From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [RFC PATCH 2/4] pio-mapping: Add ARM support for the PIO mapping API Date: Thu, 18 Feb 2010 07:39:39 +1100 Message-ID: <1266439179.16346.287.camel@pasglop> References: <20100205163044.30827.10915.stgit@pc1117.cambridge.arm.com> <20100205163154.30827.6636.stgit@pc1117.cambridge.arm.com> <1265388234.14404.47.camel@mulgrave.site> <1265390403.7692.101.camel@pc1117.cambridge.arm.com> <1265391384.14404.53.camel@mulgrave.site> <1265645421.4020.119.camel@pc1117.cambridge.arm.com> <1265649274.6289.12.camel@mulgrave.site> <1265738604.8655.58.camel@pc1117.cambridge.arm.com> <1266397895.16346.267.camel@pasglop> <20100217200445.GA29249@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from gate.crashing.org ([63.228.1.57]:36514 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756020Ab0BQUo6 (ORCPT ); Wed, 17 Feb 2010 15:44:58 -0500 In-Reply-To: <20100217200445.GA29249@flint.arm.linux.org.uk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Russell King Cc: Catalin Marinas , James Bottomley , linux-arch@vger.kernel.org On Wed, 2010-02-17 at 20:04 +0000, Russell King wrote: > > That would be fine if we weren't already using PG_arch_1 for delaying > D-cache flushes for pages which aren't mapped, in the same way that > Sparc64 does. Interesting. Maybe we need more arch bits in there :-) > That doesn't cover this case though - the problem is not I/D cache > coherency - the problem has manifested itself as data corruption when > userspace reads the page. Yup, let's stick to the other thread. I still don't see why a PIO mapping API is needed, from what I've read so far, it's a case of mis-using the existing DMA API that could be fixed at the driver level. No ? Cheers, Ben.