> -----Original Message----- > From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> > Sent: 2019年4月11日 1:50 > To: Joakim Zhang <qiangqing.zhang@xxxxxxx>; wg@xxxxxxxxxxxxxx; > davem@xxxxxxxxxxxxx > Cc: dl-linux-imx <linux-imx@xxxxxxx>; linux-can@xxxxxxxxxxxxxxx; > netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [EXT] Re: [PATCH] can: dev: clean up CAN ctrlmode when close > CAN device > > On 4/10/19 9:55 AM, Joakim Zhang wrote: > > > >> -----Original Message----- > >> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> > >> Sent: 2019年4月10日 15:19 > >> To: Joakim Zhang <qiangqing.zhang@xxxxxxx>; wg@xxxxxxxxxxxxxx; > >> davem@xxxxxxxxxxxxx > >> Cc: dl-linux-imx <linux-imx@xxxxxxx>; linux-can@xxxxxxxxxxxxxxx; > >> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > >> Subject: [EXT] Re: [PATCH] can: dev: clean up CAN ctrlmode when close > >> CAN device > >> > >> On 4/10/19 8:27 AM, Joakim Zhang wrote: > >>> CAN driver always writes registers according to "ctrlmode", and now > >>> CAN framework will keep CAN ctrlmode after device closed. > >>> > >>> e.g. with following sequences: > >>> 1)ip link set can0 type can bitrate 1000000 loopback on 2)ip link > >>> set > >>> can0 up 3)ip link set can0 down 4)ip link set can0 type can bitrate > >>> 1000000 5)ip link set can0 up > >>> > >>> After this sequence, we may want to test loopback for the first time > >>> and not to test loopback second time. However, CAN device still keep > >>> "ctrlmode" as loopback on. > >> > >> Then you should configure loopback off in userspace. > > > > Got it. Thank you. > > > >>> This patch intends to clean up CAN ctrlmode when close CAN device. > >>> We can set which ctrlmode we need when open CAN device again. > >> > >> Consider a CANFD device, where CANFD has been enabled. It will feel > >> very weird if the interface looses the CANFD property by just a ifdown; ifup. > > > > Yes, you are right. But fd mode should compatible with normal can. > > CANFD was just an example. Take CAN_CTRLMODE_ONE_SHOT as another > example. You don't want your network device settings to vanish if you switch > the interface off and on again. > > > When I want to switch to normal can from fd mode. You mean that we > > should configure fd off in userspace as we may write some specific > > registers only by fd mode? > > Whatever mode you enable via user space use user space to disable them > again. Thank you for your detailed explanation. But in flexcan driver, it just set register bit when mode on and do not clear register bit when mode off, e.g. loopback, listennoly, 3 samples.... When we configure mode off after configured mode on in the user space, corresponding bit will not change. Is this should be improved in flexcan driver? Best Regards, Joakim Zhang > Marc > > -- > Pengutronix e.K. | Marc Kleine-Budde | > Industrial Linux Solutions | Phone: +49-231-2826-924 | > Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | > Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
