Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752279AbbKIOZN (ORCPT ); Mon, 9 Nov 2015 09:25:13 -0500 Received: from mail-yk0-f178.google.com ([209.85.160.178]:36473 "EHLO mail-yk0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751168AbbKIOZK (ORCPT ); Mon, 9 Nov 2015 09:25:10 -0500 MIME-Version: 1.0 In-Reply-To: <1447047839-5223-2-git-send-email-liguo.zhang@mediatek.com> References: <1447047839-5223-1-git-send-email-liguo.zhang@mediatek.com> <1447047839-5223-2-git-send-email-liguo.zhang@mediatek.com> Date: Mon, 9 Nov 2015 16:25:09 +0200 Message-ID: Subject: Re: [PATCH v2 1/2] i2c: mediatek: add i2c first write then read optimization From: Andy Shevchenko To: Liguo Zhang Cc: Wolfram Sang , srv_heupstream@mediatek.com, Matthias Brugger , Eddie Huang , Xudong Chen , Sascha Hauer , linux-i2c@vger.kernel.org, "linux-kernel@vger.kernel.org" , linux-arm Mailing List , linux-mediatek@lists.infradead.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1286 Lines: 36 On Mon, Nov 9, 2015 at 7:43 AM, Liguo Zhang wrote: > For platform with auto restart support, between every transfer, > i2c controller will trigger an interrupt and SW need to handle > it to start new transfer. When doing write-then-read transfer, > instead of restart mechanism, using WRRD mode to have controller > send both transfer in one request to reduce latency. > @@ -518,6 +529,16 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap, > if (ret) > return ret; > > + i2c->auto_restart = i2c->dev_comp->auto_restart; > + > + /* checking if we can skip restart and optimize using WRRD mode */ > + if (i2c->auto_restart && num == 2) { > + if (!(msgs[0].flags & I2C_M_RD) && (msgs[1].flags & I2C_M_RD) && > + msgs[0].addr == msgs[1].addr) { Nitpick (optional): ((msgs[0].flags & msgs[1].flags) & I2C_M_RD) ? > + i2c->auto_restart = 0; > + } > + } -- With Best Regards, Andy Shevchenko -- 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/