Hello,

On 2015-01-29 11:56, Javier Martinez Canillas wrote:

On Thu, Jan 29, 2015 at 10:15 AM, Marek Szyprowski
[off-list ref] wrote:

quoted

quoted

Also, I wonder whether we could extend the mmc-pwrseq to cover your
case? Did you consider that as an option?

I didn't consider mmc-pwrseq yet. For me it looked straightforward to

I agree with Ulf that using mmc-pwrseq would be a good solution and in
fact I think the pwrseq_simple [0] driver will fit your use case since
it supports a reset GPIO pin which is what many WLAN chips attached to
a SDIO interface use.

quoted

implement
it just like card detect or write-protection gpio pins. I already noticed
that
there is code for some mmc host driver, which perform mmc hardware reset. If
you
think that extending pwrseq is the better approach, I will try to update my
patches. This will add reboot handler to mmc-pwrseq then. The only question
is

I don't think that adding a reboot handler to mmc-pwrseq is needed.
AFAICT the call chain is:

sys_reboot() -> kernel_restart() -> device_shutdown() ->
mmc_bus_shutdown() -> _mmc_suspend() -> mmc_power_off() ->
mmc_pwrseq_power_off() -> struct mmc_pwrseq_ops .power_off

So since the pwrseq_simple already asserts the reset GPIO in
.power_off, it should be enough to ensure the eMMC will be reset to
its default configuration for the iROM to work properly.

I think that I had to add reset handler, because device_shutdown() was not
called if reset was triggered from magic sysrq, but I will check it again.

It also asserts the GPIO pin in .pre_power_on and de-asserts in
.post_power_on which should be needed as well for the other case you
mentioned when a broken bootloader left the emmc card in some unknown
state.

quoted

weather to use it always when mmc-pwrseq has been enabled or only if some
additional property like 'reset-on-reboot' has been provided.

Having a reset GPIO is optional AFAIK so I don't think there is a need
for an additional "reset-on-reboot" propery.

quoted

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Best regards,
Javier

[0]:
FYI, these are the relevant commits in linux-next:
fe1922d5d4d0 mmc: pwrseq_simple: Add support for a reset GPIO pin
ec2017f2491f mmc: pwrseq: Initial support for the simple MMC power
sequence provider
fe1686658f9c mmc: pwrseq: Document DT bindings for the simple MMC power sequence
1b745e8a4627 mmc: core: Initial support for MMC power sequences

Ok, I will check it.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland