Hi Rafael, On Thursday 14 June 2012 21:37:26 Rafael J. Wysocki wrote: > On Thursday, June 14, 2012, Laurent Pinchart wrote: > > On Thursday 14 June 2012 20:12:33 Magnus Damm wrote: > > > On Tue, Jun 12, 2012 at 9:57 PM, Laurent Pinchart wrote: > > > > 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@xxxxxxxxxxxxxxxx> > > > > > > First of all, thanks for reporting this issue and coming up with a fix! > > > > You're welcome. You can expect more of them ;-) > > > > > 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. > > > > > 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. But isn't there still an issue in the driver itself ? If my understanding is correct, calling pm_runtime_put() essentially means "I won't need to touch the device from now on, it can be suspended it needed/useful/appropriate/whatever". The runtime PM core is then free to turn the power domain and/or clock off synchronously or with a delay, or do nothing. After signaling that it won't need to touch the device, the driver should really avoid touching the device until the next pm_runtime_get_sync() call. > You can verify if my suspicion is correct quite easily by replacing the > (&default_pm_domain) in drivers/sh/pm_runtime.c with NULL. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
