lkml.org 
[lkml]   [2009]   [Jan]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] Fixes and enhancements for the MMC SPI driver
Date
Matt,

I think I should explain a little bit more the situation with the current
implementation of the MMC SPI driver...

The SPI mode is not used widely to drive SD cards. Most SD capable devices are
using 1 bit or 4 bit SD mode. SPI mode is only used by some embedded devices
which have no native SD host controller.

So, in practice, most of the available SD cards have bugs in the SPI mode.
These bugs are unlikely to fix by the SD card vendors because SPI mode is not
in focus. In general, Sandisk has the best SPI mode.

The current MMC SPI driver without my patch was able to work with only ONE of
my cards (a new microSD card from Sandisk). All other cards failed. Common
causes of failure are implementation bugs in the SD card: missing response
timing or timeouts.

With my patch applied, all of my available cards (with the exception of one
card which fails because of a bit offset error in reading blocks) are
working. For the bit-offset error, I have found no easy and performant
solution. (You have to bitshift the whole datastream).

So, essential, all of my patch is for common SPI bugs in SD cards - not only
the timeout adjust you comlpained about.

So, my patch changes the status of the MMC SPI driver from "don't work for the
majority of cards" to "work for the majority of cards".

best regards
 
i. A. Wolfgang Mües
--
Auerswald GmbH & Co. KG
Hardware Development
Telefon: +49 (0)5306 9219 0
Telefax: +49 (0)5306 9219 94
E-Mail: Wolfgang.Mues@Auerswald.de
Web: http://www.auerswald.de
 
--------------------------------------------------------------
Auerswald GmbH & Co. KG, Vor den Grashöfen 1, 38162 Cremlingen
Registriert beim AG Braunschweig HRA 13289
p.h.G Auerswald Geschäftsführungsges. mbH
Registriert beim AG Braunschweig HRB 7463
Geschäftsführer: Dipl-Ing. Gerhard Auerswald
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2009-01-12 11:53    [W:0.250 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site