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| /rk3399_rockchip-uboot/drivers/mmc/ |
| H A D | sdhci.c | 7279e4870e5693d29cecb8ac10ba7588ff94f1a2 Mon May 15 06:07:24 UTC 2017 Ziyuan Xu <xzy.xu@rock-chips.com> mmc: sdhci: add the support for tuning
MMC framework has already implemented hs200 mode for eMMC devices,
moreover the standard SDHC3.0 controller support tuning. We can set the
corresponding flag in host->host_cpas.
Host driver issue tuning command repeatedly until the host controller
resets Execute Tuning to 0. Host controller resets Execute Tuning to 0
when tuning is completed or tuning is not completed within 40 times.
Host driver can abort this loop by 40 times CMD19/CMD21 issue or 150ms
time-out. If tuning is completed successfully, driver set Sampling Clock
Select to 1 and this means the host contorller start to use tuned
sampling clcok. If tuning is failed, host controller keeps Sampling
Clock Select to 0.
Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
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