On Wed, 2019-02-13 at 08:24 +0100, Ulf Hansson wrote: > On Wed, 13 Feb 2019 at 04:13, Chaotian Jing <chaotian.jing@xxxxxxxxxxxx> wrote: > > > > On Wed, 2019-02-13 at 08:54 +0800, Chaotian Jing wrote: > > > On Tue, 2019-02-12 at 10:04 +0200, Adrian Hunter wrote: > > > > On 12/02/19 4:04 AM, Chaotian Jing wrote: > > > > > On Tue, 2019-02-05 at 15:42 +0200, Adrian Hunter wrote: > > > > >> On 5/02/19 3:06 PM, Ulf Hansson wrote: > > > > >>> On Mon, 4 Feb 2019 at 14:42, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > > > > >>>> > > > > >>>> On 4/02/19 12:54 PM, Ulf Hansson wrote: > > > > >>>>> On Mon, 4 Feb 2019 at 10:58, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > > > > >>>>>> > > > > >>>>>> On 1/02/19 10:10 AM, Ulf Hansson wrote: > > > > >>>>>>> On Fri, 1 Feb 2019 at 02:38, Chaotian Jing <chaotian.jing@xxxxxxxxxxxx> wrote: > > > > >>>>>>>> > > > > >>>>>>>> On Thu, 2019-01-31 at 16:58 +0100, Ulf Hansson wrote: > > > > >>>>>>>>> On Thu, 31 Jan 2019 at 08:53, Chaotian Jing <chaotian.jing@xxxxxxxxxxxx> wrote: > > > > >>>>>>>>>> > > > > >>>>>>>>>> mmc_hs400_to_hs200() begins with the card and host in HS400 mode. > > > > >>>>>>>>>> Therefore, any commands sent to the card should use HS400 timing. > > > > >>>>>>>>>> It is incorrect to reduce frequency to 50Mhz before sending the switch > > > > >>>>>>>>>> command, in this case, only reduce clock frequency to 50Mhz but without > > > > >>>>>>>>>> host timming change, host is still in hs400 mode but clock changed from > > > > >>>>>>>>>> 200Mhz to 50Mhz, which makes the tuning result unsuitable and cause > > > > >>>>>>>>>> the switch command gets response CRC error. > > > > >>>>>>>>> > > > > >>>>>>>>> According the eMMC spec there is no violation by decreasing the clock > > > > >>>>>>>>> frequency like this. We can use whatever value <=200MHz. > > > > >>>>>>>>> > > > > >>>>>>>>> However, perhaps in practice this becomes an issue, due to the tuning > > > > >>>>>>>>> for HS400 has been done on the "current" frequency. > > > > >>>>>>>>> > > > > >>>>>>>>> As as start, I think you need to clarify this in the changelog. > > > > >>>>>>>>> > > > > >>>>>>>> Yes, reduce clock frequency to 50Mhz is no Spec violation, but it may > > > > >>>>>>>> cause __mmc_switch() gets response CRC error, decreasing the clock but > > > > >>>>>>>> without HOST mode change, on the host side, host driver do not know > > > > >>>>>>>> what's operation the core layer want to do and can only set current bus > > > > >>>>>>>> clock to 50Mhz, without tuning parameter change, it has a chance lead to > > > > >>>>>>>> response CRC error. even lower clock frequency, but with the wrong > > > > >>>>>>>> tuning parameter setting(the setting is of hs400 tuning @200Mhz). > > > > >>>>>>> > > > > >>>>>>> Right, makes sense. > > > > >>>>>>> > > > > >>>>>>>>>> > > > > >>>>>>>>>> this patch refers to mmc_select_hs400(), make the reduce clock frequency > > > > >>>>>>>>>> after card timing change. > > > > >>>>>>>>>> > > > > >>>>>>>>>> Signed-off-by: Chaotian Jing <chaotian.jing@xxxxxxxxxxxx> > > > > >>>>>>>>>> --- > > > > >>>>>>>>>> drivers/mmc/core/mmc.c | 8 ++++---- > > > > >>>>>>>>>> 1 file changed, 4 insertions(+), 4 deletions(-) > > > > >>>>>>>>>> > > > > >>>>>>>>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c > > > > >>>>>>>>>> index da892a5..21b811e 100644 > > > > >>>>>>>>>> --- a/drivers/mmc/core/mmc.c > > > > >>>>>>>>>> +++ b/drivers/mmc/core/mmc.c > > > > >>>>>>>>>> @@ -1239,10 +1239,6 @@ int mmc_hs400_to_hs200(struct mmc_card *card) > > > > >>>>>>>>>> int err; > > > > >>>>>>>>>> u8 val; > > > > >>>>>>>>>> > > > > >>>>>>>>>> - /* Reduce frequency to HS */ > > > > >>>>>>>>>> - max_dtr = card->ext_csd.hs_max_dtr; > > > > >>>>>>>>>> - mmc_set_clock(host, max_dtr); > > > > >>>>>>>>>> - > > > > >>>>>>>>> > > > > >>>>>>>>> As far as I can tell, the reason to why we change the clock frequency > > > > >>>>>>>>> *before* the call to __mmc_switch() below, is probably to try to be on > > > > >>>>>>>>> the safe side and conform to the spec. > > > > >>>>>>>>> > > > > >>>>>>>> Agree, it Must be more safe with lower clock frequency, but the > > > > >>>>>>>> precondition is to make the host side recognize current timing is not > > > > >>>>>>>> HS400 mode. it has no method to find a safe setting to ensure no > > > > >>>>>>>> response CRC error when reduce clock from 200Mhz to 50Mhz. > > > > >>>>>>>>> However, I think you have a point, as the call to __mmc_switch(), > > > > >>>>>>>>> passes the "send_status" parameter as false, no other command than the > > > > >>>>>>>>> CMD6 is sent to the card. > > > > >>>>>>>>> > > > > >>>>>>>> yes, the send status command was sent only after __mmc_switch() done. > > > > >>>>>>>>>> /* Switch HS400 to HS DDR */ > > > > >>>>>>>>>> val = EXT_CSD_TIMING_HS; > > > > >>>>>>>>>> err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING, > > > > >>>>>>>>>> @@ -1253,6 +1249,10 @@ int mmc_hs400_to_hs200(struct mmc_card *card) > > > > >>>>>>>>>> > > > > >>>>>>>>>> mmc_set_timing(host, MMC_TIMING_MMC_DDR52); > > > > >>>>>>>>>> > > > > >>>>>>>>>> + /* Reduce frequency to HS */ > > > > >>>>>>>>>> + max_dtr = card->ext_csd.hs_max_dtr; > > > > >>>>>>>>>> + mmc_set_clock(host, max_dtr); > > > > >>>>>>>>>> + > > > > >>>>>>>>> > > > > >>>>>>>>> Perhaps it's even more correct to change the clock frequency before > > > > >>>>>>>>> the call to mmc_set_timing(host, MMC_TIMING_MMC_DDR52). Otherwise you > > > > >>>>>>>>> will be using the DDR52 timing in the controller, but with a too high > > > > >>>>>>>>> frequency. > > > > >>>>>>>>> > > > > >>>>>>>> for Our host, it has no impact to change the clock before or after > > > > >>>>>>>> change timing, as the mmc_set_timing() is only for host side, not > > > > >>>>>>>> related to MMC card side and no commands sent do card before the > > > > >>>>>>>> timing/clock change completed. > > > > >>>>>>> > > > > >>>>>>> Alright. After a second thought, it actually looks more consistent > > > > >>>>>>> with mmc_select_hs400() to do it after, as what you propose in > > > > >>>>>>> $subject patch. > > > > >>>>>>> > > > > >>>>>>> So, let's keep it as is. > > > > >>>>>>> > > > > >>>>>>>>>> err = mmc_switch_status(card); > > > > >>>>>>>>>> if (err) > > > > >>>>>>>>>> goto out_err; > > > > >>>>>>>>>> -- > > > > >>>>>>>>>> 1.8.1.1.dirty > > > > >>>>>>>>>> > > > > >>>>>>>>> > > > > >>>>>>>>> Finally, it sounds like you are trying to fix a real problem, can you > > > > >>>>>>>>> please provide some more information what is happening when the > > > > >>>>>>>>> problem occurs at your side? > > > > >>>>>>>>> > > > > >>>>>>>> Yes, I got a problem with new kernel version. with > > > > >>>>>>>> commit:57da0c042f4af52614f4bd1a148155a299ae5cd8, this commit makes > > > > >>>>>>>> re-tuning every time when access RPMB partition. > > > > >>>>>>> > > > > >>>>>>> Okay, could you please add this as fixes tag for the next version of the patch. > > > > >>>>>>> > > > > > Ok, sorry for late reply due to Chinese New Year. > > > > >>>>>>>> > > > > >>>>>>>> in fact, our host tuning result of hs400 is very stable and almost never > > > > >>>>>>>> get response CRC error with clock frequency at 200Mhz. but cannot ensure > > > > >>>>>>>> this tuning result also suitable when running at HS400 mode @50Mhz. as I > > > > >>>>>>>> mentioned before, the host side does not know the reason of reduce clock > > > > >>>>>>>> frequency to 50Mhz at HS400 mode, so what's the host side can do is only > > > > >>>>>>>> reduce the bus clock to 50Mhz, even it can just only set the tuning > > > > >>>>>>>> setting to default when clock frequency lower than 50Mhz, but both card > > > > >>>>>>>> & host side are still at HS400 mode, still cannot ensure this setting is > > > > >>>>>>>> suitable. > > > > >>>>>>> > > > > >>>>>>> Right, thanks for clarifying. > > > > >>>>>>> > > > > >>>>>>> So I am expecting a new version with a fixes tag and some > > > > >>>>>>> clarification of the changelog, then I am ready to apply this to give > > > > >>>>>>> it some test. > > > > >>>>>> > > > > >>>>>> The switch from HS400 mode is done for tuning at times when CRC errors are a > > > > >>>>>> possibility e.g. after a CRC error during transfer. So if the frequency is > > > > >>>>>> not to be reduced, then some mitigation is needed for the possibility that > > > > >>>>>> the CMD6 response itself will have a CRC error. > > > > >>>>> > > > > >>>>> That's a good point! > > > > >>>>> > > > > >>>>> However, how can we know that a CMD6 command is successfully > > > > >>>>> completed, if there is CRC errors detected during the transmission? I > > > > >>>>> guess we can't!? > > > > >>>> > > > > >>>> Yes, in that case, the only option is to assume the CMD6 was successful, > > > > >>>> like in > > > > >>>> > > > > >>>> commit ef3d232245ab7a1bf361c52449e612e4c8b7c5ab > > > > >>>> Author: Adrian Hunter <adrian.hunter@xxxxxxxxx> > > > > >>>> Date: Fri Dec 2 13:16:35 2016 +0200 > > > > >>>> > > > > >>>> mmc: mmc: Relax checking for switch errors after HS200 switch > > > > >>> > > > > >>> Well, relaxing the check for switch errors, is to me a different > > > > >>> thing. This means we are first doing the CMD6, then allowing the > > > > >>> following status command (CMD13) to have CRC errors. Actually, even > > > > >>> the spec mention this as a case to consider. I guess it's because the > > > > >>> card internally have switched to a new speed mode timing. > > > > >>> > > > > >>> Allowing CRC errors for the actual CMD6 sound more fragile to me. Of > > > > >>> course, we can always try and see what happens. > > > > >>> > > > > >>> Chaotian, can you give it a go? Somehow, change the call to > > > > >>> __mmc_switch() in mmc_hs400_to_hs200(), so the CMD6 doesn't have the > > > > >>> CRC flag set. > > @Adrian, @Ulf, another question: if remove the MMC_RSP_CRC flag, it will > > have big impact to all host driver, as the "mmc_resp_type()" can not get > > MMC_RESP_R1B return value, so many host drivers use mmc_resp_type() to > > get resp type. if We make CMD6 does not have CRC flag set, then We must > > modify the using of "mmc_resp_type()" to "mmc_resp_type() | MMC_RSP_CRC" > > in all host drives. the same issue occurs at other place which remove > > MMC_RSP_CRC(eg. mmc_cqe_recovery()). > > The idea is actually to try to change this for all host drivers, of > course it's only for this particular CMD6 in question, so not for all > CMD6. > Well, I mean, all commands(R1/R1B/R5/R6/R7) with MMC_RSP_CRC flag NOT set will cause host driver cannot work properly, host driver cannot get correct response type by mmc_resp_type() to padding its register. if the MMC core layer supports "cmd.flags &= ~MMC_RSP_CRC", then must modify all host driver to support it. So, in this case, the easy way to check return value of this __mmc_switch() may like blow: if (err && err != -EILSEQ) > However, before we consider doing such a change, we need to know if it > solves the problem for you? If it doesn't, then we can drop the idea. > > As a perhaps better alternative, Adrian also suggested, if possible, > to let the mediatek driver change to "fixed sampling mode" via the > ->set_ios() host ops, at the point when the clk rate drops to > HS-frequency, but still running with MMC_TIMING_MMC_HS400 timings. Of > course this means "fixed sampling" needs to be supported by the > mediatek IP. > > If neither of this works for you, we need to consider something else. > > [...] > > Kind regards > Uffe
