Hi Greg, > On Wed, Nov 24, 2021 at 10:56:43AM +0000, Sherry Sun wrote: > > Hi Greg, > > > > > -----Original Message----- > > > From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> > > > Sent: 2021年11月24日 17:59 > > > To: Sherry Sun <sherry.sun@xxxxxxx> > > > Cc: jirislaby@xxxxxxxxxx; u.kleine-koenig@xxxxxxxxxxxxxx; linux- > > > serial@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; dl-linux-imx > > > <linux- imx@xxxxxxx> > > > Subject: Re: [PATCH V2] tty: serial: imx: disable UCR4_OREN in > > > .stop_rx() instead of .shutdown() > > > > > > On Tue, Nov 23, 2021 at 06:51:22PM +0800, Sherry Sun wrote: > > > > From: Fugang Duan <fugang.duan@xxxxxxx> > > > > > > > > Disable the UCR4_OREN bit in .stop_rx() before the uart receiver > > > > is disabled maybe better than in the .shutdown() function. > > > > > > Why is it better? What does this "fix"? > > > > Since I am not clear about the history of this patch, so I haven't found any > obvious issues without this patch so far. > > Then why submit it? Because from the code logic, I think this patch is more reasonable. > > > But after discussing with the IP owner, it is still recommended to disable the > receiver-related interrupts like OREN before disabling the receiver. > > recommended by what? The hardware designers? Yes, the i.MX UART IP designer. > > > If not, when we have the overrun error during the receiver disable process, > the overrun interrupt will keep trigging until we disable the OREN interrupt in > the .shutdown(), because the ORE status can only be cleared when read the > rx FIFO or reset the controller. Although the called time between the receiver > disable and OREN disable in .shutdown() is very short, there is still the risk of > endless interrupt during this short period of time. So had better to disable > OREN before the receiver been disabled in .stop_rx(). > > Please document this in the changelog, otherwise we have no idea why this is > needed. Sure, I will send V3 and add these info into the commit message. Thanks! Best regards Sherry
