From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Subject: Re: CAN messages being lost on i.MX25 with flexcan Date: Thu, 19 Apr 2012 15:37:04 +0200 Message-ID: <4F901500.9070009@grandegger.com> References: <4F8FEF02.7040503@grandegger.com> <4F8FFAB3.1040906@grandegger.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from ngcobalt02.manitu.net ([217.11.48.102]:40093 "EHLO ngcobalt02.manitu.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753313Ab2DSNhI (ORCPT ); Thu, 19 Apr 2012 09:37:08 -0400 In-Reply-To: Sender: linux-can-owner@vger.kernel.org List-ID: To: Martin Kozusky Cc: linux-can@vger.kernel.org On 04/19/2012 01:58 PM, Martin Kozusky wrote: > Dne 19.4.2012 13:44, Wolfgang Grandegger napsal(a): >> On 04/19/2012 01:21 PM, Martin Kozusky wrote: >>> Dne 19.4.2012 12:54, Wolfgang Grandegger napsal(a): >>>> On 04/19/2012 12:04 PM, Martin Kozusky wrote: >>>>> Hello, >>>>> I'm using Voipac i.MX25 module with flexcan, kernel 2.6.38.9. >>>>> I'm sending the data at 250kbps, around 1100 msgs/sec. When I >>>>> enable the >>>>> canbus interface (canconfig can0 start), CPU load is higher, that is >>>>> understandable, there are many interrupts. I'm not doing anything else >>>>> then using recvmsg (or recvmmsg which is little better), but some >>>>> messages are still lost (around 1500 messages lost from 467 000 being >>>>> send from another source). When I start doing something (like "cat >>>>> /proc/interrupts", or write to file), many more messages are lost. >>>>> >>>>> Do you have any idea how to fix this? I need to make some CAN messages >>>>> logger and I cannot lose any message (idealy :) So I made big >>>>> buffer in >>>>> my program so that I don't need to write the messages into the file >>>>> while "recording" is enabled, after "recording" is switched off, I >>>>> write >>>>> the buffer into the file, but that is still not good enough. >>>>> Is there any way how to write to some buffer directly in flexcan >>>>> driver >>>>> (the best would be in the IRQ routine) and then read messages from >>>>> this >>>>> buffer in my program? >>>>> Or are just interrupts lost when doing something else in the system >>>>> and >>>>> I cannot fix this? Or can I somehow specify that "can rx >>>>> interrupts" has >>>>> highest prioroty? >>>> >>>> Do you already know where the packets are dropped (get lost). Maybe >>>> your >>>> user space app is simply not faster enough to process them in time. You >>>> can check that with the candump option "-d". >>> >>> Hello Wolfgang, >>> I don't know where it gets lost. But I'm just making select() and >>> recvmmsg in my app now. >>> Now when I'm trying candump -d, it shows messages and between that: >>> >>> can0 18FFC33D [8] 4A E6 00 00 03 00 00 F6 >>> can0 1CEFB8F3 [8] 34 42 23 3D 8C 01 00 00 >>> DROPCOUNT: dropped 245 CAN frames on 'can0' socket (total drops 30886) >>> can0 18FF0AEF [8] 70 76 46 7C A7 9E 2A 6A >>> can0 18FF0AF0 [8] B0 7E FB 7D A7 DC 27 69 >>> can0 18FEBF0B [8] F5 03 79 81 69 74 6E 79 >>> >>> I've sent around 40 000 messages. >>> Does this help somehow to identify where the problem is? >> >> Yes, you are loosing messages because your app is not faster enough. >> >>> I found out that if I (in my program) don't printf every frame, then >>> dropcount is better, so I think when candump would only show dropps and >>> not every frame then it would also get better. >> >> printf takes time, of course. Therefore everything which makes your app >> reading the messages faster will help including increasing the >> scheduling priority of the process/thread. Also increasing the size of >> the receive buffer may help. Try candump with the "-r" option. > > I tried -r 10000000 > > and the result was that dropping started some time later then it would > normaly. From 467 000 packets, total drops was 103064. That is better > ratio than before. But few times, my system was stucked for a while, > then it recovered and continued to work. So I will try to use this > buffer size in my program, without printf and I will see how many > packets I lose. If other activities delay your app too much, your are in trouble. Proper thread priorities may help. > Is there a way how to get actual used size of the buffer? getsockopt? >>> This is my /proc/interrupts >>> >>> root@vmx25 /opt$ cat /proc/interrupts >>> CPU0 >>> 0: 0 - spi_imx >>> 5: 32827 - IMX-uart >>> 9: 129 - sdhci >>> 13: 0 - spi_imx >>> 25: 5 - imxdi_rtc >>> 33: 12168 - mxc_nand >>> 34: 1 - mxc-sdma >>> 37: 109275 - ehci_hcd:usb1 >>> 43: 1624971 - can0 >>> 46: 0 - mxcadc >>> 54: 195357 - i.MX Timer Tick >>> 164: 0 - ESDHCI card 0 detect >>> Err: 0 >> >> In a first place, I don't think your are loosing messages because they >> are not read-out faster enough from the CAN controller. >> >>> I have another problem - when I send messages and nobody is acking them >>> (no other device on CANbus), system stops responding until I put another >>> device onto CANbus, but I think I should start new thread with this. >> >> What kernel version do you use? Do you use the flexcan driver from that >> kernel? The problem is bus errors coming at high rate. > > I'm using 2.6.35.9 Preempt, the flexcan.c driver is original. IIRC, that kernel version did not include the flexcan driver. It entered with 2.6.36. Anyway, maybe the following patch helps: http://patchwork.ozlabs.org/patch/130761/ Wolfgang.