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mmc: sdhci: avoid walking SG list for writes

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If we are writing data to the card, there is no point in walking the
scatterlist to find out if there are any unaligned entries; this is a
needless waste of CPU cycles.  Avoid this by checking for a non-read
tranfer first.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Russell King 2016-01-26 13:40:06 +00:00 • committed by Ulf Hansson
commit 47fa961340
1 changed files with 22 additions and 20 deletions
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44
drivers/mmc/host/sdhci.c
View file

@ -559,37 +559,39 @@ static void sdhci_adma_table_post(struct sdhci_host *host,
void *align;
char *buffer;
unsigned long flags;
bool has_unaligned;
if (data->flags & MMC_DATA_READ)
direction = DMA_FROM_DEVICE;
else
direction = DMA_TO_DEVICE;
/* 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)
if (sg_dma_address(sg) & SDHCI_ADMA2_MASK) {
has_unaligned = true;
break;
}
if (data->flags & MMC_DATA_READ) {
bool has_unaligned = false;
if (has_unaligned && data->flags & MMC_DATA_READ) {
dma_sync_sg_for_cpu(mmc_dev(host->mmc), data->sg,
data->sg_len, direction);
align = host->align_buffer;
for_each_sg(data->sg, sg, host->sg_count, i) {
/* Do a quick scan of the SG list for any unaligned mappings */
for_each_sg(data->sg, sg, host->sg_count, i)
if (sg_dma_address(sg) & SDHCI_ADMA2_MASK) {
size = SDHCI_ADMA2_ALIGN -
(sg_dma_address(sg) & SDHCI_ADMA2_MASK);
has_unaligned = true;
break;
}
buffer = sdhci_kmap_atomic(sg, &flags);
memcpy(buffer, align, size);
sdhci_kunmap_atomic(buffer, &flags);
if (has_unaligned) {
dma_sync_sg_for_cpu(mmc_dev(host->mmc), data->sg,
data->sg_len, direction);
align += SDHCI_ADMA2_ALIGN;
align = host->align_buffer;
for_each_sg(data->sg, sg, host->sg_count, i) {
if (sg_dma_address(sg) & SDHCI_ADMA2_MASK) {
size = SDHCI_ADMA2_ALIGN -
(sg_dma_address(sg) & SDHCI_ADMA2_MASK);
buffer = sdhci_kmap_atomic(sg, &flags);
memcpy(buffer, align, size);
sdhci_kunmap_atomic(buffer, &flags);
align += SDHCI_ADMA2_ALIGN;
}
}
}
}