This is a note to let you know that I've just added the patch titled
mmc: sdhci: avoid unnecessary mapping/unmapping of align buffer
to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mmc-sdhci-avoid-unnecessary-mapping-unmapping-of-align-buffer.patch
and it can be found in the queue-4.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From edd63fcc97cdb53279a7c43fa1691f5913d92793 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Date: Tue, 26 Jan 2016 13:39:50 +0000
Subject: mmc: sdhci: avoid unnecessary mapping/unmapping of align buffer
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
commit edd63fcc97cdb53279a7c43fa1691f5913d92793 upstream.
Unnecessarily mapping and unmapping the align buffer for SD cards is
expensive: performance measurements on iMX6 show that this gives a hit
of 10% on hdparm buffered disk reads.
MMC/SD card IO comes from the mm/vfs which gives us page based IO, so
for this case, the align buffer is not going to be used. However, we
still map and unmap this buffer.
Eliminate this by switching the align buffer to be a DMA coherent
buffer, which needs no DMA maintenance to access the buffer.
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Tested-by: Gregory CLEMENT <gregory.clement@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/mmc/host/sdhci.c | 54 +++++++++++++++--------------------------------
1 file changed, 18 insertions(+), 36 deletions(-)
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -465,8 +465,6 @@ static void sdhci_adma_mark_end(void *de
static int sdhci_adma_table_pre(struct sdhci_host *host,
struct mmc_data *data)
{
- int direction;
-
void *desc;
void *align;
dma_addr_t addr;
@@ -483,20 +481,9 @@ static int sdhci_adma_table_pre(struct s
* We currently guess that it is LE.
*/
- if (data->flags & MMC_DATA_READ)
- direction = DMA_FROM_DEVICE;
- else
- direction = DMA_TO_DEVICE;
-
- host->align_addr = dma_map_single(mmc_dev(host->mmc),
- host->align_buffer, host->align_buffer_sz, direction);
- if (dma_mapping_error(mmc_dev(host->mmc), host->align_addr))
- goto fail;
- BUG_ON(host->align_addr & SDHCI_ADMA2_MASK);
-
host->sg_count = sdhci_pre_dma_transfer(host, data);
if (host->sg_count < 0)
- goto unmap_align;
+ return -EINVAL;
desc = host->adma_table;
align = host->align_buffer;
@@ -570,22 +557,7 @@ static int sdhci_adma_table_pre(struct s
/* nop, end, valid */
sdhci_adma_write_desc(host, desc, 0, 0, ADMA2_NOP_END_VALID);
}
-
- /*
- * Resync align buffer as we might have changed it.
- */
- if (data->flags & MMC_DATA_WRITE) {
- dma_sync_single_for_device(mmc_dev(host->mmc),
- host->align_addr, host->align_buffer_sz, direction);
- }
-
return 0;
-
-unmap_align:
- dma_unmap_single(mmc_dev(host->mmc), host->align_addr,
- host->align_buffer_sz, direction);
-fail:
- return -EINVAL;
}
static void sdhci_adma_table_post(struct sdhci_host *host,
@@ -605,9 +577,6 @@ static void sdhci_adma_table_post(struct
else
direction = DMA_TO_DEVICE;
- dma_unmap_single(mmc_dev(host->mmc), host->align_addr,
- host->align_buffer_sz, direction);
-
/* Do a quick scan of the SG list for any unaligned mappings */
has_unaligned = false;
for_each_sg(data->sg, sg, host->sg_count, i)
@@ -2984,14 +2953,21 @@ int sdhci_add_host(struct sdhci_host *ho
&host->adma_addr,
GFP_KERNEL);
host->align_buffer_sz = SDHCI_MAX_SEGS * SDHCI_ADMA2_ALIGN;
- host->align_buffer = kmalloc(host->align_buffer_sz, GFP_KERNEL);
+ host->align_buffer = dma_alloc_coherent(mmc_dev(mmc),
+ host->align_buffer_sz,
+ &host->align_addr,
+ GFP_KERNEL);
if (!host->adma_table || !host->align_buffer) {
if (host->adma_table)
dma_free_coherent(mmc_dev(mmc),
host->adma_table_sz,
host->adma_table,
host->adma_addr);
- kfree(host->align_buffer);
+ if (host->align_buffer)
+ dma_free_coherent(mmc_dev(mmc),
+ host->align_buffer_sz,
+ host->align_buffer,
+ host->align_addr);
pr_warn("%s: Unable to allocate ADMA buffers - falling back to standard DMA\n",
mmc_hostname(mmc));
host->flags &= ~SDHCI_USE_ADMA;
@@ -3003,10 +2979,14 @@ int sdhci_add_host(struct sdhci_host *ho
host->flags &= ~SDHCI_USE_ADMA;
dma_free_coherent(mmc_dev(mmc), host->adma_table_sz,
host->adma_table, host->adma_addr);
- kfree(host->align_buffer);
+ dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz,
+ host->align_buffer, host->align_addr);
host->adma_table = NULL;
host->align_buffer = NULL;
}
+
+ /* dma_alloc_coherent returns page aligned and sized buffers */
+ BUG_ON(host->align_addr & SDHCI_ADMA2_MASK);
}
/*
@@ -3469,7 +3449,9 @@ void sdhci_remove_host(struct sdhci_host
if (host->adma_table)
dma_free_coherent(mmc_dev(mmc), host->adma_table_sz,
host->adma_table, host->adma_addr);
- kfree(host->align_buffer);
+ if (host->align_buffer)
+ dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz,
+ host->align_buffer, host->align_addr);
host->adma_table = NULL;
host->align_buffer = NULL;
Patches currently in stable-queue which might be from rmk+kernel@xxxxxxxxxxxxxxxx are
queue-4.5/mmc-sdhci-fix-command-response-crc-error-handling.patch
queue-4.5/mmc-sdhci-avoid-unnecessary-mapping-unmapping-of-align-buffer.patch
queue-4.5/mmc-sdhci-move-initialisation-of-command-error-member.patch
queue-4.5/mmc-sdhci-fix-data-timeout-part-2.patch
queue-4.5/mmc-sdhci-clean-up-command-error-handling.patch
queue-4.5/mmc-sdhci-further-fix-for-dma-unmapping-in-sdhci_post_req.patch
queue-4.5/mmc-sdhci-pxav3-fix-higher-speed-mode-capabilities.patch
queue-4.5/mmc-sdhci-fix-data-timeout-part-1.patch
queue-4.5/mmc-sdhci-plug-dma-mapping-leak-on-error.patch
--
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