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| author | Nick Sanders | 2014-05-07 03:52:38 +0200 |
|---|---|---|
| committer | Chris Ball | 2014-05-14 03:21:10 +0200 |
| commit | 197160d52e859575ff0ad1afd674ab2a825b9f83 (patch) | |
| tree | 949e5e32cfefa9e253c2efe80349925d3e083616 /drivers | |
| parent | MAINTAINERS: mmc: Update email for host driver maintainer (diff) | |
| download | kernel-qcow2-linux-197160d52e859575ff0ad1afd674ab2a825b9f83.tar.gz kernel-qcow2-linux-197160d52e859575ff0ad1afd674ab2a825b9f83.tar.xz kernel-qcow2-linux-197160d52e859575ff0ad1afd674ab2a825b9f83.zip | |
mmc: sdhci: remove mdelay in eMMC tuning
This patch removes an unneccesary 1ms mdelay in the HS200 tuning
loop, called 40 times per retuning. Currently this causes a latency
of >40ms on any emmc accesses triggering wake from runtime PM,
which can occur for a significant portion of reads on a mostly idle system.
The delay is left in place for SD Cards, which use
MMC_SEND_TUNING_BLOCK rather than MMC_SEND_TUNING_BLOCK_HS200.
I'm not able to find evidence that this is required for SD in the
specs I have access to, however this delay has been present from
initial checkin for SD so I have preserved the original behavior for
compatibility.
This has been verified to fix observed glitching on local audio
playback and recording on apps with inbuilt assumptions on storage
latency.
Signed-off-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/mmc/host/sdhci.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index a31f06dadf6f..255aaf18db35 100644 --- a/drivers/mmc/host/sdhci.c +++ b/drivers/mmc/host/sdhci.c @@ -1994,7 +1994,10 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode) ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2); tuning_loop_counter--; timeout--; - mdelay(1); + + /* eMMC spec does not require a delay between tuning cycles */ + if (opcode == MMC_SEND_TUNING_BLOCK) + mdelay(1); } while (ctrl & SDHCI_CTRL_EXEC_TUNING); /* |