> -----Original Message----- > From: Michael Walle <michael@xxxxxxxx> > Sent: 2022年11月23日 19:09 > To: Sherry Sun <sherry.sun@xxxxxxx> > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; jirislaby@xxxxxxxxxx; > jingchang.lu@xxxxxxxxxxxxx; tomonori.sakita@xxxxxxxxxx; > atsushi.nemoto@xxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx> > Subject: Re: [PATCH V2 2/5] tty: serial: fsl_lpuart: clear UARTCTRL_LOOPS in > lpuart32_shutdown() > > Am 2022-11-23 11:58, schrieb Sherry Sun: > >> -----Original Message----- > >> From: Michael Walle <michael@xxxxxxxx> > >> Sent: 2022年11月23日 18:34 > >> To: Sherry Sun <sherry.sun@xxxxxxx> > >> Cc: gregkh@xxxxxxxxxxxxxxxxxxx; jirislaby@xxxxxxxxxx; > >> jingchang.lu@xxxxxxxxxxxxx; tomonori.sakita@xxxxxxxxxx; > >> atsushi.nemoto@xxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx; linux- > >> kernel@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx> > >> Subject: Re: [PATCH V2 2/5] tty: serial: fsl_lpuart: clear > >> UARTCTRL_LOOPS in > >> lpuart32_shutdown() > >> > >> Am 2022-11-10 09:17, schrieb Sherry Sun: > >> > UARTCTRL_LOOPS bit is set in lpuart32_set_mctrl() for loopback > >> > mode, but nowhere clear this bit, it should be cleared when closing > >> > the uart port to avoid the loopback mode been enabled by default > >> > when reopening the uart. > >> > >> It's cleared in set_mctrl(). What is the expectation from the serial > >> core here? > >> > > > > Hi Michael, > > > > If we call .set_mctrl(TIOCM_LOOP), the UARTCTRL_LOOPS will be set. > > Then when we call .shutdown(), serial core won't call .set_mctrl() to > > clear it, so the UARTCTRL_LOOPS need to be cleared here. > > Per my understanding, .shutdown() should clean up all the uart flags, > > as the transmitter and receiver will been disabled, we will > > re-configure all the settings needed when re-open the port. > > Two things, > (1) should the loopback be cleared on a newly opened serial device? > (2) as mentioned in my other reply, this can also be handled in > the startup. Eg. the startup can clear the loopback flag. > (together with possible hardware events). > > I'm not that deep into the serial core, thus my question about the > expectations from the serial core. I guess the answer to > (1) is yes, but better to ask. > Hi Michael, For the (1), I have checked the serial core, seems the answer is no, . startup() won't clean the status, only when the uart device is probed, lpuart will do the global reset to all the registers instead of .startup(). So I think the uart running status cleared in .shutdown() is reasonable. Best Regards Sherry
