RE: Issue with non-UHS-I SD3.0 cards

["Subhash Jadavani" <subhashj@codeaurora.org>]

Hi Arindam,

> -----Original Message-----
> From: linux-mmc-owner@vger.kernel.org [mailto:linux-mmc-
> owner@vger.kernel.org] On Behalf Of Nath, Arindam
> Sent: Saturday, August 06, 2011 12:27 AM
> To: Subhash Jadavani; linux-mmc@vger.kernel.org
> Cc: 'Chris Ball'; 'Philip Rakity'; 'zhangfei gao'
> Subject: RE: Issue with non-UHS-I SD3.0 cards
> 
> 
> 
> > -----Original Message-----
> > From: Nath, Arindam
> > Sent: Saturday, August 06, 2011 12:15 AM
> > To: 'Subhash Jadavani'; linux-mmc@vger.kernel.org
> > Cc: 'Chris Ball'; 'Philip Rakity'; 'zhangfei gao'
> > Subject: RE: Issue with non-UHS-I SD3.0 cards
> >
> > Hi Subhash,
> >
> >
> > > -----Original Message-----
> > > From: Subhash Jadavani [mailto:subhashj@codeaurora.org]
> > > Sent: Friday, August 05, 2011 7:01 PM
> > > To: linux-mmc@vger.kernel.org
> > > Cc: Nath, Arindam; 'Chris Ball'; 'Philip Rakity'; 'zhangfei gao'
> > > Subject: Issue with non-UHS-I SD3.0 cards
> > >
> > > Hi,
> > >
> > > I am seeing the issue where "SanDisk Extreme SDHC 8GB Class 10
> card"
> > is
> > > running in "Default Speed" mode even though it supports "High
> Speed"
> > > mode.
> > > After analysis, I found that this card is advertising itself as
> SD3.0
> > > card
> > > (with SD_SPEC=2 and SD_SPEC3=1 in SCR). But current mmc core later
> > > initialization sequence for SD3.0 cards is such that these non-UHS-
> I
> > > SD3.0
> > > cards runs in Default Speed mode @25MHz.
> > >
> > > Here is Essential conditions to indicate Version 3.00 Card (from
> > SD3.01
> > > spec)
> > >     (SD_SPEC=2 and SD_SPEC3=1) :
> > >     (1) The card shall support CMD6
> > >     (2) The card shall support CMD8
> > >     (3) The card shall support CMD42
> > >     (4) User area capacity shall be up to 2GB (SDSC) or 32GB (SDHC)
> > >         User area capacity shall be more than or equal to 32GB and
> > >         up to 2TB (SDXC)
> > >     (5) Speed Class shall be supported (SDHC or SDXC)
> >
> > I went through the particular section of the spec again, and IMO, the
> > essential conditions are for the manufacturer of the card to
> advertise
> > his card as SD3.0 card or otherwise. From software point of view, the
> > SD_SPEC=2 _and_ SD_SPEC3=1 will indicate a SD3.0 card.
> 
> I misread your comment, so please ignore what you mentioned above. So
> if I understand correctly, in your case *sd_spec3* is set for the card,
> even though it is a non UHS-I card. In that case, what you tried in
> your patch looks fine, except that I would suggest to move it inside
> the
> 
> if (card->scr.sda_spec3) {
> 	...
> }
> 
> condition.
> 

You mean moving the " card->sw_caps.hs_max_dtr = 50000000;" under if
(card->scr.sda_spec3) condition and still retaining the else condition for "
if (card->scr.sda_spec3) ".

Something like this:

if (card->scr.sda_spec3) {
       if (status[13] & 0x02)
               card->sw_caps.hs_max_dtr = 50000000;
	...
	...
	
} else {
       if (status[13] & 0x02)
               card->sw_caps.hs_max_dtr = 50000000;
}

I thought it's duplication of code as both if & else condition is executing
the same code so thought of putting it outside of if, else. 
I am even ok with putting it inside "if (card->scr.sda_spec3)", if you think
it's better.

Regards,
Subhash


> >
> > Thanks,
> > Arindam
> >
> > >
> > >
> > > So even if SD card doesn't support any of the newly defined UHS-I
> bus
> > > speed
> > > mode, it can advertise itself as SD3.0 cards as long as it supports
> > all
> > > the
> > > essential conditions of SD3.0 cards. Given this, these type of
> cards
> > > should
> > > at least run in High Speed mode @50MHZ if it supports HS.
> > >
> > > Here are the changes you have to do to make non-UHS-I SD3.0 cards
> run
> > > in
> > > High Speed Mode @50MHz. Do let me know if looks fine or not, so I
> can
> > > post
> > > the formal patch.
> > >
> > > ---
> > >  drivers/mmc/core/sd.c |    6 +++---
> > >  1 files changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> > > index 907662a..3fab676 100644
> > > --- a/drivers/mmc/core/sd.c
> > > +++ b/drivers/mmc/core/sd.c
> > > @@ -305,6 +305,9 @@ static int mmc_read_switch(struct mmc_card
> *card)
> > >                 goto out;
> > >         }
> > >
> > > +       if (status[13] & 0x02)
> > > +               card->sw_caps.hs_max_dtr = 50000000;
> > > +
> > >         if (card->scr.sda_spec3) {
> > >                 card->sw_caps.sd3_bus_mode = status[13];
> > >
> > > @@ -347,9 +350,6 @@ static int mmc_read_switch(struct mmc_card
> *card)
> > >                 }
> > >
> > >                 card->sw_caps.sd3_curr_limit = status[7];
> > > -       } else {
> > > -               if (status[13] & 0x02)
> > > -                       card->sw_caps.hs_max_dtr = 50000000;
> > >         }
> > >
> > >  out:
> > > --
> > >
> > >
> > > Regards,
> > > Subhash
> > >
> > >
> 
> 
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