From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andri Yngvason Subject: Re: [PATCH v5 2/5] can: kvaser_usb: Consolidate and unify state change handling Date: Mon, 26 Jan 2015 10:21:34 +0000 Message-ID: <20150126102134.16360.18418@shannon> References: <20150120214409.GA16828@linux> <20150121103319.14511.57709@shannon> <20150121144323.GA17070@linux> <20150121150015.31351.6605@shannon> <20150121153647.GB17070@linux> <49707d45a389a1acb9ccec4295d05762@grandegger.com> <20150123060734.GA7949@Darwish.PC> <20150123103213.6205.54618@shannon> <20150125024300.GA6028@Darwish.PC> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Return-path: Received: from mail-am1on0059.outbound.protection.outlook.com ([157.56.112.59]:58400 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755122AbbAZKVn convert rfc822-to-8bit (ORCPT ); Mon, 26 Jan 2015 05:21:43 -0500 In-Reply-To: <20150125024300.GA6028@Darwish.PC> Sender: linux-can-owner@vger.kernel.org List-ID: To: "Ahmed S. Darwish" Cc: Wolfgang Grandegger , Olivier Sobrie , Oliver Hartkopp , Marc Kleine-Budde , Linux-CAN , netdev , LKML Quoting Ahmed S. Darwish (2015-01-25 02:43:00) > On Fri, Jan 23, 2015 at 10:32:13AM +0000, Andri Yngvason wrote: > > Quoting Ahmed S. Darwish (2015-01-23 06:07:34) > > > On Wed, Jan 21, 2015 at 05:13:45PM +0100, Wolfgang Grandegger wrote: > > > > On Wed, 21 Jan 2015 10:36:47 -0500, "Ahmed S. Darwish" > > > > wrote: > > > > > On Wed, Jan 21, 2015 at 03:00:15PM +0000, Andri Yngvason wrote: > > > > >> Quoting Ahmed S. Darwish (2015-01-21 14:43:23) > > > > >> > Hi! > > > > > > > > > > ... > > > > > > > > > >> > <-- Unplug the cable --> > > > > >> > > > > > >> > (000.009106) can0 20000080 [8] 00 00 00 00 00 00 08 00 > > > > >> > ERRORFRAME > > > > >> > bus-error > > > > >> > error-counter-tx-rx{{8}{0}} > > > > >> > (000.001872) can0 20000080 [8] 00 00 00 00 00 00 10 00 > > > > > > > > For a bus-errors I would also expcect some more information in the > > > > data[2..3] fields. But these are always zero. > > > > > > > > > > M16C error factors made it possible to report things like > > > CAN_ERR_PROT_FORM/STUFF/BIT0/BIT1/TX in data[2], and > > > CAN_ERR_PROT_LOC_ACK/CRC_DEL in data[3]. > > > > > > Unfortunately such error factors are only reported in Leaf, but > > > not in USBCan-II due to the wire format change in the error event: > > > > > > struct leaf_msg_error_event { > > > u8 tid; > > > u8 flags; > > > __le16 time[3]; > > > u8 channel; > > > u8 padding; > > > u8 tx_errors_count; > > > u8 rx_errors_count; > > > u8 status; > > > u8 error_factor; > > > } __packed; > > > > > > struct usbcan_msg_error_event { > > > u8 tid; > > > u8 padding; > > > u8 tx_errors_count_ch0; > > > u8 rx_errors_count_ch0; > > > u8 tx_errors_count_ch1; > > > u8 rx_errors_count_ch1; > > > u8 status_ch0; > > > u8 status_ch1; > > > __le16 time; > > > } __packed; > > > > > > I speculate that the wire format was changed due to controller > > > bugs in the USBCan-II, which was slightly mentioned in their > > > data sheets here: > > > > > > http://www.kvaser.com/canlib-webhelp/page_hardware_specific_can_controllers.html > > > > > > So it seems there's really no way for filling such bus error > > > info given the very limited amount of data exported :-( > > > > > We experienced similar problems with FlexCAN. > > Hmm, I'll have a look there then... > > Although my initial instincts imply that the FlexCAN driver has > access to the raw CAN registers, something I'm unable to do here. > But maybe there's some black magic I'm missing :-) > Yes, it's memory mapped. > > [...] > > > > > > > I've dumped _every_ message I receive from the firmware while > > > disconnecting the CAN bus, waiting a while, and connecting it again. > > > I really received _nothing_ from the firmware when the CAN bus was > > > reconnected and the data packets were flowing again. Not even a > > > single CHIP_STATE_EVENT, even after waiting for a long time. > > > > > > So it's basically: > > > ... > > > ERR EVENT, txerr=128, rxerr=0 > > > ERR EVENT, txerr=128, rxerr=0 > > > ERR EVENT, txerr=128, rxerr=0 > > > ... > > > > > > then complete silence, except the data frames. I've even tried with > > > different versions of the firmware, but the same behaviour persisted. > > > > > > > > So, What can the driver do given the above? > > > > > > > > Little if the notification does not come. > > > > > > > > > > We can poll the state by sending CMD_GET_CHIP_STATE to the firmware, > > > and it will hopefully reply with a CHIP_STATE_EVENT response > > > containing the new txerr and rxerr values that we can use for > > > reverse state transitions. > > > > > > But do we _really_ want to go through the path? I feel that it will > > > open some cans of worms w.r.t. concurrent access to both the netdev > > > and USB stacks from a single driver. > > > > > Honestly, I don't know. > > > > > > A possible solution can be setting up a kernel thread that queries > > > for a CHIP_STATE_EVENT every second? > > > > > Have you considered polling in kvaser_usb_tx_acknowledge? You could do something > > like: > > if(unlikely(dev->can.state != CAN_STATE_ERROR_ACTIVE)) > > { > > request_state(); > > } > > > > OK, I have four important updates on this issue: > > a) My initial testing was done on high-speed channel, at a bitrate > of 50K. After setting the bus to a more reasonable bitrate 500K > or 1M, I was _consistently_ able to receive CHIP_STATE_EVENTs > when plugging the CAN connector again after an unplug. > > b) The error counters on this device do not get reset on plugging > after an unplug. I've setup a kernel thread [2] that queries > the chip state event every second, and the error counters stays > the same all the time. [1] > > c) There's a single case when the erro counters do indeed get > reversed, and it happens only when introducing some noise in > the bus after the re-plug. In that case, the new error events > get raised with new error counters starting from 0/1 again. > > d) I've discovered a bug that forbids the CAN state from > returning to ERROR_ACTIVE in case of the error counters > numbers getting decreased. But independent from that bug, the > verbose debugging messages clearly imply that we only get the > error counters decreased in the case mentioned at `c)' above. > > So from [1] and [2], it's now clear that the device do not reset > these counters back in the re-plug case. I'll give a check to > flexcan as advised, but unfortunately I don't really think there's > much I can do about this. > > [1] > > [ 877.207082] CAN_ERROR_: channel=0, txerr=88, rxerr=0 > [ 877.207090] CAN_ERROR_: channel=0, txerr=136, rxerr=0 > [ 877.207094] CAN_ERROR_: channel=0, txerr=144, rxerr=0 > [ 877.207098] CAN_ERROR_: channel=0, txerr=152, rxerr=0 > [ 877.207100] CAN_ERROR_: channel=0, txerr=160, rxerr=0 > [ 877.207102] CAN_ERROR_: channel=0, txerr=168, rxerr=0 > [ 877.208075] CAN_ERROR_: channel=0, txerr=200, rxerr=0 > > (( The above error event, staying the same at txerr=200 keeps > flooding the bus until the CAN cable is re-plugged )) > > [ 878.225116] CHIP_STATE: channel=0, txerr=200, rxerr=0 > [ 878.225143] CHIP_STATE: channel=1, txerr=0, rxerr=0 > [ 879.265167] CHIP_STATE: channel=0, txerr=200, rxerr=0 > [ 879.267152] CHIP_STATE: channel=1, txerr=0, rxerr=0 > [ 879.265167] CHIP_STATE: channel=0, txerr=200, rxerr=0 > [ 879.267152] CHIP_STATE: channel=1, txerr=0, rxerr=0 > > (( The same counters get repeated every second )) > > [2] State was polled using: > > static int kvaser_usb_poll_chip_state(void *vpriv) { > struct kvaser_usb_net_priv *priv = vpriv; > > while (!kthread_should_stop()) { > kvaser_usb_simple_msg_async(priv, CMD_GET_CHIP_STATE); > ssleep(1); > } > > return 0; > } > > > I don't think that anything beyond that would be worth pursuing. > > > > I agree, but given the new input, it seems that our problem > extends to the error counters themselves not getting decreased > on re-plug. So, even polling will not solve the issue: we'll > get the same txerr/rxerr values again and again :-( > Well, that's a damn shame. Not much you can do about that. Best regards, Andri