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Tue, 19 Jan 2021 00:35:22 -0800 (PST) Date: Tue, 19 Jan 2021 10:35:10 +0200 From: Pekka Paalanen To: Aurabindo Pillai Subject: Re: [PATCH v3 1/3] drm/amd/display: Add module parameter for freesync video mode Message-ID: <20210119103510.01f55ee4@eldfell> In-Reply-To: References: <20210104210800.789944-1-aurabindo.pillai@amd.com> <20210104210800.789944-2-aurabindo.pillai@amd.com> <20210114111445.1d2bbf62@eldfell> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: stylon.wang@amd.com, shashank.sharma@amd.com, thong.thai@amd.com, dri-devel@lists.freedesktop.org, Christian =?UTF-8?B?S8O2bmln?= , amd-gfx@lists.freedesktop.org, Daniel Vetter , wayne.lin@amd.com, alexander.deucher@amd.com, nicholas.kazlauskas@amd.com Content-Type: multipart/mixed; boundary="===============0354097954==" Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" --===============0354097954== Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/fAfjNpz1Akj+iHvP1bdqmi5"; protocol="application/pgp-signature" --Sig_/fAfjNpz1Akj+iHvP1bdqmi5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Mon, 18 Jan 2021 09:36:47 -0500 Aurabindo Pillai wrote: > On Thu, 2021-01-14 at 11:14 +0200, Pekka Paalanen wrote: > >=20 > > Hi, > >=20 > > please document somewhere that ends up in git history (commit > > message, > > code comments, description of the parameter would be the best but > > maybe > > there isn't enough space?) what Christian K=C3=B6nig explained in > >=20 > > =20 > > https://lists.freedesktop.org/archives/dri-devel/2020-December/291254.h= tml > >=20 > > that this is a stop-gap feature intended to be removed as soon as > > possible (when a better solution comes up, which could be years). > >=20 > > So far I have not seen a single mention of this intention in your > > patch > > submissions, and I think it is very important to make known. =20 >=20 > Hi, >=20 > Thanks for the headsup, I shall add the relevant info in the next > verison. >=20 > >=20 > > I also did not see an explanation of why this instead of > > manufacturing > > these video modes in userspace (an idea mentioned by Christian in the > > referenced email). I think that too should be part of a commit > > message. =20 >=20 > This is an opt-in feature, which shall be superseded by a better > solution. We also add a set of common modes for scaling similarly. > Userspace can still add whatever mode they want. So I dont see a reason > why this cant be in the kernel. Hi, sorry, I think that kind of thinking is backwards. There needs to be a reason to put something in the kernel, and if there is no reason, then it remains in userspace. So what's the reason to put this in the kernel? One example reason why this should not be in the kernel is that the set of video modes to manufacture is a kind of policy, which modes to add and which not. Userspace knows what modes it needs, and establishing the modes in the kernel instead is second-guessing what the userspace would want. So if userspace needs to manufacture modes in userspace anyway as some modes might be missed by the kernel, then why bother in the kernel to begin with? Why should the kernel play catch-up with what modes userspace wants when we already have everything userspace needs to make its own modes, even to add them to the kernel mode list? Does manufacturing these extra video modes to achieve fast timing changes require AMD hardware-specific knowledge, as opposed to the general VRR approach of simply adjusting the front porch? Something like this should also be documented in a commit message. Or if you insist that "no reason to not put this in the kernel" is reason enough, then write that down, because it does not seem obvious to me or others that this feature needs to be in the kernel. Thanks, pq --Sig_/fAfjNpz1Akj+iHvP1bdqmi5 Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEJQjwWQChkWOYOIONI1/ltBGqqqcFAmAGmb4ACgkQI1/ltBGq qqeshQ//W0890n+Hwi29RgSXln6rBJKoJhk5yWxXaS30OpE7indW26U+A/c1bNJf Mnh85h6Zrg6J66bdHgESUi/cA+303/r56myUjEa89mAvHxcDszyZS3a8fQs9x+Yv 5QCnML3PdTS6sbyg4JdqpXXSGIkM7OgYgEIaHf7bw7nKngSxUjhf+Ms+Kdf+AOGp tU6+lrNZzLkEEbjAW+eEf+cnLMkCOaPrTGtXw/2b4fe2MUhXqLL7LarVUMMuLQRZ HjJKqNUZ3ATM4oczTGf3k1u3pXwk3lN7Idgc6T0A1nzJJJluJRkMpV8c6kSJCtS2 CFpwaVr+GH9GFHBwzLuQY8hBdzRSqzIGAbc8tHFQwPcGe5a61SB4KbAuA62FliY/ VVYLf44njwzeALhRnlORdWvobjD3BT9oMGBtqvev7+EjjLTzsFQ3WlavUMlmU3Di kbFcAbM2hRFAWRzcFI50mRXRs3wy0TuGzah9P+zzg43hdclmyTp/1lRfEQZ6kWJX BzzgRUVYNLBOHGma5pY63q/VDpnNg2wdDYU1PgZZRK5P9F0j7zfq4/KsGNuaAiaQ 37YUXuNnj/p7kDjHx27dwKmlogmGLM2D3wx22S7IAkEZWIESKPKKa2kSjQvVzfCH AlhuHOvyoFwBj4BzbfPc2nkSNbJdyZ2qztKnUC8OCEZBb8y6LyE= =vt/2 -----END PGP SIGNATURE----- --Sig_/fAfjNpz1Akj+iHvP1bdqmi5-- --===============0354097954== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx --===============0354097954==--