linux-kernel - Re: [Patch 0/1]drm_irq: Introducing the irq_thread support

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Date:	Wed, 5 Sep 2012 10:47:32 -0500
From:	Rob Clark <rob.clark@...aro.org>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>,
	"'linux-kernel@...r.kernel.org' (linux-kernel@...r.kernel.org)" 
	<linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"alexander.deucher@....com" <alexander.deucher@....com>,
	"airlied@...hat.com" <airlied@...hat.com>,
	"Shi, Yang A" <yang.a.shi@...el.com>
Subject: Re: [Patch 0/1]drm_irq: Introducing the irq_thread support

On Wed, Sep 5, 2012 at 8:27 AM, Daniel Vetter <daniel@...ll.ch> wrote:
> On Wed, Sep 05, 2012 at 01:53:44AM +0000, Liu, Chuansheng wrote:
>> This patch is for introducing the irq thread support in drm_irq.
>>
>> Why we need irq thread in drm_irq code?
>> In our GPU system, the gpu interrupt handler need some time even > 1ms to finish,
>> in that case, the whole system will stay in irq disable status. One case is:
>> when audio is playing, it sometimes effects the audio quality.
>>
>> So we have to introduce the irq thread in drm_irq, it can help us move some heavy work into irq thread
>> and other irq interrupts can be handled in time. Also the IRQF_ONESHOT is helpful for irq thread.
>>
>> Include one patch:
>> [PATCH 01/1] drm_irq-Introducing-the-irq_thread-support
>
> For a kms drm driver (and tbh, doing a non-kms driver today is not a great
> idea), there's no reason to use the drm_irq_install/_unistall helpers.
>
> So if you driver has special needs wrt irq handling that don't neatly fit
> what the drm_irq stuff provides, simply don't use it - all the generic
> code that's there is just to keep non-kms userspace going.

perhaps an easy thing would just be to allow the driver to provide
it's own request_irq?  That might be an easier way for devices that
need to register multiple irq's, etc?

Or is it better to just bypass and dev->irq_enabled=1?  That seemed a
bit like a hack to me, but the current irq code is more framework-ish,
and less helper-ish..

BR,
-R

> Yours, Daniel
> --
> Daniel Vetter
> Mail: daniel@...ll.ch
> Mobile: +41 (0)79 365 57 48
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> dri-devel@...ts.freedesktop.org
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