Re: [PATCH 1/4] mmc: tmio: Implement SDIO IRQ

[Arnd Hannemann <arnd@arndnet.de>]

Hi Magnus,

Am 07.12.2010 00:39, schrieb Magnus Damm:
> Hi Arnd,
> 
> On Tue, Dec 7, 2010 at 2:35 AM, Arnd Hannemann <arnd@arndnet.de> wrote:
>> This patch implements SDIO IRQ support for mfds which
>> announce the MMC_CAP_SDIO_IRQ capability for tmio_mmc.
>> Tested with a b43-based wireless SDIO card and sh_mobile_sdhi.
>>
>> This patch applies on top of:
>> mmc: tmio_mmc: allow multi-element scatter-gather lists
>> mmc: tmio_mmc: fix PIO fallback on DMA descriptor allocation failure
>> mmc: tmio: merge the private header into the driver
>> mmc: tmio: implement a bounce buffer for unaligned DMA
>>
>> Signed-off-by: Arnd Hannemann <arnd@arndnet.de>
>> CC: Ian Molton <ian@mnementh.co.uk>
>> CC: Samuel Ortiz <sameo@linux.intel.com>
>> CC: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
>> ---
>>  drivers/mmc/host/tmio_mmc.c |   54 ++++++++++++++++++++++++++++++++++++++++++-
>>  1 files changed, 53 insertions(+), 1 deletions(-)
> 
> Thanks for your work on this!
> 
> Just curious, did you test this change in 4-bit mode and/or 1-bit
> mode? I believe that 1-bit mode support is rather simple, but 4-bit
> mode requires toggling between the IRQ and DATA function which happen
> to be using the same pin. It looks like the current code only deals
> with 1-bit mode - perhaps 4-bit mode isn't supported by the b43
> driver?

Yes, I tested this in 1-bit and 4-bit mode. At least the card claims it is using it,
it says "width=2". I also read about the toggling, and expected to do
something fancy, but when tests where successful I came to the conclusion
that the controller does the toggling for us. Do you believe otherwise?

> Not sure how the Linux MMC stack supports 4-bit IRQs, but the S4MI bit
> in the CCCR should specify if it's allowed to enable interrupts in
> between data transfers or not. Perhaps that is something we need to
> deal with in the driver? Or maybe the framework needs to be extended?

I quick grep shows that nobody seems to care about this bit until now...

Thanks,
Arnd