From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756331AbdJLJbs (ORCPT ); Thu, 12 Oct 2017 05:31:48 -0400 Received: from mx07-00178001.pphosted.com ([62.209.51.94]:2850 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752665AbdJLJbp (ORCPT ); Thu, 12 Oct 2017 05:31:45 -0400 Subject: Re: [PATCH] i2c: stm32: Fixes multibyte transfer for STM32F4 I2C controller To: Radoslaw Pietrzyk , Wolfram Sang , Maxime Coquelin , Alexandre Torgue , "open list:I2C SUBSYSTEM" , "moderated list:ARM/STM32 ARCHITECTURE" , open list References: <1507722788-31224-1-git-send-email-radoslaw.pietrzyk@gmail.com> From: Pierre Yves MORDRET Message-ID: <990c3275-35b3-68da-453c-d1a80e867df7@st.com> Date: Thu, 12 Oct 2017 11:31:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <1507722788-31224-1-git-send-email-radoslaw.pietrzyk@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.49] X-ClientProxiedBy: SFHDAG8NODE3.st.com (10.75.127.24) To SFHDAG5NODE2.st.com (10.75.127.14) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-10-12_04:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/11/2017 01:53 PM, Radoslaw Pietrzyk wrote: > Do not read data on RXNE but on BTF only due to HW > synchronisation problems and NACKing read data too early. > It was found during testing of stmpe811 touchscreen driver. > Would you mind to explain what is behind "hw sync issue" you've seen ? > Signed-off-by: Radoslaw Pietrzyk > --- > drivers/i2c/busses/i2c-stm32f4.c | 11 +---------- > 1 file changed, 1 insertion(+), 10 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-stm32f4.c b/drivers/i2c/busses/i2c-stm32f4.c > index 4ec1084..86bcf4c 100644 > --- a/drivers/i2c/busses/i2c-stm32f4.c > +++ b/drivers/i2c/busses/i2c-stm32f4.c > @@ -409,16 +409,9 @@ static void stm32f4_i2c_handle_read(struct stm32f4_i2c_dev *i2c_dev) > * So, here we just disable buffer interrupt in order to avoid another > * system preemption due to RX not empty event. > */ > - case 2: > - case 3: > + default: > stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_ITBUFEN); > break; > - /* > - * For N byte reception with N > 3 we directly read data register > - * until N-2 data. > - */ > - default: > - stm32f4_i2c_read_msg(i2c_dev); > } > } > > @@ -470,8 +463,6 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev) > */ > reg = i2c_dev->base + STM32F4_I2C_CR1; > stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_ACK); > - stm32f4_i2c_read_msg(i2c_dev); > - break; > default: > stm32f4_i2c_read_msg(i2c_dev); > } >