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Subject: Re: [PATCH v3 0/3] Reduce context clear batch size to avoid gpu hang
To:     rwright@hpe.com, jani.nikula@linux.intel.com,
        joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com,
        airlied@linux.ie, daniel@ffwll.ch, sumit.semwal@linaro.org,
        christian.koenig@amd.com, wambui.karugax@gmail.com,
        chris@chris-wilson.co.uk, matthew.auld@intel.com,
        akeem.g.abodunrin@intel.com, prathap.kumar.valsan@intel.com,
        mika.kuoppala@linux.intel.com
Cc:     intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org
References: <20201101174132.10513-1-rwright@hpe.com>
From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <8cdf0dd0-2a2f-bae9-71ea-89a88fdb14a5@redhat.com>
Date:   Mon, 2 Nov 2020 10:48:54 +0100
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Hi,

On 11/1/20 6:41 PM, rwright@hpe.com wrote:
> From: Randy Wright <rwright@hpe.com>
> 
> For several months, I've been experiencing GPU hangs when  starting
> Cinnamon on an HP Pavilion Mini 300-020 if I try to run an upstream
> kernel.  I reported this recently in
> https://gitlab.freedesktop.org/drm/intel/-/issues/2413 where I have
> attached the requested evidence including the state collected from
> /sys/class/drm/card0/error and debug output from dmesg.
> 
> I ran a bisect to find the problem, which indicates this is the
> troublesome commit:
> 
>   [47f8253d2b8947d79fd3196bf96c1959c0f25f20] drm/i915/gen7: Clear all EU/L3 residual contexts
> 
> The nature of that commit suggested to me that reducing the
> batch size used in the context clear operation might help this
> relatively low-powered system to avoid the hang.... and it did!
> I simply forced this system to take the smaller batch length that is
> already used for non-Haswell systems.
> 
> The first two versions of this patch were posted as RFC
> patches to the Intel-gfx list, implementing the same
> algorithmic change in function batch_get_defaults,
> but without employing a properly constructed quirk.
> 
> I've now cleaned up the patch to employ a new QUIRK_RENDERCLEAR_REDUCED.
> The quirk is presently set only for the aforementioned HP Pavilion Mini
> 300-020.  The patch now touches three files to define the quirk, set it,
> and then check for it in function batch_get_defaults.

Note I'm not really an i915 dev.

With that said I do wonder if we should not use the
reduced batch size in a lot more cases, the machine in question uses a
3558U CPU if the iGPU of that CPU has this issue, then I would expect
pretty much all Haswell U models (at a minimum) to have this issue.

So solving this with a quirk for just the HP Pavilion Mini 300-020
seems wrong to me. I think we need a more generic way of enabling
the reduced batch size. I even wonder if we should not simply use
it everywhere. Since you do have a proper Haswell CPU, I guess
it being an U model makes the hang easier to trigger, but I suspect
the higher TPD ones may also still be susceptible ...

Regards,

Hans