Re: [PATCH 0/1] drm/i915: Enable fastset by default, except on initial modeset

From: Hans de Goede <hdegoede@redhat.com>
To: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 0/1] drm/i915: Enable fastset by default, except on initial modeset
Date: Tue, 18 Dec 2018 17:07:34 +0100	[thread overview]
Message-ID: <43d1efb5-f3f8-211f-e7b6-8aa3cf87cdcd@redhat.com> (raw)
In-Reply-To: <20181217184324.GB54091@intel.com>

Hi,

On 17-12-18 19:43, Rodrigo Vivi wrote:
> On Mon, Dec 17, 2018 at 03:23:14PM +0100, Hans de Goede wrote:
>> Hi All,
>>
>> As discussed a while ago, I would like to see us enable fastboot by
>> default, starting with Skylake / GEN9 and newer hardware, so that we can
>> avoid an unnecessary modeset at boot and move to a truely flickerfree boot.
>>
>> During our previous discussion about this Maarten mentioned that a first
>> step would be to get this patch from him upstream. So I'm hereby
>> resubmitting it, with a small fix. Hopefully the CI will like it better
>> this time (if not we will need to investigate) and once this passes CI
>> I hope this can be reviewed quickly and we can get this upstream.
> 
> I honestly believe the first step is to make sure FBC, PSR, DRRS features > gets enabled somehow with fastboot.

That is a good point, FBC will already be enabled on a fastboot as
intel_update_crtc does:

         if (new_plane_state)
                 intel_fbc_enable(intel_crtc, pipe_config, new_plane_state);

Independent of need_modeset() returning true.

PSR indeed stays off, even if i915.enable_psr=1 is passed on the kernel
commandline. I've just completed writing a patch-set (2 patches) fixing
this. I will submit these upstream soon.

DRRS seems to be the same as PSR (I don't have hw to test) I will also
submit 2 patches building on top of the previous 2 which should fix this,
we already allow runtime enabling/disabling through i915_drrs_ctl in
debugfs, so these 2 patches should be fine.

> Maybe DSC as well?!

DSC? :

[hans@shalem linux]$ grep -r dsc  drivers/gpu/drm/i915
[hans@shalem linux]$

> Right now as I can remember FBC, PSR, and DRRS will get disabled if fastboot
> is used because we just enable those when enabling the pipe.

You're right for PSR and DRRS, as Maarten just found out FBC has the
opposite problem, we don't turn it off on a fastset when it was enabled and we
decide it should no longer be enabled.

Regards,

Hans

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