From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751650AbaCGIIz (ORCPT ); Fri, 7 Mar 2014 03:08:55 -0500 Received: from www.meduna.org ([92.240.244.38]:41334 "EHLO meduna.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750834AbaCGIIx (ORCPT ); Fri, 7 Mar 2014 03:08:53 -0500 Message-ID: <53197E8A.5050409@meduna.org> Date: Fri, 07 Mar 2014 09:08:42 +0100 From: Stanislav Meduna User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: wg@grandegger.com, mkl@pengutronix.de, linux-can@vger.kernel.org, "linux-kernel@vger.kernel.org" , "linux-rt-users@vger.kernel.org" Subject: FlexCAN on i.MX28 interrupt flooding retrying send X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Authenticated-User: stano@meduna.org X-Authenticator: dovecot_plain X-Spam-Score: -6.9 X-Spam-Score-Int: -68 X-Exim-Version: 4.72 (build at 25-Oct-2012 18:35:58) X-Date: 2014-03-07 09:08:48 X-Connected-IP: 95.105.163.217:3738 X-Message-Linecount: 90 X-Body-Linecount: 77 X-Message-Size: 3038 X-Body-Size: 2443 X-Received-Count: 1 X-Recipient-Count: 5 X-Local-Recipient-Count: 5 X-Local-Recipient-Defer-Count: 0 X-Local-Recipient-Fail-Count: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I am using a FlexCAN CAN controller on a Freescale i.MX28 platform [1]. If a packet is being sent when the bus is disconnected, I am getting an interrupt flooed that basically kills the machine. This is _not_ the same problem as [2] - my kernel already has the fix. The first interrupt comes with ESR 0x00028652, i.e. TXWRN_INT BIT1_ERR STF_ERR TX_WRN TXRX FLT_CONF error passive ERR_INT The next ones come the same without the acked TXWRN_INT. Reading the ESR again immediately after acking gives 0x00000250, i.e. TX_WRN TXRX FLT_CONF error passive so everything ackable has actually been acked. I think that the problem is that the FlexCAN tries to retransmit the frame indefinitely. Each retry senses the bus in the invalid state (BIT1_ERR) and immediately fires a new ERR_INT. To verify this I aborted the transmitted frame in the error state in the interrupt handler #define FLEXCAN_ESR_ERR_TRANSMIT \ (FLEXCAN_ESR_BIT1_ERR | FLEXCAN_ESR_BIT0_ERR | FLEXCAN_ESR_ACK_ERR) if (reg_esr & FLEXCAN_ESR_ERR_TRANSMIT) { /* In case of a transmission error the packet is retried and * if the error persists, we will get another interrupt right * away. Abort the transmission - a lost packet is better than * an irq storm. */ if(printk_ratelimit()) netdev_err(dev, "Aborted transmission, ESR %08x\n", reg_esr); can_get_echo_skb(dev, 0); flexcan_write(FLEXCAN_MB_CNT_CODE(0x4), ®s->cantxfg[FLEXCAN_TX_BUF_ID].can_ctrl); netif_wake_queue(dev); } and the problem disappeared as expected. However, the correct way is probably to retry during some reasonable (configurable?) time interval. What puzzles me is that I did not found any other instance of this problem in the relevant mailing lists, only the original [2]. I am using the 3.4.77 kernel with the realtime patches, but the code in the latest mainline looks the same in this respect. Maybe the realtime patches change some bevaviour, but I don't think they affect the core problem. I am not really an expert in the network devices, NAPI etc - maybe in that case the error interrupt should be disabled and re-enabled only if the error condition goes away? - I don't know... Please Cc: me when answering to the list. [1] http://www.tq-group.com/en/products/product-details/prod/embedded-modul-tqma28/extb/Main/productdetail/ [2] https://gitorious.org/linux-can/wg-linux-can-next/commit/8ad94fa Thanks -- Stano