On Thursday, June 14, 2012, Laurent Pinchart wrote:

Hi Magnus,

On Thursday 14 June 2012 20:12:33 Magnus Damm wrote:

quoted

On Tue, Jun 12, 2012 at 9:57 PM, Laurent Pinchart wrote:

quoted

The tmio_mmc_set_ios() function configures the MMC power, clock and bus
width. When the MMC controller gets powered off, runtime PM switches the
MSTP clock off. Writing to to CTL_SD_MEM_CARD_OPT register afterwards
fails and prints an error message to the kernel log.

As configuring the bus width is pointless when the interface gets
powered down, skip the operation when power is off.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

First of all, thanks for reporting this issue and coming up with a fix!

You're welcome. You can expect more of them ;-)

quoted

Can you please explain a bit more about when this triggers? Is this
related to suspend-to-ram perhaps? Which hardware platform? Is
CONFIG_PM_RUNTIME=y set?

I've noticed the problem on the Armadillo board with CONFIG_PM_RUNTIME=y. The 
driver spits out "timeout waiting for SD bus idle" error messages more or less 
continuously.

quoted

I suspect that this may be a side effect of the current PM code used
on the A1 SoC (which is hooked up on the armadillo board).

In short, the A1 SoC does not yet make use of PM domains, but AP4 and
the mackerel board (sh7372 based) is using PM domains.

Does this mean that runtime PM is a no-op on A1 ? That would surprise me, as 
turning CONFIG_PM_RUNTIME off gets rid of the problem, so runtime PM is 
somehow involved. Even if the power domain does not get turned off, can't the 
MSTP clock be turned off ?

The problem is, most likely, that with CONFIG_PM_RUNTIME set the code in
drivers/sh/pm_runtime.c triggers and that causes default_pm_domain to be
used.

So, I don't really think we need to "fix" every driver in turn,
default_pm_domain seems to be what needs fixing.  I'm not exactly sure
how to fix it at the moment, though.

You can verify if my suspicion is correct quite easily by replacing the
(&default_pm_domain) in drivers/sh/pm_runtime.c with NULL.

Thanks,
Rafael