[linux-sunxi] [PATCH 3/3] mmc: sunxi: use controller automatic clock gating.
From: Hans de Goede <hidden>
Date: 2015-08-12 12:35:41
Also in:
linux-mmc, lkml
Hi, On 12-08-15 14:23, Michal Suchanek wrote:
When core does not set the MMC_QUIRK_BROKEN_CLK_GATING flag enable automatic hardware controlled clock gating on the mmc interface. Signed-off-by: Michal Suchanek <redacted>
In general this looks good, but I wonder how intensively this has been tested ? Also given the long latencies when using manual clock on/off support, have you done any testing to check what sort of latencies this adds, e.g. Both with and without the patch, dump all the filesystem caches: echo 3 > /proc/sys/vm/drop_caches And then do: time cat /some/small/file/on/the/sdcard Do this at least 3 time both with and without the patch, and see if there are any noticable differences ? Regards, Hans
quoted hunk ↗ jump to hunk
--- drivers/mmc/host/sunxi-mmc.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c index f808a02..443cab5 100644 --- a/drivers/mmc/host/sunxi-mmc.c +++ b/drivers/mmc/host/sunxi-mmc.c@@ -601,8 +601,13 @@ static int sunxi_mmc_oclk_onoff(struct sunxi_mmc_host *host, u32 oclk_en) rval = mmc_readl(host, REG_CLKCR); rval &= ~(SDXC_CARD_CLOCK_ON | SDXC_LOW_POWER_ON); - if (oclk_en) + if (oclk_en) { rval |= SDXC_CARD_CLOCK_ON; + if (!host->mmc->card || + !(host->mmc->card->quirks & MMC_QUIRK_BROKEN_CLK_GATING)) + + rval |= SDXC_LOW_POWER_ON; + } start = jiffies; end = start + msecs_to_jiffies(750);