Hi, On 02/25/2015 04:52 PM, Alim Akhtar wrote: > Hi Doug, > > > On Fri, Feb 20, 2015 at 5:19 AM, Doug Anderson <dianders@xxxxxxxxxxxx> wrote: >> Alim and Addy, >> >> On Sun, Feb 15, 2015 at 3:28 PM, Alim Akhtar <alim.akhtar@xxxxxxxxx> wrote: >>> Hi Addy, >>> >>> On Sat, Feb 14, 2015 at 11:47 AM, Addy Ke <addy.ke@xxxxxxxxxxxxxx> wrote: >>>> As show in mmc_power_up(), in MMC_POWER_UP state, the voltage isn't >>>> stable and we may get 'data busy' which can't be cleaned by resetting >>>> all blocks. So we should not send command to update clock in this state. >>>> >>>> Signed-off-by: Addy Ke <addy.ke@xxxxxxxxxxxxxx> >>>> --- >>>> drivers/mmc/host/dw_mmc.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c >>>> index 4d2e3c2..3472f9b 100644 >>>> --- a/drivers/mmc/host/dw_mmc.c >>>> +++ b/drivers/mmc/host/dw_mmc.c >>>> @@ -1102,7 +1102,8 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) >>>> drv_data->set_ios(slot->host, ios); >>>> >>>> /* Slot specific timing and width adjustment */ >>>> - dw_mci_setup_bus(slot, false); >>>> + if (ios->power_mode != MMC_POWER_UP) >>>> + dw_mci_setup_bus(slot, false); >>>> >>> This looks a HACK to me. >>> If stabilizing host voltage regulator is the problem, can you try out >>> below patch, and see if this resolve your issue? >> >> Actually, IMHO Alim's patch is more of a hack than Addy's. There's >> already a 10ms delay between "power up" and "power on" in the MMC core >> in mmc_power_up() state. That delay is commented as: >> > Well, my suggestion (adding 5ms in switch_volatge) was based on DW_MMC > databook (V2.41a) section "7.4.1.2 Voltage switch Normal Scenario" > step #7 which says:" After the 5ms timer expires, the host voltage > regulator is stable". if you want to stable power, How about using SDMMC_CMD_INIT flag? It waits for 80-clock before sending command.(To stable power) - You can refer to CMD register description. Best Regards, Jaehoon Chung > > PS: I have limited to no access of my mails and workstation until > March 9th, so replies will be slow. > >> /* >> * This delay should be sufficient to allow the power supply >> * to reach the minimum voltage. >> */ >> mmc_delay(10); >> >> That means that assuming that the voltage is stable in MMC_POWER_UP is >> not valid anyway. >> >> >> Addy's patch certainly needs more comments. In another context Olof suggested: >> >> /* >> * Skip bus setup while voltage is still stabilizing. Instead, >> * bus setup will be done at MMC_POWER_ON. >> */ >> >> >> ...thinking about this more, though: really the voltage should be >> stabilized when the regulator call returns (see my comments below). >> In actuality the "right" fix might be to just rearrange this function >> a little not to turn the clock on _before_ we even try to turn the >> voltage on. >> >> I've got that coded up but I'm still testing it... If you want to try >> it too, you can find it at >> <https://chromium-review.googlesource.com/251341>. >> >> Note that without my patch I find that I _really_ need Addy's patch to >> make sure that the card isn't busy in setup_bus. With my patch Addy's >> code catches the card busy less often. I'm still trying to see if >> there's a way to totally remove the need for his setup_bus and still >> trying to grok all the patches flying around... >> >> >>> =========== >>> [PATCH] mmc: dw_mmc: Wait for host voltage regulator to be stable >>> >>> Signed-off-by: Alim Akhtar <alim.akhtar@xxxxxxxxxxx> >>> --- >>> drivers/mmc/host/dw_mmc.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c >>> index 4d2e3c2..dc10fbb 100644 >>> --- a/drivers/mmc/host/dw_mmc.c >>> +++ b/drivers/mmc/host/dw_mmc.c >>> @@ -1202,6 +1202,9 @@ static int dw_mci_switch_voltage(struct mmc_host >>> *mmc, struct mmc_ios *ios) >>> } >>> mci_writel(host, UHS_REG, uhs); >>> >>> + /* wait for 5ms so that host voltage regulator is stable */ >>> + usleep_range(5000, 5500); >>> + >> >> Alim: if you have some other instance where you actually need VQMMC to >> stabilize it should probably be done in a different way. If I >> understand correctly it is the regulator core's job to make sure that >> voltage is stable before returning. If you have a gpio-regulator you >> may be able to use "startup-delay-us" to specify how long the >> regulator takes to come up. You could also look at >> 'regulator-enable-ramp-delay' >> >> -Doug > > > -- 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
