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 0CA69C77B73 for ; Mon, 22 May 2023 14:59:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233502AbjEVO7Y (ORCPT ); Mon, 22 May 2023 10:59:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234207AbjEVO7S (ORCPT ); Mon, 22 May 2023 10:59:18 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F45A1AD; Mon, 22 May 2023 07:59:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1684767550; x=1716303550; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=eGWqhbY4zoCc+GFxYj9kerl8y0O3B0XglUVKZ8y8N3Q=; b=LPJbtx1MFUaBpvTQBD9RoFy8D5/Cls3Y4LF0FjCSpYUqgUWNLppEFykZ Lfnxfj/1C48SJgXlPx5AsqO+15JXtf05psVfnxty1YI5230SEMRjF94Cl zX5uhu9gBy6pX/7k8akzW8is2yNK8FlnuIEtypbNZ+1j1khTRI1ufXzB6 IAtivFoUfMm7u0QHNIKByQYEmtYlRDpWItBG1Gj2KARMiwZRTNkm1sxJS smuhABluAJyvuGWS+b3x/ZHnoeBBv4DuSJ/ivGg0FcSsxhyfp6p68n8+d qRgiPgeiXy1hCo/xGlfqNJJebgvHFWEFGKBSrd+vJL4eCgMDmI8hBqN6G g==; X-IronPort-AV: E=McAfee;i="6600,9927,10718"; a="342396097" X-IronPort-AV: E=Sophos;i="6.00,184,1681196400"; d="scan'208";a="342396097" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 May 2023 07:58:29 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10718"; a="703544278" X-IronPort-AV: E=Sophos;i="6.00,184,1681196400"; d="scan'208";a="703544278" Received: from mylly.fi.intel.com (HELO [10.237.72.160]) ([10.237.72.160]) by orsmga002.jf.intel.com with ESMTP; 22 May 2023 07:58:27 -0700 Message-ID: Date: Mon, 22 May 2023 17:58:26 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.10.0 Subject: Re: [PATCH] i2c: designware: fix idx_write_cnt in read loop Content-Language: en-US To: David Zheng , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Cc: andriy.shevchenko@linux.intel.com, mika.westerberg@linux.intel.com, jsd@semihalf.com References: From: Jarkko Nikula In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Hi On 5/18/23 21:06, David Zheng wrote: > With IC_INTR_RX_FULL slave interrupt handler reads data in a loop until > RX FIFO is empty. When testing with the slave-eeprom, each transaction > has 2 bytes for address/index and 1 byte for value, the address byte > can be written as data byte due to dropping STOP condition. > > In the test below, the master continuously writes to the slave, first 2 > bytes are index, 3rd byte is value and follow by a STOP condition. > > i2c_write: i2c-3 #0 a=04b f=0000 l=3 [00-D1-D1] > i2c_write: i2c-3 #0 a=04b f=0000 l=3 [00-D2-D2] > i2c_write: i2c-3 #0 a=04b f=0000 l=3 [00-D3-D3] > > Upon receiving STOP condition slave eeprom would reset `idx_write_cnt` so > next 2 bytes can be treated as buffer index for upcoming transaction. > Supposedly the slave eeprom buffer would be written as > > EEPROM[0x00D1] = 0xD1 > EEPROM[0x00D2] = 0xD2 > EEPROM[0x00D3] = 0xD3 > > When CPU load is high the slave irq handler may not read fast enough, > the interrupt status can be seen as 0x204 with both DW_IC_INTR_STOP_DET > (0x200) and DW_IC_INTR_RX_FULL (0x4) bits. The slave device may see > the transactions below. > > 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 > 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 > 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 > 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1794 : INTR_STAT=0x204 > 0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x1790 : INTR_STAT=0x200 > 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 > 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 > 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 > > After `D1` is received, read loop continues to read `00` which is the > first bype of next index. Since STOP condition is ignored by the loop, > eeprom buffer index increased to `D2` and `00` is written as value. > > So the slave eeprom buffer becomes > > EEPROM[0x00D1] = 0xD1 > EEPROM[0x00D2] = 0x00 > EEPROM[0x00D3] = 0xD3 > > The fix is to use `FIRST_DATA_BYTE` (bit 11) in `IC_DATA_CMD` to split > the transactions. The first index byte in this case would have bit 11 > set. Check this indication to inject I2C_SLAVE_WRITE_REQUESTED event > which will reset `idx_write_cnt` in slave eeprom. > > Signed-off-by: David Zheng > --- > drivers/i2c/busses/i2c-designware-core.h | 2 ++ > drivers/i2c/busses/i2c-designware-slave.c | 6 ++++-- > 2 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h > index c5d87aae39c6..8b85147bd518 100644 > --- a/drivers/i2c/busses/i2c-designware-core.h > +++ b/drivers/i2c/busses/i2c-designware-core.h > @@ -123,6 +123,8 @@ > #define DW_IC_COMP_PARAM_1_SPEED_MODE_HIGH (BIT(2) | BIT(3)) > #define DW_IC_COMP_PARAM_1_SPEED_MODE_MASK GENMASK(3, 2) > > +#define DW_IC_DATA_CMD_FIRST_DATA_BYTE BIT(11) > + > /* > * Sofware status flags > */ > diff --git a/drivers/i2c/busses/i2c-designware-slave.c b/drivers/i2c/busses/i2c-designware-slave.c > index cec25054bb24..9549cbcf50aa 100644 > --- a/drivers/i2c/busses/i2c-designware-slave.c > +++ b/drivers/i2c/busses/i2c-designware-slave.c > @@ -170,12 +170,14 @@ static irqreturn_t i2c_dw_isr_slave(int this_irq, void *dev_id) > if (!(dev->status & STATUS_WRITE_IN_PROGRESS)) { > dev->status |= STATUS_WRITE_IN_PROGRESS; > dev->status &= ~STATUS_READ_IN_PROGRESS; > - i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_REQUESTED, > - &val); > } > > do { > regmap_read(dev->map, DW_IC_DATA_CMD, &tmp); > + if (tmp & DW_IC_DATA_CMD_FIRST_DATA_BYTE) > + i2c_slave_event(dev->slave, > + I2C_SLAVE_WRITE_REQUESTED, > + &val); > val = tmp; > i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED, > &val); I fear this might cause regression on some use case on HW that doesn't have the FIRST_DATA_BYTE bit in IC_DATA_CMD. That is available on newer Synopsys I2C IPs only. For example my test HW doesn't have it. This means the I2C_SLAVE_WRITE_REQUESTED is never delivered on these HWs that don't implement the FIRST_DATA_BYTE. My quick tests using i2c-slave-eeprom didn't show regression but I'm sure there is a case that will regress because of that.