys_segs, GFP_KERNEL);
if (!mq->sg) {
ret = -ENOMEM;
goto cleanup_queue;
}
}
init_MUTEX(&mq->thread_sem);
......@@ -149,14 +192,21 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card, spinlock_t *lock
mq->thread = kthread_run(mmc_queue_thread, mq, "mmcqd");
if (IS_ERR(mq->thread)) {
ret = PTR_ERR(mq->thread);
goto free_sg;
goto free_bounce_sg;
}
return 0;
free_bounce_sg:
if (mq->bounce_sg)
kfree(mq->bounce_sg);
mq->bounce_sg = NULL;
free_sg:
kfree(mq->sg);
mq->sg = NULL;
free_bounce_buf:
if (mq->bounce_buf)
kfree(mq->bounce_buf);
mq->bounce_buf = NULL;
cleanup_queue:
blk_cleanup_queue(mq->queue);
return ret;
......@@ -178,9 +228,17 @@ void mmc_cleanup_queue(struct mmc_queue *mq)
/* Then terminate our worker thread */
kthread_stop(mq->thread);
if (mq->bounce_sg)
kfree(mq->bounce_sg);
mq->bounce_sg = NULL;
kfree(mq->sg);
mq->sg = NULL;
if (mq->bounce_buf)
kfree(mq->bounce_buf);
mq->bounce_buf = NULL;
blk_cleanup_queue(mq->queue);
mq->card = NULL;
......@@ -231,3 +289,108 @@ void mmc_queue_resume(struct mmc_queue *mq)
}
}
static void copy_sg(struct scatterlist *dst, unsigned int dst_len,
struct scatterlist *src, unsigned int src_len)
{
unsigned int chunk;
char *dst_buf, *src_buf;
unsigned int dst_size, src_size;
dst_buf = NULL;
src_buf = NULL;
dst_size = 0;
src_size = 0;
while (src_len) {
BUG_ON(dst_len == 0);
if (dst_size == 0) {
dst_buf = page_address(dst->page) + dst->offset;
dst_size = dst->length;
}
if (src_size == 0) {
src_buf = page_address(src->page) + src->offset;
src_size = src->length;
}
chunk = min(dst_size, src_size);
memcpy(dst_buf, src_buf, chunk);
dst_buf += chunk;
src_buf += chunk;
dst_size -= chunk;
src_size -= chunk;
if (dst_size == 0) {
dst++;
dst_len--;
}
if (src_size == 0) {
src++;
src_len--;
}
}
}
unsigned int mmc_queue_map_sg(struct mmc_queue *mq)
{
unsigned int sg_len;
if (!mq->bounce_buf)
return blk_rq_map_sg(mq->queue, mq->req, mq->sg);
BUG_ON(!mq->bounce_sg);
sg_len = blk_rq_map_sg(mq->queue, mq->req, mq->bounce_sg);
mq->bounce_sg_len = sg_len;
/*
* Shortcut in the event we only get a single entry.
*/
if (sg_len == 1) {
memcpy(mq->sg, mq->bounce_sg, sizeof(struct scatterlist));
return 1;
}
mq->sg[0].page = virt_to_page(mq->bounce_buf);
mq->sg[0].offset = offset_in_page(mq->bounce_buf);
mq->sg[0].length = 0;
while (sg_len) {
mq->sg[0].length += mq->bounce_sg[sg_len - 1].length;
sg_len--;
}
return 1;
}
void mmc_queue_bounce_pre(struct mmc_queue *mq)
{
if (!mq->bounce_buf)
return;
if (mq->bounce_sg_len == 1)
return;
if (rq_data_dir(mq->req) != WRITE)
return;
copy_sg(mq->sg, 1, mq->bounce_sg, mq->bounce_sg_len);
}
void mmc_queue_bounce_post(struct mmc_queue *mq)
{
if (!mq->bounce_buf)
return;
if (mq->bounce_sg_len == 1)
return;
if (rq_data_dir(mq->req) != READ)
return;
copy_sg(mq->bounce_sg, mq->bounce_sg_len, mq->sg, 1);
}
......@@ -14,6 +14,9 @@ struct mmc_queue {
void *data;
struct request_queue *queue;
struct scatterlist *sg;
char *bounce_buf;
struct scatterlist *bounce_sg;
unsigned int bounce_sg_len;
};
extern int mmc_init_queue(struct mmc_queue *, struct mmc_card *, spinlock_t *);
......@@ -21,4 +24,8 @@ extern void mmc_cleanup_queue(struct mmc_queue *);
extern void mmc_queue_suspend(struct mmc_queue *);
extern void mmc_queue_resume(struct mmc_queue *);
extern unsigned int mmc_queue_map_sg(struct mmc_queue *);
extern void mmc_queue_bounce_pre(struct mmc_queue *);
extern void mmc_queue_bounce_post(struct mmc_queue *);
#endif
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