From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38E98C3DA79 for ; Thu, 29 Dec 2022 09:23:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229988AbiL2JXm (ORCPT ); Thu, 29 Dec 2022 04:23:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229919AbiL2JXY (ORCPT ); Thu, 29 Dec 2022 04:23:24 -0500 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7DF86F593; Thu, 29 Dec 2022 01:23:23 -0800 (PST) X-IronPort-AV: E=McAfee;i="6500,9779,10574"; a="322250641" X-IronPort-AV: E=Sophos;i="5.96,283,1665471600"; d="scan'208";a="322250641" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Dec 2022 01:23:23 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10574"; a="742253680" X-IronPort-AV: E=Sophos;i="5.96,283,1665471600"; d="scan'208";a="742253680" Received: from smile.fi.intel.com ([10.237.72.54]) by FMSMGA003.fm.intel.com with ESMTP; 29 Dec 2022 01:23:19 -0800 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1pAp89-001455-1j; Thu, 29 Dec 2022 11:23:17 +0200 Date: Thu, 29 Dec 2022 11:23:17 +0200 From: Andy Shevchenko To: Binbin Zhou Cc: Binbin Zhou , Wolfram Sang , Wolfram Sang , Mika Westerberg , linux-i2c@vger.kernel.org, loongarch@lists.linux.dev, devicetree@vger.kernel.org, Huacai Chen , WANG Xuerui , Arnd Bergmann , Rob Herring , Krzysztof Kozlowski , Jianmin Lv Subject: Re: [PATCH V8 3/4] i2c: ls2x: Add driver for Loongson-2K/LS7A I2C controller Message-ID: References: <9d3e4997519fd9ecebae6fd241148cc22d3fe04f.1671688961.git.zhoubinbin@loongson.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Thu, Dec 29, 2022 at 11:20:01AM +0200, Andy Shevchenko wrote: > On Thu, Dec 29, 2022 at 03:31:47PM +0800, Binbin Zhou wrote: > > On Wed, Dec 28, 2022 at 5:57 AM Andy Shevchenko wrote: > > > On Fri, Dec 23, 2022 at 05:00:51PM +0800, Binbin Zhou wrote: ... > > > > +static int ls2x_i2c_xfer_one(struct ls2x_i2c_priv *priv, > > > > + struct i2c_msg *msg, bool stop) > > > > +{ > > > > + int ret; > > > > + bool is_read = msg->flags & I2C_M_RD; > > > > + > > > > + /* Contains steps to send start condition and address */ > > > > + ret = ls2x_i2c_start(priv, msg); > > > > + if (!ret) { > > > > + if (is_read) > > > > + ret = ls2x_i2c_rx(priv, msg->buf, msg->len); > > > > + else > > > > + ret = ls2x_i2c_tx(priv, msg->buf, msg->len); > > > > + > > > > + if (!ret && stop) > > > > + ret = ls2x_i2c_stop(priv); > > > > + } > > > > + > > > > + if (ret == -ENXIO) > > > > + ls2x_i2c_stop(priv); > > > > + else if (ret < 0) > > > > + ls2x_i2c_init(priv); > > > > + > > > > + return ret; > > > > +} > > > > > > Still this code is odd from reader's perspective. It's in particular not clear > > > if the stop can be called twice in a row. I recommend to split it to two > > > > Sorry, > > Actually, I don't quite understand why you keep thinking that the stop > > can be called twice in a row. > > Because nothing in the code suggests otherwise. You need deeply understand > the flow to ensure that it won't. This means that the code is fragile and > needs refactoring (even comment, which you can do a least won't help, because > changing code in the other parts may break all this and you won't notice it). > > > As I said in my last email, the logic here should be: > > In the first case, stop is called when the last msg is transmitted successfully; > > In the second case, stop is called when there is a NOACK during the > > transmission; > > In the third case, init is called when other errors occur during the > > transmission, such as TIMEOUT. > > > > The key pointer is the stop function will only return a TIMEOUT error > > or 0 for success, so if the stop function above is failed, the stop > > function below will never be called twice. > > > > Anyway, I also admit that this part of the code may not be concise and > > clear enough, and I have tried the following changes: > > > > 1. put the start function into the rx/tx function respectively. As followers: > > > > @@ -177,10 +177,16 @@ static int ls2x_i2c_start(struct ls2x_i2c_priv > > *priv, struct i2c_msg *msgs) > > return ls2x_i2c_send_byte(priv, LS2X_CR_START | LS2X_CR_WRITE); > > } > > > > -static int ls2x_i2c_rx(struct ls2x_i2c_priv *priv, u8 *buf, u16 len) > > +static int ls2x_i2c_rx(struct ls2x_i2c_priv *priv, struct i2c_msg *msg) > > { > > int ret; > > - u8 rxdata; > > + u8 rxdata, *buf = msg->buf; > > + u16 len = msg->len; > > + > > + /* Contains steps to send start condition and address */ > > + ret = ls2x_i2c_start(priv, msg); > > + if (ret) > > + return ret; > > > > while (len--) { > > ret = ls2x_i2c_xfer_byte(priv, > > @@ -195,9 +201,16 @@ static int ls2x_i2c_rx(struct ls2x_i2c_priv > > *priv, u8 *buf, u16 len) > > return 0; > > } > > > > -static int ls2x_i2c_tx(struct ls2x_i2c_priv *priv, u8 *buf, u16 len) > > +static int ls2x_i2c_tx(struct ls2x_i2c_priv *priv, struct i2c_msg *msg) > > { > > int ret; > > + u8 *buf = msg->buf; > > + u16 len = msg->len; > > + > > + /* Contains steps to send start condition and address */ > > + ret = ls2x_i2c_start(priv, msg); > > + if (ret) > > + return ret; > > > > while (len--) { > > writeb(*buf++, priv->base + I2C_LS2X_TXR); > > > > 2. define the variable 'reinit' in the xfer_one function to mark the > > cases where reinit is needed. As follows: > > > > static int ls2x_i2c_xfer_one(struct ls2x_i2c_priv *priv, > > struct i2c_msg *msg, bool stop) > > { > > int ret, ret2; > > bool reinit = false; > > bool is_read = msg->flags & I2C_M_RD; > > > > if (is_read) > > ret = ls2x_i2c_rx(priv, msg); > > else > > ret = ls2x_i2c_tx(priv, msg); > > > > if (ret == -EAGAIN) /* could not acquire bus. bail out without STOP */ > > return ret; > > > > if (ret == -ETIMEDOUT) { > > /* Fatal error. Needs reinit. */ > > stop = false; > > reinit = true; Why do you need to initialize stop here? Why not to call reinit here and bailout? > > } > > > > if (stop) { > > ret2 = ls2x_i2c_stop(priv); > > > > if (ret2) { > > /* Failed to issue STOP. Needs reinit. */ > > reinit = true; > > ret = ret ?: ret2; All the same, try to be less verbose with unneeded variables. > > } > > } > > > > if (reinit) > > ls2x_i2c_init(priv); > > > > return ret; > > } > > > > Do you think this is better? > > Slightly, but still twisted at the end with the play of error codes. Try to > make it even more clear. > > > > functions and then do something like > > > > > > _read_one() > > > { > > > ret = start(); > > > if (ret) > > > goto _stop; // Do we really need this? > > > > > > ret = rx(); > > > if (ret) > > > goto _stop; // Do we need this? > > > > > > /* By setting this call the stop */ > > > if (stop) > > > ret = -ENXIO; > > > > > > out_send_stop: > > > if (ret == ...) > > > return _stop(); > > > // I don't like above, so this error checking/setting parts > > > // also can be rethought and refactored accordingly > > > > > > return ret; > > > } > > > > > > > > > if (is_read) > > > ret = _read_one(); > > > else > > > ret = _write_one(); > > > > > > if (ret) > > > _init(); > > > > > > return ret; -- With Best Regards, Andy Shevchenko