Tony Lindgren <tony@xxxxxxxxxxx> writes: > * Nishanth Menon <nm@xxxxxx> [131115 05:30]: >> On 11/15/2013 02:07 AM, Paul Walmsley wrote: >> > On Thu, 14 Nov 2013, Nishanth Menon wrote: >> > >> >> OMAP device hooks around suspend|resume_noirq ensures that hwmod >> >> devices are forced to idle using omap_device_idle/enable as part of >> >> the last stage of suspend activity. >> >> >> >> For a device such as i2c who uses autosuspend, it is possible to enter >> >> the suspend path with dev->power.runtime_status = RPM_ACTIVE. >> >> >> >> As part of the suspend flow, the generic runtime logic would increment >> >> it's dev->power.disable_depth to 1. This should prevent further >> >> pm_runtime_get_sync from succeeding once the runtime_status has been >> >> set to RPM_SUSPENDED. >> >> >> >> Now, as part of the suspend_noirq handler in omap_device, we force the >> >> following: if the device status is !suspended, we force the device >> >> to idle using omap_device_idle (clocks are cut etc..). This ensures >> >> that from a hardware perspective, the device is "suspended". However, >> >> runtime_status is left to be active. >> >> >> >> *if* an operation is attempted after this point to >> >> pm_runtime_get_sync, runtime framework depends on runtime_status to >> >> indicate accurately the device status, and since it sees it to be >> >> ACTIVE, it assumes the module is functional and returns a non-error >> >> value. As a result the user will see pm_runtime_get succeed, however a >> >> register access will crash due to the lack of clocks. >> >> >> >> To prevent this from happening, we should ensure that runtime_status >> >> exactly indicates the device status. As a result of this change >> >> any further calls to pm_runtime_get* would return -EACCES (since >> >> disable_depth is 1). On resume, we restore the clocks and runtime >> >> status exactly as we suspended with. These operations are not expected >> >> to fail as we update the states after the core runtime framework has >> >> suspended itself and restore before the core runtime framework has >> >> resumed. >> >> >> >> Reported-by: J Keerthy <j-keerthy@xxxxxx> >> >> Signed-off-by: Nishanth Menon <nm@xxxxxx> >> >> Acked-by: Rajendra Nayak <rnayak@xxxxxx> >> >> Acked-by: Kevin Hilman <khilman@xxxxxxxxxx> >> > >> > Looks reasonable to me. Looks like this should be considered for -stable >> > - Nishanth, what do you think? >> >> Every product kernel since 3.4 needed to be hacked (we have hacked in >> different ways so far) to work around this (since we never spend time >> digging deeper :( ), So, I do agree with your view that a -stable tag >> will be most beneficial. >> >> > >> > Tony or Kevin, do you want to take this one, or want me to? > > I can take it unless you have other fixes pending right now. This version looks good to me. Reviewed-by: Kevin Hilman <khilman@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
