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

From: Grygorii Strashko <grygorii.strashko@ti.com>
To: Tomi Valkeinen <tomi.valkeinen@ti.com>, Tony Lindgren <tony@atomide.com>
Cc: <linux-omap@vger.kernel.org>, "Andrew F . Davis" <afd@ti.com>,
	Dave Gerlach <d-gerlach@ti.com>, Faiz Abbas <faiz_abbas@ti.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Keerthy <j-keerthy@ti.com>, Nishanth Menon <nm@ti.com>,
	Peter Ujfalusi <peter.ujfalusi@ti.com>,
	Roger Quadros <rogerq@ti.com>, Suman Anna <s-anna@ti.com>,
	Tero Kristo <t-kristo@ti.com>, <linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<dri-devel@lists.freedesktop.org>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Subject: Re: [PATCH 1/5] drm/omap: Fix suspend resume regression after platform data removal
Date: Wed, 17 Jun 2020 15:49:59 +0300	[thread overview]
Message-ID: <8404d47b-33bb-499f-4d50-33501e7c5921@ti.com> (raw)
In-Reply-To: <d0488631-e2d8-115f-9900-5838147ec674@ti.com>


On 17/06/2020 09:04, Tomi Valkeinen wrote:
> On 16/06/2020 19:56, Grygorii Strashko wrote:
>>
>>
>> On 16/06/2020 18:30, Tony Lindgren wrote:
>>> * Tomi Valkeinen <tomi.valkeinen@ti.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?

noirq is *not* atomic, jus IRQs (non-wakeup) will be disabled (disbale_irq())

> 
> 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.


-- 
Best regards,
grygorii