RE: power class selection fails on 3.5-rc1

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

> > Just for experiment, can we hack the value set to POWER_CLASS field to
> > 0x7 instead of 0x3? If this doesn't work, you may try other values
> > (starting from 1 till 15) to see setting any of the non-zero value
succeeds or
> not.
> 
> I tried 1 to 10 (as this is a 4.41 card) and none of them worked
(including 7).

Oh, that's not good.

Girish / Saugata,
Do you have any comments on this? Can you please comment on what type of
testing was done when we had initially added this power class selection?

Regards,
Subhash

> -----Original Message-----
> From: linux-mmc-owner@vger.kernel.org [mailto:linux-mmc-
> owner@vger.kernel.org] On Behalf Of Marc Dietrich
> Sent: Thursday, June 07, 2012 3:05 PM
> To: Subhash Jadavani
> Cc: 'Ulf Hansson'; Girish K S; saugata.das@linaro.org; linux-
> mmc@vger.kernel.org
> Subject: Re: power class selection fails on 3.5-rc1
> 
> On Wednesday 06 June 2012 15:14:48 Subhash Jadavani wrote:
> > > On 06/04/2012 06:35 PM, Marc Dietrich wrote:
> > > > Hi,
> > > >
> > > > somehow I hope this would go away by itself, but it didn't :-( I
> > > > reported this problem some time ago (see:
> > > > http://www.mail-archive.com/linux-
> > > > mmc@vger.kernel.org/msg13688.html ) but got no clear answer or fix.
> > > >
> > > > In addition to the information I posted on the thread above, I
> > > > also dumped the contents of the ext_csd register file (where reg
> > > > values are not zero):
> > > >
> > > > reg       Sandisk         Toshiba
> > > > 241     10      0x0a    50      0x32
> > > > 239     0       0x00    51      0x33
> > > > 238     0       0x00    119     0x77
> > > > 234     0       0x00    30      0x1e
> > > > 232     1       0x01    4       0x04
> > > > 231     21      0x15    21      0x15
> > > > 230     150     0x96    16      0x10
> > > > 229     150     0x96    66      0x42
> > > > 228     1       0x01    7       0x07
> > > > 226     8       0x08    16      0x10
> > > > 225     6       0x06    7       0x07
> > > > 224     4       0x04    8       0x08
> > > > 223     1       0x01    2       0x02
> > > > 222     8       0x08    16      0x10
> > > > 221     16      0x10    1       0x01
> > > > 220     8       0x08    7       0x07
> > > > 219     7       0x07    7       0x07
> > > > 217     16      0x10    17      0x11
> > > > 215     1       0x01    0       0x00
> > > > 214     218     0xda    238     0xee
> > > > 213     160     0xa0    128     0x80
> > > > 210     10      0x0a    0       0x00
> > > > 209     10      0x0a    60      0x3c
> > > > 208     10      0x0a    0       0x00
> > > > 207     10      0x0a    60      0x3c
> > > > 206     10      0x0a    0       0x00
> > > > 205     10      0x0a    30      0x1e
> > > > 203     0       0x00    51      0x33
> > > > 202     0       0x00    51      0x33
> > > > 201     0       0x00    119     0x77
> > > > 200     0       0x00    119     0x77
> > > > 196     3       0x03    7       0x07
> > > > 194     2       0x02    2       0x02
> > > > 192     5       0x05    5       0x05
> > > > 185     1       0x01    1       0x01
> > > > 181     0       0x00    1       0x01
> > > > 179     0       0x00    1       0x01
> > > > 175     0       0x00    1       0x01
> > > > 169     1       0x01    0       0x00
> > > > 168     0       0x00    2       0x02
> > > > 160     3       0x03    3       0x03
> > > > 158     0       0x00    3       0x03
> > > > 157     237     0xed    186     0xba
> > > >
> > > > The second and the third column is from a device with a Sandisk
> > > > eMCC which works fine, while the last two columns are from a
> > > > Toshiba eMMC which shows the error. Looking into it, I found that
> > > > only the Toshiba eMMC specifies a powerclass in registers 203-200
> > > > while Sandisk does not, so the powerclass is not changed in the
> > > > latter case and the problem cannot be triggered there.
> > > >
> > > > I also attached a boot log with mmc debug enabled. I think there
> > > > is not much I can do else. Either this eMMC is just bogus and
> > > > needs blacklisting or there is some problem in the driver code.
> >
> > I checked the power class specification and MMC core driver handing, I
> > don't see any issue with it. As you mentioned the PWR_CL_* fields are
> > having non-zero values which means SWITCH (CMD6) will be sent to
> > change the POWER_CLASS and from the logs you have attached, this
> > switch command tries to set the POWER_CLASS to 3 which is resulting in
> > SWITCH_ERROR in card and that's why it fails.
> >
> > If the PWR_CL_* fields are 0s (that's the case with SanDisk eMMC as
> > you mentioned), SWITCH(cmd6) is not sent to the card.
> >
> > I was trying to check analyze more from logs and the above EXT_CSD
> > fields for Toshiba card.
> >
> > EXT_CSD[203] => PWR_CL_26_360 => 0x33
> > EXT_CSD[202] => PWR_CL_52_360 => 0x33
> > EXT_CSD[201] => PWR_CL_26_195 => 0x77
> > EXT_CSD[200] => PWR_CL_52_195 => 0x77
> >
> > >> [    3.842382] mmc1: clock 48000000Hz busmode 2 powermode 2 cs 0 Vdd
> 20
> >
> > width 0 timing 1
> > Logs shows that clock = 48MHz, bus_width = 8-Bit, SDR mode, VDD = High
> > voltage range. This would mean power class for this configuration will
> > be in higher nibble of PWR_CL_52_360 field (EXT_CSD[202]) which is 0x3.
> >
> > >> [    3.842390] mmc1: starting CMD6 arg 03bb0301 flags 0000049d
> >
> > "arg" field from this logs show that we are trying to set the
> > POWER_CLASS
> > (EXT_CSD[187]) field to value 0x3 which is resulting in switch error
> > which ideally shouldn't.
> >
> > Just for experiment, can we hack the value set to POWER_CLASS field to
> > 0x7 instead of 0x3? If this doesn't work, you may try other values
> > (starting from 1 till 15) to see setting any of the non-zero value
succeeds or
> not.
> 
> I tried 1 to 10 (as this is a 4.41 card) and none of them worked
(including 7).
> 
> > > > I hope this problem can be fixed or if it can't, I hope that
> > > > commit 3d93576e (mmc: core: skip card initialization if power
> > > > class selection
> > > > fails) is reverted until the issues are sorted out.
> >
> > 3d93576e is really not the issue here. Reverting that patch is just a
> > bad workaround to the problem. We should actually try to find why
> > exactly setting the POWER_CLASS field is failing?
> 
> sure, that would be the best solution...
> 
> Marc
> 
> 
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