Re: [PATCH 1/5] drm/omap: Fix suspend resume regression after platform data removal

Tomi Valkeinen
2020-06-16T13:02:12Z

On 11/06/2020 17:00, Grygorii Strashko wrote:
>
>
> On 09/06/2020 18:26, Tomi Valkeinen wrote:
>> On 09/06/2020 18:19, Tony Lindgren wrote:
>>>> But there's an extra runtime PM reference (dev.power.usage_count) that seems
>>>> to come out of nowhere. So when omap_drm_suspend is finished, there's still
>>>> usage_count of 1, and dispc never suspends fully.
>>>
>>> Hmm no idea about that. My guess is that there might be an issue that was
>>> masked earlier with omap_device calling the child runtime_suspend.
>>
>> Yes. It's how PM works. It calls pm_runtime_get_noresume() before starting the suspend of a
>> device. So I guess omapdrm's suspend has been broken all the time, but it was "fixed" by omap_device.
>>
>
> I think I might have an idea what is going wrong.
>
> Before:
> +----------------------+
> |omap_device_pm_domain |
> +---------------+------+------+
>                 | device      |
>                 +-------------+
>                 | omap_device |
>                 +-------------+
>
> omap_device is embedded in DD device and PM handled by omap_device_pm_domain.
>
> static int _od_suspend_noirq(struct device *dev)
> {
> ...
>
>     ret = pm_generic_suspend_noirq(dev);
> [1] ^^ device suspend_noirq call
>
>     if (!ret && !pm_runtime_status_suspended(dev)) {
>         if (pm_generic_runtime_suspend(dev) == 0) {
> [2] ^^ device pm_runtime_suspend force call
>
>             omap_device_idle(pdev);
> [3] ^^ omap_device disable
>             od->flags |= OMAP_DEVICE_SUSPENDED;
>         }
>     }
>
>     return ret;
> }
>
> Now:
> +------------+
> |ti sysc dev |
> +-+----------+
>   |
>   |
>   |   +-------------+
>   |   | device      |
>   +-->+             |
>       +-------------+
>
> With new approach the omap_device is not embedded in DD Device anymore,
> instead ti-sysc (hwmod replacement) became parent of DD Device.
>
> As result suspend sequence became the following
> (Note. All PM runtime PUT calls became NOP during suspend by design):
>
> device
> |-> suspend() - in case of dss omap_drm_suspend() and Co if defined
> |-> suspend_noirq() - in case of dss *not defined", equal to step [1] above
> ..
>
> ti sysc dev (ti-sysc is parent, so called after device)
> |-> sysc_noirq_suspend
>    |-> pm_runtime_force_suspend()
>     |-> sysc_runtime_suspend() - equal to step [3] above
>
> And step [2] is missing as of now!
>
> I think, suspend might be fixed if all devices, which are now child of ti-sysc, will do
> pm_runtime_force_xxx() calls at noirq suspend stage by adding:
>
>     SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>                       pm_runtime_force_resume)
>
> Am I missing smth?

Isn't this almost exactly the same my patch does? I just used suspend_late and resume_early. Is
noirq phase better than late & early?

Tomi

--
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki