From 98ccf14909ba02a41c5925b0b2c92aeeef23d3b9 Mon Sep 17 00:00:00 2001
From: Pierre Ossman <drzeus@drzeus.cx>
Date: Sat, 12 May 2007 00:26:16 +0200
Subject: [PATCH] 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: Pierre Ossman <drzeus@drzeus.cx>
---
drivers/mmc/card/Kconfig | 18 ++++
drivers/mmc/card/block.c | 7 +-
drivers/mmc/card/queue.c | 191 ++++++++++++++++++++++++++++++++++++---
drivers/mmc/card/queue.h | 7 ++
4 files changed, 208 insertions(+), 15 deletions(-)
diff --git a/drivers/mmc/card/Kconfig b/drivers/mmc/card/Kconfig
index 9320a8c7323..a49cb9737cd 100644
--- a/drivers/mmc/card/Kconfig
+++ b/drivers/mmc/card/Kconfig
@@ -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.
+
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 540ff4bea54..cbd4b6e3e17 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -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);
diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index dd97bc79840..4fb2089dc69 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -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);
+}
+
diff --git a/drivers/mmc/card/queue.h b/drivers/mmc/card/queue.h
index 1590b3f3f1f..64e66e0d499 100644
--- a/drivers/mmc/card/queue.h
+++ b/drivers/mmc/card/queue.h
@@ -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
--
2.41.3