From mboxrd@z Thu Jan 1 00:00:00 1970 From: wsa@the-dreams.de (Wolfram Sang) Date: Tue, 13 Jan 2015 15:36:54 +0100 Subject: [PATCH] i2c: designware: use {readl|writel}_relaxed instead of readl/writel In-Reply-To: <1418279201-3886-1-git-send-email-jszhang@marvell.com> References: <1418279201-3886-1-git-send-email-jszhang@marvell.com> Message-ID: <20150113143654.GG7660@katana> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Dec 11, 2014 at 02:26:41PM +0800, Jisheng Zhang wrote: > readl/writel is too expensive especially on Cortex A9 w/ outer L2 cache. > This introduces i2c read/write errors on Marvell BG2/BG2Q SoCs when there > are heavy L2 cache maintenance operations at the same time. Reading this again, I got a question: Really read/write errors? I would think that there is a performance penalty because of the memory barriers. But errors? > The driver does not perform DMA, so it's safe to use the relaxed version. > From another side, the relaxed io accessor macros are available on all > architectures now, so we can use the relaxed versions instead. Can the designware core make use of DMA in theory? -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: