Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933117AbdGKPMr (ORCPT ); Tue, 11 Jul 2017 11:12:47 -0400 Received: from mail-qk0-f178.google.com ([209.85.220.178]:33289 "EHLO mail-qk0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932229AbdGKPMp (ORCPT ); Tue, 11 Jul 2017 11:12:45 -0400 MIME-Version: 1.0 X-Originating-IP: [2a02:168:5640:0:960b:2678:e223:c1c6] In-Reply-To: References: <1499719682-31750-1-git-send-email-john.stultz@linaro.org> <20170710211833.bprcrq5tfpzxtpeg@art_vandelay> <20170711075625.peykmamxkt7slqdz@phenom.ffwll.local> From: Daniel Vetter Date: Tue, 11 Jul 2017 17:12:44 +0200 X-Google-Sender-Auth: OM-dCsa8s4N4nGe0hFrAcOAhLZ4 Message-ID: Subject: Re: [RFC][PATCH] drm: kirin: Restrict modes to known good mode clocks To: John Stultz Cc: Sean Paul , Jose Abreu , Chen Feng , lkml , Xinliang Liu , "dri-devel@lists.freedesktop.org" , Rongrong Zou , Daniel Vetter , Xinwei Kong Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1981 Lines: 40 On Tue, Jul 11, 2017 at 5:05 PM, John Stultz wrote: >>> > be even better if you could calculate whether the mode is valid, but I didn't >>> > spend enough time to figure out if this is possible. >>> >>> Theoretically that might be possible, checking if the requested freq >>> matches the calculated freq, and I've tried that but so far I've not >>> been able to get it to work, as in some cases the freq on the current >>> whitelist don't exactly match but do work on the large majority of >>> monitors tested (while other freq have a similar error but don't work >>> on most monitors). >>> >>> I'd like to spend some more time to try to refine and tune this, but >>> having the current whitelist works fairly well, so I'm not sure its >>> worth sitting on (this is basically the last functional patch >>> outstanding for HiKey to fully work upstream - except the mali gpu of >>> course), while I try to tinker and tune it. >>> >>> Thanks so much for the feedback! >> >> Yeah the proper approach is to compute your pll/clock settings and bail >> out if those don't work. That's generally a magic spreadsheet supplied by >> the hw validation engineers, and I honestly don't want to know how they >> create it. Explicit modelist in the kernel sounds like a very bad hack. > > So without such a magic spreadsheet, how would you suggest I move this forward? > Not having the whitelist hack and picking modes the device can't > generate is a fairly major usability issue. I guess if the whitelist is the only thing I'd do 2 things differently: - Whitelist the clocks, not modes, since that's what seems to matter here. - Put it as close as possible to the code that comuptes the clock settings (yet if you use the clock subsystem that's a bit hard, but for an atomic driver this should be where this is done ...). Whitelist of modes looks super-hacky. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch