Re: [PATCH] New AT91 MCI Driver that supports both MCI slots used at the same time

Nicolas Ferre
2009-06-03T15:11:02Z

Rob Emanuele :
> Greetings Joey,

>>> + if (host->need_reset) {
>>> + at91_mci_write(host, AT91_MCI_CR, AT91_MCI_SWRST);
>>> + at91_mci_write(host, AT91_MCI_CR, AT91_MCI_MCIEN);
>>> + at91_mci_write(host, AT91_MCI_MR, host->mode_reg);
>>> + host->need_reset = false;
>>> + }
>>>
>> In my experience some at91s need a reset after every single command,
>> otherwise bad things happen. I think the need_reset logic is too
>> conservative in this driver.
>
> I'll try this and probably make it an option to always reset before
> each command.

This systematic reset was remove by Haavard with this comment:
"Also, don't reset the controller between each transfer. That was an
attempt to work around earlier bugs, and it never really worked very
well."

http://lkml.org/lkml/2008/10/5/152

This reset remains in at91_mci and it does improve things on this driver
but I do not know it a better written driver can prevent from doing this...

>>> + /*
>>> + * WRPROOF and RDPROOF prevent overruns/underruns by
>>> + * stopping the clock when the FIFO is full/empty.
>>> + * This state is not expected to last for long.
>>> + */
>>> + host->mode_reg = (AT91_MCI_CLKDIV & clkdiv) |
>>> AT91_MCI_WRPROOF
>>> + | AT91_MCI_RDPROOF;
>>>
>> These registers are not in all at91 chips especially the at91sam9261.
>
> I'll look into this but will not be able to test every case.

Only at91rm9200 & at91sam9261/9261s are unable to setup these
functionalities.

Best regards,
--
Nicolas Ferre