On Thu, 6 May 2021 at 10:34, Christian Löhle <CLoehle@xxxxxxxxxxxxxx> wrote: > > Well I am definitely for keeping this bug as a feature > and utilizing UHS with this patch ;) > I have tried all SDSC cards I could get my hands on and > have not seen any 'accidentally' reporting UHS support. That sounds promising. > > I tested the patch with own custom cards. > (Hyperstone, my employer, develops controllers for flash > storage.) I see, thanks for sharing! > > There you would have to make the same choice, disabling > UHS support reporting for all SDSC cards, but as some > hosts accept UHS (including voltage switch) without checking > CCS, this would throttle performance. > (One such host is e.g. > 8564:4000 Transcend Information, Inc. microSD/SD/CF UHS-II Card Reader) > > It would be nice to have this in linux-mmc as arguably the most > important SD native host. > I'm sure the other manufacturers either do not disable UHS > support for SDSC cards, or have at least been playing with the idea. Assuming I don't find any issues when I am testing some of my older SD cards, I am definitely open to change into what you propose in $subject patch. Although, I think it's important that we also state in the code with a comment somewhere - that we deliberately have decided to deviate from the SD spec for the reasons you have pointed out in our discussions. Can you perhaps prepare and post a new version and possibly also work a little bit on the commit message to make things a bit more clear? In the meantime, I will test some SD cards at my side... Kind regards Uffe > > Regards, > Christian > > From: Ulf Hansson <ulf.hansson@xxxxxxxxxx> > Sent: Wednesday, May 5, 2021 4:20 PM > To: Christian Löhle <CLoehle@xxxxxxxxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>; linux-mmc@xxxxxxxxxxxxxxx <linux-mmc@xxxxxxxxxxxxxxx>; pali@xxxxxxxxxx <pali@xxxxxxxxxx>; huyue2@xxxxxxxxxx <huyue2@xxxxxxxxxx>; tiantao6@xxxxxxxxxxxxx <tiantao6@xxxxxxxxxxxxx> > Subject: Re: [PATCH] mmc: enable UHS voltage switch for SDSC if supported > > On Wed, 5 May 2021 at 14:13, Christian Löhle <CLoehle@xxxxxxxxxxxxxx> wrote: > > > > So two cards that advertise UHS: > > https://www.euric.de/de/flash-speicher/sd-microsd/sd/ > > Model SDI790 > > and > > https://na.industrial.panasonic.com/products/storage-media/industrial-sd-cards/lineup/industrial-grade-2d-nand/series/71695 > > Thanks for the links! > > Are these the ones that you have been using for testing? > > > Hopefully that suffices as a couple, otherwise I would buy some > > that do not advertise it and actually check if they support it anyway. > > But 2GB SLC listings are kind of rare these days, so it's not as > > easy to find many that are still sold and available. > > Right. I have a whole bunch of old SD cards that I can test. I will > let you know when I have got some time to test some of them. > > The main worry (but I may be wrong) I have with the patch is that it > could cause problems for other older SDSC cards, which happens to > incorrectly set the S18A bit. I mean, before UHS-I was introduced in > the SD spec, this bit was just being reserved and potentially it could > have *any* value by the card manufacturer. As I said, let me do some > tests of my older SD cards. > > > > > My point about deviating from the standard was that these cards > > are already initialized as UHS, they just don't do the voltage switch. > > So anything reserved for UHS-I (e.g. CMD23 )is already being done > > by the host with the current linux-mmc, > > so the standard deviation is already there. > > Just the voltage switch is missing. > > Ah, yes you are right! > > We call mmc_sd_init_uhs_card() no matter whether the CCS bit is set. > Certainly this is a bug. Both the card and host aren't designed to > work under these conditions/timings. > > > > > Regards, > > Christian > > > > Kind regards > Uffe > > > > > From: Ulf Hansson <ulf.hansson@xxxxxxxxxx> > > Sent: Wednesday, May 5, 2021 12:09 PM > > To: Christian Löhle <CLoehle@xxxxxxxxxxxxxx> > > Subject: Re: [PATCH] mmc: enable UHS voltage switch for SDSC if supported > > > > On Thu, 22 Apr 2021 at 15:18, Christian Löhle <CLoehle@xxxxxxxxxxxxxx> wrote: > > > > > > Ignore the reported capacity if the card otherwise reports UHS support. > > > > > > Currently SDSC cards reporting UHS support except for the CCS do not run > > > through the voltage switch. > > > While strictly speaking a SDSC card cannot support UHS in compliance > > > with the standard, there is no good reason to throttle them that way. > > > > Maybe not, but I think the code just tries to conform to the SD spec. > > > > > Especially for pSLCs in practice such cards benefit greatly by this patch, > > > as they can be new and UHS supporting, but must not lie about their CCS. > > > > Can you provide some concrete examples of SDSC cards that support UHS-I? > > > > > The behaviour of linux-mmc for SDSC is deviating from the standard anyway > > > in such a case, as the card is treated as UHS card not supporting the > > > voltage switch in general. > > > Such a card will come up as > > > mmc0: new ultra high speed SDR25 SD card at address 0001. > > > Thus the subsystem will support CMD23 and others to the card. > > > But if we deviate from the standard anyway, then we might as well > > > not throttle SDSC to 25MB/s. > > > > Not sure I understand this correctly? Can you elaborate a bit more, so > > I understand how we deviate from the SD spec here? > > > > As far as I understand the spec, SDSC cards shouldn't support UHS-I. > > If we decide to deviate from the spec to support this anyway, at least > > we need to know about a couple of cards that actually supports this. > > > > Kind regards > > Uffe > > > > > > > > Signed-off-by: Christian Loehle <cloehle@xxxxxxxxxxxxxx> > > > --- > > > drivers/mmc/core/sd.c | 7 +++---- > > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c > > > index 6fa51a6ed058..281ca2da8e0b 100644 > > > --- a/drivers/mmc/core/sd.c > > > +++ b/drivers/mmc/core/sd.c > > > @@ -841,11 +841,10 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr) > > > return err; > > > > > > /* > > > - * In case CCS and S18A in the response is set, start Signal Voltage > > > - * Switch procedure. SPI mode doesn't support CMD11. > > > + * In case S18A in the response is set, start Signal Voltage Switch > > > + * procedure. SPI mode doesn't support CMD11. > > > */ > > > - if (!mmc_host_is_spi(host) && rocr && > > > - ((*rocr & 0x41000000) == 0x41000000)) { > > > + if (!mmc_host_is_spi(host) && rocr && (*rocr & 0x01000000)) { > > > err = mmc_set_uhs_voltage(host, pocr); > > > if (err == -EAGAIN) { > > > retries--; > > > -- > > > 2.31.1 > > > > > > Hyperstone GmbH | Line-Eid-Strasse 3 | 78467 Konstanz > > > Managing Directors: Dr. Jan Peter Berns. > > > Commercial register of local courts: Freiburg HRB381782 > > > > > > > Hyperstone GmbH | Line-Eid-Strasse 3 | 78467 Konstanz > > Managing Directors: Dr. Jan Peter Berns. > > Commercial register of local courts: Freiburg HRB381782 > > > > Hyperstone GmbH | Line-Eid-Strasse 3 | 78467 Konstanz > Managing Directors: Dr. Jan Peter Berns. > Commercial register of local courts: Freiburg HRB381782 >
