On 14 December 2017 at 20:04, Zhoujie Wu <zjwu@xxxxxxxxxxx> wrote: > Hi Ulf, > > On 12/14/2017 12:41 AM, Ulf Hansson wrote: >> >> External Email >> >> ---------------------------------------------------------------------- >> On 14 December 2017 at 00:48, Zhoujie Wu <zjwu@xxxxxxxxxxx> wrote: >>> >>> According to SD spec 3.00 3.6.1 signal voltage switch >>> procedure, 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. >>> >> The core already deals with this. See mmc_set_uhs_voltage() and >> mmc_host_set_uhs_voltage(). >> >> We even have a retry mechanism in place. > > I checked these functions, they just make sure when do signal voltage > switch, gate the clock to SD card 5ms and wait 1ms before check data lines. > This patch is following below spec requirement when switching signal voltage > to 1.8V, wait 5ms after set 1.8V signal Enable bit in Host control 2 > register. Right, so this is an SDHCI controller requirement. Could you perhaps clarify that in the changlog, then I am happy. > Current code will set 1.8V Signal Enable bit and check if this bit is > cleared by host right after that, the bit is not cleared and host report > "1.8V regulator output did not became stable". > > You can find the steps at SD spec 3.0 3.6.1. > (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). >> >> >>> On some cards, found without the delay would see "1.8V >>> regulator output did not became stable" err log. >> >> Seems like you need to fix the regulator instead. >> >> BTW, is this a regression? No? > > It is not regulator related, the regulator already output 1.8V and add delay > after regulator set voltage didn't help. > The only solution is to add 5ms after set 1.8V signal enable bit . > Not a regression issue, we recently found it when enabling uhs on some > platforms since they didn't enable it previously. I see, thanks for clarifying. Kind regards Uffe -- 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
