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SubjectRe: [PATCH V3] ARM: OMAP2+: omap_device: maintain sane runtime pm status around suspend/resume
Hi,

On Thu, Nov 14, 2013 at 11:05:16AM -0600, 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@ti.com>
> Signed-off-by: Nishanth Menon <nm@ti.com>
> Acked-by: Rajendra Nayak <rnayak@ti.com>
> Acked-by: Kevin Hilman <khilman@linaro.org>
> ---
> Changes in V3:
> - Added WARN in case of unexpected failure of runtime pm status restore
> v2: https://patchwork.kernel.org/patch/3176501/
> v1: https://patchwork.kernel.org/patch/3154501/
>
> patch baseline: V3.12 tag (also applies on linux-next next-20131107 tag)
>
> arch/arm/mach-omap2/omap_device.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/omap_device.c b/arch/arm/mach-omap2/omap_device.c
> index b69dd9a..53f0735 100644
> --- a/arch/arm/mach-omap2/omap_device.c
> +++ b/arch/arm/mach-omap2/omap_device.c
> @@ -621,6 +621,7 @@ static int _od_suspend_noirq(struct device *dev)
>
> if (!ret && !pm_runtime_status_suspended(dev)) {
> if (pm_generic_runtime_suspend(dev) == 0) {
> + pm_runtime_set_suspended(dev);
> omap_device_idle(pdev);
> od->flags |= OMAP_DEVICE_SUSPENDED;
> }
> @@ -634,10 +635,18 @@ 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);
> + /*
> + * XXX: we run before core runtime pm has resumed itself. At
> + * this point in time, we just restore the runtime pm state and
> + * considering symmetric operations in resume, we donot expect
> + * to fail. If we failed, something changed in core runtime_pm
> + * framework OR some device driver messed things up, hence, WARN
> + */
> + WARN(pm_runtime_set_active(dev),
> + "Could not set %s runtime state active\n", dev_name(dev));

if you want to print the device name, how about dev_WARN() ?

no strong feelings though:

Reviewed-by: Felipe Balbi <balbi@ti.com>

--
balbi
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