Re: power class selection fails on 3.5-rc1

[Marc Dietrich <marvin24@gmx.de>]

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