Re: [PATCH] mmc: enable UHS voltage switch for SDSC if supported【请注意，邮件由linux-mmc-owner@xxxxxxxxxxxxxxx代发】

[Shawn Lin]

On 2021/4/23 14:38, Christian Löhle wrote:
> Claiming UHS-I support with SDSC is pretty rare, for obvious reasons (namely they are non-standard, so it's a gamble if a host makes use of it), but here you go:
> https://de.rs-online.com/web/p/micro-sd-karten/8743910/
> (sorry for the german, the site has a en. subpage, but it's certificate seem untrusted.)
> The more likely case is that they do not advertise UHS-I to customers,
> but the card will show support to the host.
> Let's look at this product, just as an example.
> https://www.tme.eu/html/EN/goodram-industrial-industrial-sd-sd-micro-memory-cards/ramka_15242_EN_pelny.html
> They provide an MLC and pSLC version of each device, with half the capacity naturally.
> The 4GB MLC claims UHS-I support, the 2GB pSLC is very likely to be the same controller,
> it only claims Class 6.
> So either they specifically changed the firmware to remove any UHS support indication,
> or, more likely IMO, the card still reports UHS support to the host.
> Such a card would benefit from this patch.
>
> Disclaimer: I do not own the product and have not confirmed this device in any way,
> but I have seen UHS support on other devices that do not advertise it for their
> SDSC versions.
> If the mailing list would be interested, I can try to acquire such devices, listed in
> public open stores. Modern, potentially UHS supporting cards. are,
> as mentioned in the initial Mail, often SLC or pSLC and often are made on
> a customers request.

Thanks for sharing these, but from the datasheets, these SDSC cards
claims their throught up to 20MB/s. So, I guess highpseed mode is enough
for them? what do you think?

> From: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
> Sent: Friday, April 23, 2021 3:34 AM
> To: Christian Löhle <CLoehle@xxxxxxxxxxxxxx>
> Cc: shawn.lin@xxxxxxxxxxxxxx <shawn.lin@xxxxxxxxxxxxxx>; pali@xxxxxxxxxx <pali@xxxxxxxxxx>; huyue2@xxxxxxxxxx <huyue2@xxxxxxxxxx>; tiantao6@xxxxxxxxxxxxx <tiantao6@xxxxxxxxxxxxx>; linux-mmc@xxxxxxxxxxxxxxx <linux-mmc@xxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>; ulf.hansson@xxxxxxxxxx <ulf.hansson@xxxxxxxxxx>
> Subject: Re: [PATCH] mmc: enable UHS voltage switch for SDSC if supported【请注意，邮件由linux-mmc-owner@xxxxxxxxxxxxxxx代发】
>   
> On 2021/4/22 21:18, Christian Löhle 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.
> > Especially for pSLCs in practice such cards benefit greatly by this patch,
>
> Cduld you provide some more infomation about the SDSC cards which ones
> are labeled as UHS, e.g brand, webpage....
>
> > as they can be new and UHS supporting, but must not lie about their CCS.
> > 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.
> >
> > 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--;
>
>
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