new support for Raspberry Pi B+

[Adrian Chadd]

Hi,

can you downgrade the driver speed after it's started?

Ie, once you see a handful of errors, say "ok fine!" and drop down to
the slower speed?


-adrian


On 28 October 2014 05:31, Luiz Otavio O Souza <lists.br at gmail.com> wrote:
> On 26 October 2014 22:09, Dan Raymond wrote:
>> One small correction to my previous test results: with the 16GB Transcend
>> card I *can* get it to boot reliably with the hw.bcm2835.sdhci.hs="0" hack.
>>
>> To summarize, I see no improvement regarding SD card failures between
>> r271779 and r273702.  Nor do I see any improvement between the previous
>> commit to crochet and the current commit.  I do see a minor regression:
>> without the sdhci.hs hack I used to get 50% boot failures on my 16GB
>> Transcend and now I get 100% boot failures.
>
> Dan,
>
> It's not a regression, it is a improvement, but as usual, it uncovered
> another bugs (a bug never come alone).
>
> Try 10 or 15 boots with and without the fix and check the differences
> on the SD card identification at dmesg, it should look like:
>
> mmcsd0: 2GB <SD SU02G 8.0 SN 07018D24 MFG 05/2013 by 3 SD> at mmc0
> 25.0MHz/4bit/65535-block
>
> Without the patch you'll see odd values for bus speed and width in
> some of the boots, they will coincide with the times that your card
> boots fine. What is happening here was that the controller cannot read
> the card identification data and it will switch to safe (and slow)
> defaults.
>
> With the patch the card is always identified with correct speed and
> bus speed, this leads to consistent failures as RPi cannot handle HS
> speed for some cards, whence the the use of hw.bcm2835.sdhci.hs="0" to
> make it work.
>
> So, to summarize:
>
> - The fix improve the card detection and identification, making it reliable.
>
> - The fix does not improve the situation of cards running into errors
> when working at HS.
>
> I'm still chasing other possible bugs in this driver, but no promises.
>
> Luiz
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