Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751458AbaLQMfE (ORCPT ); Wed, 17 Dec 2014 07:35:04 -0500 Received: from mail-qg0-f48.google.com ([209.85.192.48]:59414 "EHLO mail-qg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750829AbaLQMfB (ORCPT ); Wed, 17 Dec 2014 07:35:01 -0500 MIME-Version: 1.0 In-Reply-To: <20141211145849.GH31456@e104818-lin.cambridge.arm.com> References: <1418266726-12004-1-git-send-email-a.kesavan@samsung.com> <1418266726-12004-2-git-send-email-a.kesavan@samsung.com> <1418292513.3188.4.camel@pengutronix.de> <20141211103919.GA6067@arm.com> <1418298046.3188.10.camel@pengutronix.de> <20141211145849.GH31456@e104818-lin.cambridge.arm.com> Date: Wed, 17 Dec 2014 18:05:00 +0530 Message-ID: Subject: Re: [PATCH 2/2] misc: sram: switch to ioremap_wc from ioremap From: Abhilash Kesavan To: Catalin Marinas Cc: Philipp Zabel , Will Deacon , Santosh Shilimkar , Tony Lindgren , "heiko@sntech.de" , "Li.Xiubo@freescale.com" , "shc_work@mail.ru" , "nicoleotsuka@gmail.com" , "arnd@arndb.de" , "gregkh@linuxfoundation.org" , "robh+dt@kernel.org" , "grant.likely@linaro.org" , "linux-kernel@vger.kernel.org" , "corbet@lwn.net" , "padma.v@samsung.com" , "alsa-devel@alsa-project.org" , "shawn.guo@freescale.com" , "bcousson@baylibre.com" , "kernel@pengutronix.de" , "kgene@kernel.org" , Pawel Moll Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Thu, Dec 11, 2014 at 8:28 PM, Catalin Marinas wrote: > On Thu, Dec 11, 2014 at 11:40:46AM +0000, Philipp Zabel wrote: >> Hi Will, >> >> Am Donnerstag, den 11.12.2014, 10:39 +0000 schrieb Will Deacon: >> > On Thu, Dec 11, 2014 at 10:08:33AM +0000, Philipp Zabel wrote: >> > > Hi Abhilash, >> > > >> > > Am Donnerstag, den 11.12.2014, 08:28 +0530 schrieb Abhilash Kesavan: >> > > > Currently, the SRAM allocator returns device memory via ioremap. >> > > > This causes issues on ARM64 when the internal SoC SRAM allocated by >> > > > the generic sram driver is used for audio playback. The destination >> > > > buffer address (which is ioremapped SRAM) is not 64-bit aligned for >> > > > certain streams (e.g. 44.1k sampling rate). In such cases we get >> > > > unhandled alignment faults. Use ioremap_wc in place of ioremap which >> > > > gives us normal non-cacheable memory instead of device memory. >> > > >> > > Could this break the omap_bus_sync() implementation in >> > > arch/arm/mach-omap2/omap4-common.c? >> > > >> > > void omap_bus_sync(void) >> > > { >> > > if (dram_sync && sram_sync) { >> > > writel_relaxed(readl_relaxed(dram_sync), dram_sync); >> > > writel_relaxed(readl_relaxed(sram_sync), sram_sync); >> > > isb(); >> > > } >> > > } >> > > >> > > It is used in wmb() and omap_do_wfi() to drain interconnect write >> > > buffers on omap4/5. If sram_sync is mapped with write-combining, could >> > > the last write to sram_sync stay stuck in the write-combining buffer >> > > until after the function returns? >> > >> > I think you have that issue anyway, since you can get an early write >> > response even if you use ioremap. Does the write to sram_sync have >> > side-effects that we need to wait for? >> >> [Added Tony Lindgren and Santosh Shilimkar to Cc:] >> I don't know. > > In addition to Will's question, do you care about the access size? > ioremap() returns Device memory which is bufferable (early > acknowledgement) but it guarantees the access size. With write > combining, you may get a different access size than requested. >From the existing dts files, omap, imx, rockchip and exynos seem to be the only users of the sram allocator code. I have tested this on Exynos5420, Exynos5800 and Exynos7; there is no change in behavior seen on these boards. Tested-by for other SoCs would be appreciated. Regards, Abhilash > > -- > Catalin -- 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/