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

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Date:   Wed, 17 Jun 2020 09:04:56 +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 16/06/2020 19:56, Grygorii Strashko wrote:
> 
> 
> On 16/06/2020 18:30, Tony Lindgren wrote:
>> * Tomi Valkeinen <tomi.valkeinen@...com> [200616 13:02]:
>>> On 11/06/2020 17:00, Grygorii Strashko wrote:
>>>> 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?
>>
>> Well up to you as far as I'm concerned. The noirq phase comes with serious
>> limitations, for let's say i2c bus usage if needed. Probably also harder
>> to debug for suspend and resume.
> 
> Unfortunately, you can't use PM runtime force API at .suspend() stage as pm_runtime_get will still 
> work and
> there is no sync between suspend and pm_runtime.
> The PM runtime force API can be used only during late/noirq as at this time pm_runtime is disabled.

Yes, but which one... Do you know what the diff is with late/noirq from driver's perspective? I 
guess noirq is atomic context, late is nto?

Dispc's suspend uses synchronize_irq(), so that rules out noirq. Although the call is not needed if 
using noirq version, so that could also be managed with small change. But I wonder if there's any 
benefit in using noirq versus late.

  Tomi

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