mmc: sdhci: Use Auto CMD Auto Select only when v4_mode is true
sdhci-of-dwcmshc meets an eMMC read performance regression with below command after commit 427b6514 ("mmc: sdhci: Add Auto CMD Auto Select support"): dd if=/dev/mmcblk0 of=/dev/null bs=8192 count=100000 Before the commit, the above command gives 120MB/s After the commit, the above command gives 51.3 MB/s So it looks like sdhci-of-dwcmshc expects Version 4 Mode for Auto CMD Auto Select. Fix the performance degradation by ensuring v4_mode is true to use Auto CMD Auto Select. Fixes: 427b6514 ("mmc: sdhci: Add Auto CMD Auto Select support") Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com> Acked-by: Adrian Hunter <adrian.hunter@intel.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201015174115.4cf2c19a@xhacker.debian Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Please register or sign in to comment