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From: Keith Packard <keithp@keithp.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	linux-kernel@vger.kernel.org,
	Lubos Kolouch <lubos.kolouch@gmail.com>
Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915: Force explicit bpp selection for intel_dp_link_required
Date: Wed, 25 Jan 2012 14:45:44 -0800	[thread overview]
Message-ID: <867h0fcsfb.fsf@sumi.keithp.com> (raw)
In-Reply-To: <20120125215054.GI3896@phenom.ffwll.local>


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On Wed, 25 Jan 2012 22:50:55 +0100, Daniel Vetter <daniel@ffwll.ch> wrote:

> I think we could compute this in crtc->mode_fixup (crtc->prepare doesn't
> have the mode and adjusted_mode arguments). We could then store the
> computed bpc and dithering in one of the private fields. We'd still have
> to loop over all encoders, but alas ...

Alas, intel_crtc_mode_fixup is called *after* the intel_dp_mode_fixup. So,
we'd either need to change drm_crtc_helper, or have
intel_crtc_mode_fixup call down into intel_dp.c to set the link
parameters. In either case, ick.

> Afaics we'll still correctly fall back to 6bpc (undithered for 16bpp
> obviously) and hence things should keep on working.

Right, the problem is that the DP link parameters will be set to support
24bpp color, so we'll use a higher clock/lane-count than strictly
necessary as intel_dp_mode_fixup doesn't take the frame buffer format
into consideration when computing the link values.

> Yeah, there are a few rough corners with the bpc computation in patch 2.
> I'll try to throw around a few ideas that crossed my mind while reading
> through it in a reply there.

Thanks. I'm not happy with it either.

In short, I think we can (and should) apply the simple first patch to
drm-intel-fixes so that at least displays work consistently, and then
come up with a nicer patch that computes correct link parameters, and
also supports 10bpc formats.

-- 
keith.packard@intel.com

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WARNING: multiple messages have this Message-ID (diff)
From: Keith Packard <keithp@keithp.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>,
	intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org,
	Lubos Kolouch <lubos.kolouch@gmail.com>
Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915: Force explicit bpp selection for intel_dp_link_required
Date: Wed, 25 Jan 2012 14:45:44 -0800	[thread overview]
Message-ID: <867h0fcsfb.fsf@sumi.keithp.com> (raw)
In-Reply-To: <20120125215054.GI3896@phenom.ffwll.local>

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On Wed, 25 Jan 2012 22:50:55 +0100, Daniel Vetter <daniel@ffwll.ch> wrote:

> I think we could compute this in crtc->mode_fixup (crtc->prepare doesn't
> have the mode and adjusted_mode arguments). We could then store the
> computed bpc and dithering in one of the private fields. We'd still have
> to loop over all encoders, but alas ...

Alas, intel_crtc_mode_fixup is called *after* the intel_dp_mode_fixup. So,
we'd either need to change drm_crtc_helper, or have
intel_crtc_mode_fixup call down into intel_dp.c to set the link
parameters. In either case, ick.

> Afaics we'll still correctly fall back to 6bpc (undithered for 16bpp
> obviously) and hence things should keep on working.

Right, the problem is that the DP link parameters will be set to support
24bpp color, so we'll use a higher clock/lane-count than strictly
necessary as intel_dp_mode_fixup doesn't take the frame buffer format
into consideration when computing the link values.

> Yeah, there are a few rough corners with the bpc computation in patch 2.
> I'll try to throw around a few ideas that crossed my mind while reading
> through it in a reply there.

Thanks. I'm not happy with it either.

In short, I think we can (and should) apply the simple first patch to
drm-intel-fixes so that at least displays work consistently, and then
come up with a nicer patch that computes correct link parameters, and
also supports 10bpc formats.

-- 
keith.packard@intel.com

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  reply	other threads:[~2012-01-25 22:45 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-25 16:16 [PATCH 0/2] drm/i915: Use correct bpc computations for DisplayPort Keith Packard
2012-01-25 16:16 ` [PATCH 1/2] drm/i915: Force explicit bpp selection for intel_dp_link_required Keith Packard
2012-01-25 16:16   ` Keith Packard
2012-01-25 20:51   ` [Intel-gfx] " Jesse Barnes
2012-01-25 21:17     ` Keith Packard
2012-01-25 21:50       ` Daniel Vetter
2012-01-25 21:50         ` [Intel-gfx] " Daniel Vetter
2012-01-25 22:45         ` Keith Packard [this message]
2012-01-25 22:45           ` Keith Packard
2012-01-25 21:52   ` Daniel Vetter
2012-01-27 10:30   ` Daniel Vetter
2012-02-06 12:12     ` Dave Airlie
2012-02-06 16:03       ` Daniel Vetter
2012-02-06 22:10       ` Keith Packard
2012-01-25 16:16 ` [PATCH 2/2] drm/i915: Select DP BPC at mode set, rather than mode validate Keith Packard
2012-01-25 16:22   ` Monark Gondaliya
2012-01-25 22:11   ` [Intel-gfx] " Daniel Vetter
2012-01-25 22:56     ` Keith Packard

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