From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw1-f71.google.com (mail-yw1-f71.google.com [209.85.161.71]) by kanga.kvack.org (Postfix) with ESMTP id A97A76B61F3 for ; Sun, 2 Dec 2018 01:11:15 -0500 (EST) Received: by mail-yw1-f71.google.com with SMTP id p141so1988096ywg.17 for ; Sat, 01 Dec 2018 22:11:15 -0800 (PST) Received: from gate.crashing.org (gate.crashing.org. [63.228.1.57]) by mx.google.com with ESMTPS id a93-v6si6119636ybi.258.2018.12.01.22.11.14 for (version=TLS1 cipher=AES128-SHA bits=128/128); Sat, 01 Dec 2018 22:11:14 -0800 (PST) Message-ID: <42b1408cafe77ebac1b1ad909db237fe34e4d177.camel@kernel.crashing.org> Subject: Re: use generic DMA mapping code in powerpc V4 From: Benjamin Herrenschmidt Date: Sun, 02 Dec 2018 17:11:02 +1100 In-Reply-To: References: <20181130103222.GA23393@lst.de> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rui Salvaterra , hch@lst.de Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org On Fri, 2018-11-30 at 11:44 +0000, Rui Salvaterra wrote: > Thanks for the quick response! I applied it on top of your > powerpc-dma.4 branch and retested. > I'm not seeing nouveau complaining anymore (I'm not using X11 or any > DE, though). > In any case and FWIW, this series is > > Tested-by: Rui Salvaterra Talking of which ... Christoph, not sure if we can do something about this at the DMA API level or keep hacks but some adapters such as the nVidia GPUs have a HW hack we can use to work around their limitations in that case. They have a register that can program a fixed value for the top bits that they don't support. This works fine for any linear mapping with an offset, provided they can program the offset in that register and they have enough DMA range to cover all memory from that offset. I can probably get the info about this from them so we can exploit it in nouveau. Cheers, Ben. > Thanks, > Rui