From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751639AbcJBOUT (ORCPT ); Sun, 2 Oct 2016 10:20:19 -0400 Received: from smtp.domeneshop.no ([194.63.252.55]:47932 "EHLO smtp.domeneshop.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750820AbcJBOUJ (ORCPT ); Sun, 2 Oct 2016 10:20:09 -0400 Subject: Re: [PATCH v3 2/7] i2c: bcm2835: Protect against unexpected TXW/RXR interrupts To: Stefan Wahren , Eric Anholt , wsa@the-dreams.de, swarren@wwwdotorg.org References: <1475085056-5205-1-git-send-email-noralf@tronnes.org> <1475085056-5205-3-git-send-email-noralf@tronnes.org> <87oa37fzx6.fsf@eliezer.anholt.net> <1708178720.178936.b155d019-5320-4754-bbe2-4afc1ae71cd6.open-xchange@email.1und1.de> Cc: linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org From: =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= Message-ID: <0c943ee9-d152-79c4-2ad7-8a88c2d9c960@tronnes.org> Date: Sun, 2 Oct 2016 16:19:57 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <1708178720.178936.b155d019-5320-4754-bbe2-4afc1ae71cd6.open-xchange@email.1und1.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Den 29.09.2016 07:37, skrev Stefan Wahren: >> Noralf Trønnes hat am 29. September 2016 um 00:22 >> geschrieben: >> >> >> >> Den 29.09.2016 00:00, skrev Eric Anholt: >>> Noralf Trønnes writes: >>> >>>> If an unexpected TXW or RXR interrupt occurs (msg_buf_remaining == 0), >>>> the driver has no way to fill/drain the FIFO to stop the interrupts. >>>> In this case the controller has to be disabled and the transfer >>>> completed to avoid hang. >>>> >>>> (CLKT | ERR) and DONE interrupts are completed in their own paths, and >>>> the controller is disabled in the transfer function after completion. >>>> Unite the code paths and do disabling inside the interrupt routine. >>>> >>>> Clear interrupt status bits in the united completion path instead of >>>> trying to do it on every interrupt which isn't necessary. >>>> Only CLKT, ERR and DONE can be cleared that way. >>>> >>>> Add the status value to the error value in case of TXW/RXR errors to >>>> distinguish them from the other S_LEN error. >>> I was surprised that not writing the TXW/RXR bits on handling their >>> interrupts was OK, given that we were doing so before, but it's a level >>> interrupt and those bits are basically ignored on write. >>> >>> This patch and 3, 4, and 6 are: >>> >>> Reviewed-by: Eric Anholt >>> >>> Patch 5 is: >>> >>> Acked-by: Eric Anholt >>> >>> Note for future debug: The I2C_C_CLEAR on errors will take some time to >>> resolve -- if you were in non-idle state and I2C_C_READ, it sets an >>> abort_rx flag and runs through the state machine to send a NACK and a >>> STOP, I think. Since we're setting CLEAR without I2CEN, that NACK will >>> be hanging around queued up for next time we start the engine. >> Maybe you're able to explain the issues I had with reset: >> https://github.com/raspberrypi/linux/issues/1653 >> >> Should we put your note into the commit message? >> It will most likely be lost if it just stays in this email. > I prefer to have this kind of information as a code comment. Eric, does this look good to you as a code comment: /* * Note about I2C_C_CLEAR on error: * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through * the state machine to send a NACK and a STOP. Since we're setting CLEAR * without I2CEN, that NACK will be hanging around queued up for next time * we start the engine. */ If it is, I'll resend the series with this change and add all the ack's and r-b's. Noralf.