Messages in this thread | | | Date | Thu, 30 Mar 2023 14:46:16 +0800 | Subject | Re: [PATCH V3] can: usb: f81604: add Fintek F81604 support | From | Peter Hong <> |
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Hi Vincent,
Vincent MAILHOL 於 2023/3/28 下午 12:49 寫道: >>>> +static int f81604_set_reset_mode(struct net_device *netdev) >>>> +{ >>>> + struct f81604_port_priv *priv = netdev_priv(netdev); >>>> + int status, i; >>>> + u8 tmp; >>>> + >>>> + /* disable interrupts */ >>>> + status = f81604_set_sja1000_register(priv->dev, netdev->dev_id, >>>> + SJA1000_IER, IRQ_OFF); >>>> + if (status) >>>> + return status; >>>> + >>>> + for (i = 0; i < F81604_SET_DEVICE_RETRY; i++) { >>> Thanks for removing F81604_USB_MAX_RETRY. >>> >>> Yet, I still would like to understand why you need one hundred tries? >>> Is this some paranoiac safenet? Or does the device really need so many >>> attempts to operate reliably? If those are needed, I would like to >>> understand the root cause. >> This section is copy from sja1000.c. In my test, the operation/reset may >> retry 1 times. >> I'll reduce it from 100 to 10 times. > Is it because the device is not ready? Does this only appear at > startup or at random?
I'm using ip link up/down to test open/close(). It's may not ready so fast. but the maximum retry is only 1 for test 10000 times.
>>>> +static int f81604_set_termination(struct net_device *netdev, u16 term) >>>> +{ >>>> + struct f81604_port_priv *port_priv = netdev_priv(netdev); >>>> + struct f81604_priv *priv; >>>> + u8 mask, data = 0; >>>> + int r; >>>> + >>>> + priv = usb_get_intfdata(port_priv->intf); >>>> + >>>> + if (netdev->dev_id == 0) >>>> + mask = F81604_CAN0_TERM; >>>> + else >>>> + mask = F81604_CAN1_TERM; >>>> + >>>> + if (term == F81604_TERMINATION_ENABLED) >>>> + data = mask; >>>> + >>>> + mutex_lock(&priv->mutex); >>> Did you witness a race condition? >>> >>> As far as I know, this call back is only called while the network >>> stack big kernel lock (a.k.a. rtnl_lock) is being hold. >>> If you have doubt, try adding a: >>> >>> ASSERT_RTNL() >>> >>> If this assert works, then another mutex is not needed. >> It had added ASSERT_RTNL() into f81604_set_termination(). It only assert >> in f81604_probe() -> f81604_set_termination(), not called via ip command: >> ip link set dev can0 type can termination 120 >> ip link set dev can0 type can termination 0 >> >> so I'll still use mutex on here. > Sorry, do you mean that the assert throws warnings for f81604_probe() > -> f81604_set_termination() but that it is OK (no warning) for ip > command? > > I did not see that you called f81604_set_termination() internally. > Indeed, rtnl_lock is not held in probe(). But I think it is still OK. > In f81604_probe() you call f81604_set_termination() before > register_candev(). If the device is not yet registered, > f81604_set_termination() can not yet be called via ip command. Can you > describe more precisely where you think there is a concurrency issue? > I still do not see it.
Sorry, I had inverse the mean of ASSERT_RTNL(). It like you said. f81604_probe() not held rtnl_lock. ip set terminator will held rtnl_lock.
Due to f81604_set_termination() will called by f81604_probe() to initialize, it may need mutex in situation as following:
User is setting can0 terminator when f81604_probe() complete generate can0 and generating can1. So IMO, the mutex may needed.
>>>> + port_priv->can.do_get_berr_counter = f81604_get_berr_counter; >>>> + port_priv->can.ctrlmode_supported = >>>> + CAN_CTRLMODE_LISTENONLY | CAN_CTRLMODE_3_SAMPLES | >>>> + CAN_CTRLMODE_ONE_SHOT | CAN_CTRLMODE_BERR_REPORTING | >>>> + CAN_CTRLMODE_CC_LEN8_DLC | CAN_CTRLMODE_PRESUME_ACK; >>> Did you test the CAN_CTRLMODE_CC_LEN8_DLC feature? Did you confirm >>> that you can send and receive DLC greater than 8? >> Sorry, I had misunderstand the define. This device is only support 0~8 >> data length, > ^^^^^^^^^^^ > > Data length or Data Length Code (DLC)? Classical CAN maximum data > length is 8 but maximum DLC is 15 (and DLC 8 to 15 mean a data length > of 8). >
This device can't support DLC > 8. It's only support 0~8.
Thanks
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