Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759749Ab3EFXFG (ORCPT ); Mon, 6 May 2013 19:05:06 -0400 Received: from mail-qc0-f175.google.com ([209.85.216.175]:54063 "EHLO mail-qc0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757754Ab3EFXFB (ORCPT ); Mon, 6 May 2013 19:05:01 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 6 May 2013 19:04:59 -0400 Message-ID: Subject: Re: [PATCH 3/7] drm: Update drm_addmap and drm_mmap to use PAT WC instead of MTRRs From: Jerome Glisse To: Andy Lutomirski Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1559 Lines: 35 On Mon, May 6, 2013 at 5:22 PM, Andy Lutomirski wrote: > On Fri, May 3, 2013 at 4:00 PM, Andy Lutomirski wrote: >> Signed-off-by: Andy Lutomirski >> --- >> >> This needs careful review. I don't really know what this code does, nor >> do I have the hardware. (I don't understand AGP and the associated >> caching implications.) > > This patch is wrong (I didn't update the matching mtrr_del), and I'm > reworking this whole series. But I may need some help on this one: > why is the mtrr handle of a map (whatever a map is) exported to > userspace via the ADD_MAP and GET_MAP ioctls? What (if anything) is > userspace supposed to do with it? Do I need to return a valid MTRR > register number? Is there any userspace code at all that sets > _DRM_WRITE_COMBINING in DRM_IOCTL_ADD_MAP with appropriate alignment > and needs the MTRR, for which the drm driver doesn't already add the > MTRR? > > --Andy >From memory, even on pat system we need mtrr for VRAM is PCI BAR. We cover it with a write combine MTRR. The whole ioctl is use by some ddx or maybe even directly the XServer to do this mtrr mess in userspace. Sorry for the bad news, but that's what i remember on that front thought i would need to read all the code again. Cheers, Jerome -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/