From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751068AbeC2HKb (ORCPT ); Thu, 29 Mar 2018 03:10:31 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:55798 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750707AbeC2HKa (ORCPT ); Thu, 29 Mar 2018 03:10:30 -0400 X-Google-Smtp-Source: AIpwx48FmUpaNgM/2c2vSEjSVI6BU7NwdIWx6a5QQM89fiJ+gtkh1iAfIRYZGIj05uSGePck+LzbEQ== Date: Thu, 29 Mar 2018 09:10:25 +0200 From: Daniel Vetter To: Boris Brezillon Cc: Daniel Vetter , Peter Rosin , Egbert Eich , Boris Brezillon , Alexandre Belloni , David Airlie , Nicolas Ferre , Takashi Iwai , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] drm/atmel-hlcdc: add command line option to specify preferred depth Message-ID: <20180329071025.GE3881@phenom.ffwll.local> Mail-Followup-To: Boris Brezillon , Peter Rosin , Egbert Eich , Boris Brezillon , Alexandre Belloni , David Airlie , Nicolas Ferre , Takashi Iwai , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20180326073502.19259-1-peda@axentia.se> <20180328093454.4149fa3b@bbrezillon> <20180328122236.GF14155@phenom.ffwll.local> <20180328142512.14f8c502@bbrezillon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180328142512.14f8c502@bbrezillon> X-Operating-System: Linux phenom 4.15.0-1-amd64 User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 28, 2018 at 02:25:12PM +0200, Boris Brezillon wrote: > On Wed, 28 Mar 2018 14:22:36 +0200 > Daniel Vetter wrote: > > > On Wed, Mar 28, 2018 at 09:34:54AM +0200, Boris Brezillon wrote: > > > Hi Peter, > > > > > > On Mon, 26 Mar 2018 09:35:02 +0200 > > > Peter Rosin wrote: > > > > > > > I have an sama5d31-based system with 64MB of memory and a 1920x1080 > > > > LVDS display wired for 16-bpp. When I enable legacy fbdev support, > > > > the contiguous memory allocator invariably fails with the order-11 > > > > allocation for a 1920x1080@24-bpp buffer (~6MB). But this HW can never > > > > make any good use of RGB888, so that is a wasted attempt anyway that > > > > would also waste precious memory should it succeed. > > > > > > > > Sure, I could rewrite user-space to go directly to KMS etc, and that > > > > makes the (attempted) order-11 allocation go away, replacing it with > > > > one order-10 allocation per application restart for a 1920x1080@16-bpp > > > > buffer (<4MB). But after a few restarts, order-10 allocations start to > > > > fail as well, which is only to be expected AFAIU. > > > > > > > > So, I'd rather not change user-space (which was originally written > > > > to target a smaller display) so that I at the same time get the > > > > benefit of an early pre-allocated fbdev frame-buffer that can be > > > > reused over and over. But to do that I need to tell the driver that > > > > 16-bpp is the preferred depth. Add a module parameter to do just that. > > > > > > > > Signed-off-by: Peter Rosin > > > > --- > > > > drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c | 18 +++++++++++++++++- > > > > 1 file changed, 17 insertions(+), 1 deletion(-) > > > > > > > > I found some inspiration regarding naming and implementation here: > > > > https://patchwork.kernel.org/patch/9848631/ > > > > > > > > I have found no feedback on that patch though, which makes me wonder if > > > > I'm perhaps barking up the wronig tree? > > > > > > Hm, isn't that something you can already overload with the video= > > > parameter? > > > > > > video=:[-] > > > > > > AFAIR, encodes the color depth, so what is the benefit of adding > > > this new property to overload the default depth? > > > > > > Maybe I'm wrong and the default depth param is actually useful, but in > > > this case we should probably make it generic since other drivers seems > > > to need it too, and we might want to attach it to a specific display > > > engine instance. > > > > I think for the drm's fbdev emulation we ignore the bpp ... > > Nope, it's already parsed [1]. > > [1]https://elixir.bootlin.com/linux/v4.16-rc3/source/drivers/gpu/drm/drm_fb_helper.c#L1812 Oh, totally missed this. I honestly wonder why we then have all the various bpp module options in different drivers ... -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch