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. Reported-by: J Keerthy <[email protected]> Signed-off-by: Nishanth Menon <[email protected]> Acked-by: Rajendra Nayak <[email protected]> --- patch baseline: V3.12 tag (also applies on linux-next next-20131107 tag) Logs from 3.12 based vendor kernel: Before: http://pastebin.com/m5KxnB7a After: http://pastebin.com/8AfX4e7r The discussion on cpufreq side of the story which triggered this scenario: http://marc.info/?l=linux-pm&m=138263811321921&w=2 Tested on TI vendor kernel (with dt boot): AM335x: evm, BBB, sk, BBW OMAP5uEVM, DRA7-evm arch/arm/mach-omap2/omap_device.c | 16 ++++++++++++++-- arch/arm/mach-omap2/omap_device.h | 1 + 2 files changed, 15 insertions(+), 2 deletions(-) diff --git a/arch/arm/mach-omap2/omap_device.c b/arch/arm/mach-omap2/omap_device.c index b69dd9a..87ecbb0 100644 --- a/arch/arm/mach-omap2/omap_device.c +++ b/arch/arm/mach-omap2/omap_device.c @@ -621,6 +621,13 @@ static int _od_suspend_noirq(struct device *dev) if (!ret && !pm_runtime_status_suspended(dev)) { if (pm_generic_runtime_suspend(dev) == 0) { + if (!pm_runtime_suspended(dev)) { + /* NOTE: *might* indicate driver race */ + dev_dbg(dev, "%s: Force suspending\n", + __func__); + pm_runtime_set_suspended(dev); + od->flags |= OMAP_DEVICE_SUSPEND_FORCED; + } omap_device_idle(pdev); od->flags |= OMAP_DEVICE_SUSPENDED; } @@ -634,10 +641,15 @@ static int _od_resume_noirq(struct device *dev) struct platform_device *pdev = to_platform_device(dev); struct omap_device *od = to_omap_device(pdev); - if ((od->flags & OMAP_DEVICE_SUSPENDED) && - !pm_runtime_status_suspended(dev)) { + if (od->flags & OMAP_DEVICE_SUSPENDED) { od->flags &= ~OMAP_DEVICE_SUSPENDED; omap_device_enable(pdev); + + if (od->flags & OMAP_DEVICE_SUSPEND_FORCED) { + pm_runtime_set_active(dev); + od->flags &= ~OMAP_DEVICE_SUSPEND_FORCED; + } + pm_generic_runtime_resume(dev); } diff --git a/arch/arm/mach-omap2/omap_device.h b/arch/arm/mach-omap2/omap_device.h index 17ca1ae..45885b0 100644 --- a/arch/arm/mach-omap2/omap_device.h +++ b/arch/arm/mach-omap2/omap_device.h @@ -38,6 +38,7 @@ extern struct dev_pm_domain omap_device_pm_domain; /* omap_device.flags values */ #define OMAP_DEVICE_SUSPENDED BIT(0) +#define OMAP_DEVICE_SUSPEND_FORCED BIT(1) /** * struct omap_device - omap_device wrapper for platform_devices -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
