Hi Chris:
Thanks for the comments that extends our knowledge about this modification. Really appreciate the help. But is it possible that we still need an ordinary gpu reset here? Consider that we may modprobe i915 with i915.enable_execlists=1 then unload it, then modprobe i915.enable_execlists=0, according to bspec, changing execlist mode to ringbuffer mode, a hardware reset is needed?
Thanks,
Zhi.
> -----Original Message-----
> From: Intel-gfx [mailto:intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of
> Chris Wilson
> Sent: Thursday, June 25, 2015 4:13 PM
> To: Niu, Bing
> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH] drm/i915: Also perform gpu reset under execlist
> mode.
>
> On Thu, Jun 25, 2015 at 10:40:15PM +0800, bing.niu@xxxxxxxxx wrote:
> > From: "Niu,Bing" <bing.niu@xxxxxxxxx>
> >
> > It is found that i915 will not reset gpu under execlist mode when
> > unload module. that will lead to some issues when unload/load module
> > with different submission mode. e.g. from execlist mode to ring buffer
> > mode via loading/unloading i915. Because HW is not in a reset state
> > and registers are not clean under such condition.
>
> Now the reason we have the reset there is to disable writes to the power
> context after the memory is released. Your complaint above can easily be read
> as the driver is unable to correctly initialisae itself from a random GPU state,
> which is a fault in driver initialisation.
>
> Have you observed stray memory writes from the GPU after the module is
> unloaded? If not, this would seem to be just a band-aid.
> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
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