From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Date: Thu, 08 Dec 2016 21:23:30 +0000 Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers Message-Id: <1481232210.26959.47.camel@kernel.crashing.org> List-Id: References: <1479888193-23908-1-git-send-email-tomi.valkeinen@ti.com> <1481158879.26959.41.camel@kernel.crashing.org> <035da7a8-5a3f-1ef6-f686-479773e78084@ti.com> In-Reply-To: <035da7a8-5a3f-1ef6-f686-479773e78084@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tomi Valkeinen , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Greg Kroah-Hartman , Thomas Petazzoni , Noralf =?ISO-8859-1?Q?Tr=F8nnes?= , Sudip Mukherjee , Teddy Wang , Arnaud Patard , airlied@linux.ie Cc: linux-kernel@vger.kernel.org On Thu, 2016-12-08 at 10:01 +0200, Tomi Valkeinen wrote: > > > DRM drivers don't strike me as suitable for small/slow cores with dumb > > framebuffers or simple 2D only accel, such as the one found in the ASpeed > > BMCs. > > Then the DRM framework should be improved to be suitable. Dave ? :-) > > With drmfb you basically have to shadow everything into memory & copy > > over everything, and locks you out of simple 2D accel. For a simple text > > console the result is orders of magnitude slower and memory hungry than > > a simple fbdev. > > I don't think that's true. You can have a single fbdev buffer and blit > there all you want, afaik. Well, I had that argument with Dave Airlie which I CCed. The "dumb" ones like bochsdrmfb, cirrusdrmfb, astdrmfb ... all use shadowing, meaning they use a lot more memory and cannot do any 2D acceleration for fbcon. >From memory, David claimed you cannot directly work on the fb with a "proper" DRM driver. Maybe I misunderstood but then the DRM shines by its complete absence of useful documentation mixed with bazillion layers of APIs and helpers so it's pretty hard to get ones head around it without wasting very large amounts of time which I don't have at the moment. > > Not everything has a powerful 3D GPU. > > We don't use GPU on OMAPs (except for 3D). The CPU in an OMAP is order of magnitude faster than what I have in an Aspeed BMC though. Ben. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers Date: Fri, 09 Dec 2016 08:23:30 +1100 Message-ID: <1481232210.26959.47.camel@kernel.crashing.org> References: <1479888193-23908-1-git-send-email-tomi.valkeinen@ti.com> <1481158879.26959.41.camel@kernel.crashing.org> <035da7a8-5a3f-1ef6-f686-479773e78084@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3476F6E85C for ; Thu, 8 Dec 2016 21:23:50 +0000 (UTC) In-Reply-To: <035da7a8-5a3f-1ef6-f686-479773e78084@ti.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Tomi Valkeinen , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Greg Kroah-Hartman , Thomas Petazzoni , Noralf =?ISO-8859-1?Q?Tr=F8nnes?= , Sudip Mukherjee , Teddy Wang , Arnaud Patard , airlied@linux.ie Cc: linux-kernel@vger.kernel.org List-Id: dri-devel@lists.freedesktop.org T24gVGh1LCAyMDE2LTEyLTA4IGF0IDEwOjAxICswMjAwLCBUb21pIFZhbGtlaW5lbiB3cm90ZToK PiAKPiA+IERSTSBkcml2ZXJzIGRvbid0IHN0cmlrZSBtZSBhcyBzdWl0YWJsZSBmb3Igc21hbGwv c2xvdyBjb3JlcyB3aXRoIGR1bWIKPiA+IGZyYW1lYnVmZmVycyBvciBzaW1wbGUgMkQgb25seSBh Y2NlbCwgc3VjaCBhcyB0aGUgb25lIGZvdW5kIGluIHRoZSBBU3BlZWQKPiA+IEJNQ3MuCj4gCj4g VGhlbiB0aGUgRFJNIGZyYW1ld29yayBzaG91bGQgYmUgaW1wcm92ZWQgdG8gYmUgc3VpdGFibGUu CgpEYXZlID8gOi0pCgo+ID4gV2l0aCBkcm1mYiB5b3UgYmFzaWNhbGx5IGhhdmUgdG8gc2hhZG93 IGV2ZXJ5dGhpbmcgaW50byBtZW1vcnkgJiBjb3B5Cj4gPiBvdmVyIGV2ZXJ5dGhpbmcsIGFuZCBs b2NrcyB5b3Ugb3V0IG9mIHNpbXBsZSAyRCBhY2NlbC4gRm9yIGEgc2ltcGxlIHRleHQKPiA+IGNv bnNvbGUgdGhlIHJlc3VsdCBpcyBvcmRlcnMgb2YgbWFnbml0dWRlIHNsb3dlciBhbmQgbWVtb3J5 IGh1bmdyeSB0aGFuCj4gPiBhIHNpbXBsZSBmYmRldi4KPiAKPiBJIGRvbid0IHRoaW5rIHRoYXQn cyB0cnVlLiBZb3UgY2FuIGhhdmUgYSBzaW5nbGUgZmJkZXYgYnVmZmVyIGFuZCBibGl0Cj4gdGhl cmUgYWxsIHlvdSB3YW50LCBhZmFpay4KCldlbGwsIEkgaGFkIHRoYXQgYXJndW1lbnQgd2l0aCBE YXZlIEFpcmxpZSB3aGljaCBJIENDZWQuIFRoZSAiZHVtYiIgb25lcyBsaWtlCmJvY2hzZHJtZmIs IGNpcnJ1c2RybWZiLCBhc3Rkcm1mYiAuLi4gYWxsIHVzZSBzaGFkb3dpbmcsIG1lYW5pbmcgdGhl eSB1c2UgYQpsb3QgbW9yZSBtZW1vcnkgYW5kIGNhbm5vdCBkbyBhbnkgMkQgYWNjZWxlcmF0aW9u IGZvciBmYmNvbi4KCkZyb20gbWVtb3J5LCBEYXZpZCBjbGFpbWVkIHlvdSBjYW5ub3QgZGlyZWN0 bHkgd29yayBvbiB0aGUgZmIgd2l0aCBhICJwcm9wZXIiCkRSTSBkcml2ZXIuIE1heWJlIEkgbWlz dW5kZXJzdG9vZCBidXQgdGhlbiB0aGUgRFJNIHNoaW5lcyBieSBpdHMgY29tcGxldGUKYWJzZW5j ZSBvZiB1c2VmdWwgZG9jdW1lbnRhdGlvbiBtaXhlZCB3aXRoIGJhemlsbGlvbiBsYXllcnMgb2Yg QVBJcyBhbmQgaGVscGVycwpzbyBpdCdzIHByZXR0eSBoYXJkIHRvIGdldCBvbmVzIGhlYWQgYXJv dW5kIGl0IHdpdGhvdXQgd2FzdGluZyB2ZXJ5IGxhcmdlIGFtb3VudHMKb2YgdGltZSB3aGljaCBJ IGRvbid0IGhhdmUgYXQgdGhlIG1vbWVudC4KCj4gPiBOb3QgZXZlcnl0aGluZyBoYXMgYSBwb3dl cmZ1bCAzRCBHUFUuCj4gCj4gV2UgZG9uJ3QgdXNlIEdQVSBvbiBPTUFQcyAoZXhjZXB0IGZvciAz RCkuCgpUaGUgQ1BVIGluIGFuIE9NQVAgaXMgb3JkZXIgb2YgbWFnbml0dWRlIGZhc3RlciB0aGFu IHdoYXQgSSBoYXZlIGluIGFuCkFzcGVlZCBCTUMgdGhvdWdoLgoKQmVuLgoKX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRldmVsIG1haWxpbmcgbGlz dApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBzOi8vbGlzdHMuZnJlZWRlc2t0 b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVsCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932691AbcLHVYP (ORCPT ); Thu, 8 Dec 2016 16:24:15 -0500 Received: from gate.crashing.org ([63.228.1.57]:49730 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753391AbcLHVYO (ORCPT ); Thu, 8 Dec 2016 16:24:14 -0500 Message-ID: <1481232210.26959.47.camel@kernel.crashing.org> Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers From: Benjamin Herrenschmidt To: Tomi Valkeinen , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Greg Kroah-Hartman , Thomas Petazzoni , Noralf =?ISO-8859-1?Q?Tr=F8nnes?= , Sudip Mukherjee , Teddy Wang , Arnaud Patard , airlied@linux.ie Cc: linux-kernel@vger.kernel.org Date: Fri, 09 Dec 2016 08:23:30 +1100 In-Reply-To: <035da7a8-5a3f-1ef6-f686-479773e78084@ti.com> References: <1479888193-23908-1-git-send-email-tomi.valkeinen@ti.com> <1481158879.26959.41.camel@kernel.crashing.org> <035da7a8-5a3f-1ef6-f686-479773e78084@ti.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.2 (3.22.2-1.fc25) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2016-12-08 at 10:01 +0200, Tomi Valkeinen wrote: > > > DRM drivers don't strike me as suitable for small/slow cores with dumb > > framebuffers or simple 2D only accel, such as the one found in the ASpeed > > BMCs. > > Then the DRM framework should be improved to be suitable. Dave ? :-) > > With drmfb you basically have to shadow everything into memory & copy > > over everything, and locks you out of simple 2D accel. For a simple text > > console the result is orders of magnitude slower and memory hungry than > > a simple fbdev. > > I don't think that's true. You can have a single fbdev buffer and blit > there all you want, afaik. Well, I had that argument with Dave Airlie which I CCed. The "dumb" ones like bochsdrmfb, cirrusdrmfb, astdrmfb ... all use shadowing, meaning they use a lot more memory and cannot do any 2D acceleration for fbcon. >>From memory, David claimed you cannot directly work on the fb with a "proper" DRM driver. Maybe I misunderstood but then the DRM shines by its complete absence of useful documentation mixed with bazillion layers of APIs and helpers so it's pretty hard to get ones head around it without wasting very large amounts of time which I don't have at the moment. > > Not everything has a powerful 3D GPU. > > We don't use GPU on OMAPs (except for 3D). The CPU in an OMAP is order of magnitude faster than what I have in an Aspeed BMC though. Ben.