From: Peter Rosin <peda@axentia.se>
To: linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org,
intel-gfx@lists.freedesktop.org, nouveau@lists.freedesktop.org,
dri-devel@lists.freedesktop.org,
"Philippe Cornu" <philippe.cornu@st.com>,
"Christian König" <christian.koenig@amd.com>,
"Yannick Fertre" <yannick.fertre@st.com>,
"Gerd Hoffmann" <kraxel@redhat.com>,
"Daniel Vetter" <daniel.vetter@intel.com>,
"Alex Deucher" <alexander.deucher@amd.com>,
"Dave Airlie" <airlied@redhat.com>,
virtualization@lists.linux-foundation.org,
"Vincent Abriou" <vincent.abriou@st.com>,
"Ben Skeggs" <bskeggs@redhat.com>
Subject: Re: [PATCH 01/11] drm/fb-helper: do a generic fb_setcmap helper in terms of crtc .gamma_set
Date: Thu, 22 Jun 2017 10:48:10 +0200 [thread overview]
Message-ID: <854a89af-d146-8414-73e7-2460c8f33598@axentia.se> (raw)
In-Reply-To: <20170622063645.k5ciwdeqfafgnxtv@phenom.ffwll.local>
On 2017-06-22 08:36, Daniel Vetter wrote:
> On Wed, Jun 21, 2017 at 11:40:52AM +0200, Peter Rosin wrote:
>> On 2017-06-21 09:38, Daniel Vetter wrote:
>>> On Tue, Jun 20, 2017 at 09:25:25PM +0200, Peter Rosin wrote:
>>>> This makes the redundant fb helpers .load_lut, .gamma_set and .gamma_get
>>>> totally obsolete.
>>>>
>>>> I think the gamma_store can end up invalid on error. But the way I read
>>>> it, that can happen in drm_mode_gamma_set_ioctl as well, so why should
>>>> this pesky legacy fbdev stuff be any better?
>>>>
>>>> drm_fb_helper_save_lut_atomic justs saves the gamma lut for later. However,
>>>> it saves it to the gamma_store which should already be up to date with what
>>>> .gamma_get would return and is thus a nop. So, zap it.
>>>
>>> Removing drm_fb_helper_save_lut_atomic should be a separate patch I
>>> think.
>>
>> Then 3 patches would be needed, first some hybrid thing that does it the
>> old way, but also stores the lut in .gamma_store, then the split-out that
>> removes drm_fb_helper_save_lut_atomic, then whatever is needed to get
>> to the desired code. I can certainly do that, but do you want me to?
>
> Explain that in the commit message and it's fine.
I did the split in v2, I assume that's ok too. Better in case anyone ever
needs to run a bisect on this...
>>> It's a pre-existing bug, but should we also try to restore the fbdev lut
>>> in drm_fb_helper_restore_fbdev_mode_unlocked()? Would be yet another bug,
>>> but might be relevant for your use-case. Just try to run both an fbdev
>>> application and some kms-native thing, and then SIGKILL the native kms
>>> app.
>>>
>>> But since pre-existing not really required, and probably too much effort.
>>
>> Good thing too, because I don't really know my way around this code...
>
> Btw I cc'ed you on one of my patches in the fbdev locking series, we might
> need to do the same legacy vs. atomic split for the new lut code as I did
> for dpms. The rule with atomic is that you can't do multiple commits under
> drm_modeset_lock_all, you either have to do one overall atomic commit
> (preferred) or drop&reacquire locks again. This matters for LUT since
> you're updating the LUT on all CRTCs, which when using the gamma_set
> atomic helper would be multiple commits :-/
Ahh, ok, I see the problem.
> Using the dpms patch as template it shouldn't be too hard to address that
> for your patch here too.
Hmm, in that patch you handle the legacy case in a separate function, and
doing that for the lut case looks difficult when the atomic commit happens
inside the helper (typically drm_atomic_helper_legacy_gamma_set which
could perhaps be handled, but a real drag to handle for drivers that have
a custom crtc .gamma_set).
So, I'm aiming for the drop&reacquire approach...
However, I don't have all of that series, and I suspect that is why I do
not have any fb_helper->lock.
I'll send my best guess as a follow-up to patch 3/14 in v2.
Cheers,
peda
next prev parent reply other threads:[~2017-06-22 8:48 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-20 19:25 [PATCH 00/11] improve the fb_setcmap helper Peter Rosin
2017-06-20 19:25 ` [PATCH 01/11] drm/fb-helper: do a generic fb_setcmap helper in terms of crtc .gamma_set Peter Rosin
2017-06-21 7:38 ` Daniel Vetter
2017-06-21 7:59 ` Michel Dänzer
2017-06-21 8:14 ` [Nouveau] " Daniel Vetter
2017-06-21 8:36 ` Michel Dänzer
2017-06-21 9:40 ` Peter Rosin
2017-06-22 6:36 ` Daniel Vetter
2017-06-22 8:48 ` Peter Rosin [this message]
2017-06-23 8:40 ` Daniel Vetter
2017-06-20 19:25 ` [PATCH 02/11] drm: amd: remove dead code and pointless local lut storage Peter Rosin
2017-06-20 19:25 ` [PATCH 03/11] drm: ast: " Peter Rosin
2017-06-20 19:25 ` [PATCH 04/11] drm: cirrus: " Peter Rosin
2017-06-20 19:25 ` [PATCH 05/11] dmr: gma500: " Peter Rosin
2017-06-20 19:25 ` [PATCH 06/11] drm: i915: " Peter Rosin
2017-06-20 19:25 ` [PATCH 07/11] drm: mgag200: " Peter Rosin
2017-06-20 19:25 ` [PATCH 08/11] drm: nouveau: " Peter Rosin
2017-06-21 10:35 ` Peter Rosin
2017-06-20 19:25 ` [PATCH 09/11] drm: radeon: " Peter Rosin
2017-06-20 19:25 ` [PATCH 10/11] drm: stm: " Peter Rosin
2017-06-20 19:25 ` [PATCH 11/11] drm: remove unused and redundant callbacks Peter Rosin
2017-06-21 16:34 ` kbuild test robot
2017-06-22 6:37 ` Daniel Vetter
2017-06-22 7:13 ` Boris Brezillon
2017-06-21 7:40 ` [PATCH 00/11] improve the fb_setcmap helper Daniel Vetter
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