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

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Message-ID: <592501c9-2d94-b266-ae76-e383d3bffa29@ti.com>
Date:   Tue, 16 Jun 2020 16:01:39 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Grygorii Strashko <grygorii.strashko@...com>,
        Tony Lindgren <tony@...mide.com>
CC:     <linux-omap@...r.kernel.org>, "Andrew F . Davis" <afd@...com>,
        Dave Gerlach <d-gerlach@...com>,
        Faiz Abbas <faiz_abbas@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Keerthy <j-keerthy@...com>, Nishanth Menon <nm@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Roger Quadros <rogerq@...com>, Suman Anna <s-anna@...com>,
        Tero Kristo <t-kristo@...com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <dri-devel@...ts.freedesktop.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH 1/5] drm/omap: Fix suspend resume regression after
 platform data removal

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

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