On 15/12/17 21:28, Zhoujie Wu wrote: > According to SD spec 3.00 3.6.1 signal voltage switch > procedure step 6~8, > (6) Set 1.8V Signal Enable in the Host Control 2 register. > (7) Wait 5ms. 1.8V voltage regulator shall be stable within this period. > (8) If 1.8V Signal Enable is cleared by Host Controller, go to step (12). > > Host should wait 5ms after set 1.8V signal enable bit in > Host Control 2 register and check if 1.8V is stable or not. > > But current code checks if this bit is cleared by controller > right after set it. On some platforms found the bit is not > cleared right away and host reports "1.8V regulator output > did not became stable" and 5ms delay can help. The check is for the bit set not cleared. > > Follow the spec and add 5ms delay to make sure the 1.8V Signal Enable > bit is cleared. > > Signed-off-by: Zhoujie Wu <zjwu@xxxxxxxxxxx> > --- > drivers/mmc/host/sdhci.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c > index e9290a3..fe5f208 100644 > --- a/drivers/mmc/host/sdhci.c > +++ b/drivers/mmc/host/sdhci.c > @@ -1933,6 +1933,9 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc, > if (host->ops->voltage_switch) > host->ops->voltage_switch(host); > > + /* Wait for 5ms */ > + usleep_range(5000, 5500); We have managed without this delay for a while and I am reluctant to add delays that might anyway be specific to the controller. What do you think about implementing ->voltage_switch() and putting the delay there? > + > /* 1.8V regulator output should be stable within 5 ms */ > ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2); > if (ctrl & SDHCI_CTRL_VDD_180) > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
