Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 13 Mar 2001 21:49:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 13 Mar 2001 21:49:07 -0500 Received: from gherkin.sa.wlk.com ([192.158.254.49]:38156 "HELO gherkin.sa.wlk.com") by vger.kernel.org with SMTP id ; Tue, 13 Mar 2001 21:48:52 -0500 Message-Id: From: rct@gherkin.sa.wlk.com (Bob_Tracy) Subject: Re: another Cyrix/mtrr problem? In-Reply-To: "from davej@suse.de at Mar 14, 2001 00:20:21 am" To: davej@suse.de Date: Tue, 13 Mar 2001 20:48:02 -0600 (CST) CC: linux-kernel@vger.kernel.org X-Mailer: ELM [version 2.4ME+ PL82 (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org davej@suse.de wrote: > Normally the answer would be "Closed driver, complain to nVidia", > but just in case.. Glad you were open-minded enough to consider that it *might* be "our" code. > Can you verify that.. > > a. You have MTRR support compiled into the kernel. yes > b. You have a /proc/mtrr file yes > c. You can add/delete ranges using /proc/mtrr > (See Documentation/mtrr.txt for info on how to do this) yes, BUT... The "Documentation/mtrr.txt" file says "... 4 megabytes, which is 0x400000 bytes (in hexadecimal)." The math is correct: 1MB == 2**20 == 0x100000 the last time I checked. Unfortunately, when I execute echo "base=0xd8000000 size=0x100000 type=write-combining" >| /proc/mtrr I get a 2MB region instead of the 1MB region I expected... reg00: base=0xd8000000 (3456MB), size= 2MB: write-combining, count=1 reg01: base=0x000c0000 ( 0MB), size= 512KB: uncachable, count=1 reg07: base=0x00000000 ( 0MB), size= 256MB: write-through, count=1 Similarly, the NVIDIA driver attempts to create a 32MB write-combining region by passing a size argument of 0x2000000, and fails because the underlying mtrr code tries to carve out a 64MB region whereas my video card has only 32MB of RAM. Looks like an off-by-one (bit) error to me. So... Is this a legitimate bug sighting, or is my analysis faulty? --Bob Tracy rct@frus.com - 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/