Re: [PATCH] mmc: Added quirks for Ricoh 1180:e823 lower base clock frequency

[Manoj Iyer <manoj.iyer@canonical.com>]

Chris,

Do you know what systems produce these errors? I can look and see if we 
have those for testing your patch.

Cheers
Manoj

On Wed, 21 Nov 2012, Chris Ball wrote:

> Hi Manoj, Matsumuro-san,
>
> On Mon, Jul 18 2011, Manoj Iyer wrote:
>> Right, without the patch I get..
>>
>> [   52.526665] mmc0: new SDHC card at address e624
>> [   52.571228] mmcblk0: mmc0:e624 SD16G 14.8 GiB
>> [   52.591071] mmcblk0: retrying using single block read
>> [   52.593105] mmcblk0: error -84 transferring data, sector 0, nr 8,
>> card status 0x900
>> [   52.593109] end_request: I/O error, dev mmcblk0, sector 0
>> [   52.594594] mmcblk0: error -84 transferring data, sector 1, nr 7,
>> card status 0x900
>> [   52.594604] end_request: I/O error, dev mmcblk0, sector 1
>> [   52.602893] quiet_error: 24 callbacks suppressed
>> [   52.602902] Buffer I/O error on device mmcblk0, logical block 0
>> [   52.605349] ldm_validate_partition_table(): Disk read failed.
>> [   52.605384] Dev mmcblk0: unable to read RDB block 0
>> [   52.607729]  mmcblk0: unable to read partition table
>> u@u:~$
>>
>> So, I cannot generate any comparison data with this SD card.
>
> I don't know if you remember this bug, but I have reports from two users
> who see "error -84"s on :e823 controllers even with this patch active on
> modern ThinkPads.
>
> Maybe 50MHz isn't low enough sometimes?  Is it possible to lower the base
> clock further?
>
> I noticed that the frequency is encoded ine one of the PCI writes:
> +        * 0x32  - 50Mhz new clock frequency
>
> So if I get access to one of these systems, I might try lowering that
> value (by half, say) and see what happens.  But at the moment I haven't
> found someone who's willing to try kernel patches yet, and I don't have
> one of these systems myself.
>
> Thanks!
>
> - Chris.
> -- 
> Chris Ball   <cjb@laptop.org>   <http://printf.net/>
> One Laptop Per Child
>
>

--
====================
Manoj Iyer
Ubuntu/Canonical
Hardware Enablement
====================