[PATCH v4] mmc: meson: Add driver for the SD/MMC host found on Amlogic MesonX SoCs

[Carlo Caione]

On Wed, Feb 3, 2016 at 11:46 AM, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> On 2 February 2016 at 22:54, Carlo Caione <carlo at caione.org> wrote:

[cut]

> Huh, another broken MMC controller. :-)

Oh, actually I found in the datasheet a couple of undocumented
registers (also not used in the original Amlogic SDK code) that seems
to have something to do with timeout (hard to say without proper
documentation but they are called "Timeout counter for preload setting
and present status" and "Timeout Counter Interrupt Enable for ARC/ARM"
so I guess I'm on the right track here).
I briefly tried yesterday to enable this timeout interrupt with a
dummy value in the counter register (I have no idea how get this value
from the clocking) and it seems working (the counter value is
decremented when reading the register upon command completion).

> In some cases there are no data in the request, it's just a command
> being sent. So to deal with this issue, you will have to adjust the
> timer depending on the request we send to the controller.

I see that the CMD13 used to poll the card has no data so in that case
should we use a fixed / dummy value to use as timeout counter?
I'm kind of confused here since the MMC drivers I'm looking at use the
hardware timeout register only when the data->timeout_ns is actually
present.

-- 
Carlo Caione