linux_dsm_epyc7002/drivers/mmc
Nick Sanders 197160d52e 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>
2014-05-13 21:21:10 -04:00
..
card MMC highlights for 3.15: 2014-04-09 08:39:39 -07:00
core mmc: core: Improve support for deferred regulators 2014-05-12 18:08:24 -04:00
host mmc: sdhci: remove mdelay in eMMC tuning 2014-05-13 21:21:10 -04:00
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