Re: [PATCH] mmc: core: Remove timeout when enabling cache

[Faiz Abbas]

Hi Sjoerd,

On Tuesday 06 November 2018 07:00 PM, Sjoerd Simons wrote:
> On some of our boards containing Micron eMMC chips compatible with
> the eMMC 5.0 specification we starting seeing boot failures due to
> timeouts:
>   mmc1: error -110 whilst initialising MMC card
> 
> It turns out that switching the cache on after a power loss event can
> take quite long. In some simple testing thusfar we've seen values up to
> 700ms, which is far longer then the GENERIC_CMD6_TIME of the chip
> (250ms).
> 
> Looking at both the eMMC 4.51 and 5.0 specification there doesn't seem
> to be a defined upper bound for the CACHE_CTRL ON command. For both
> CACHE_CTRL OFF and FLUSH_CACHE it is documented that they can take
> essentially unbounded time, but CACHE_CTRL ON i get the impression that
> it's assumed to be "fast". Unfortunately this is not true in reality.
> 
> To resolve this, simply drop the timeout from CACHE_CTRL ON and assume
> it might take an unbounded time similar to the FLUSH_CACHE command.
> 
> Signed-off-by: Sjoerd Simons <sjoerd.simons@xxxxxxxxxxxxxxx>
> 

I have the exact same problem with micron cards. Specifically with CID: 
R1J56L

The correct way to solve this would be to add a quirk for the specific 
card. Does this patch solve your issue?

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