linux-kernel - RE: [PATCH] tty: serial: imx: clear RTSD status before suspend

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Date:   Tue, 23 Nov 2021 10:20:50 +0000
From:   Sherry Sun <sherry.sun@....com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "jirislaby@...nel.org" <jirislaby@...nel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH] tty: serial: imx: clear RTSD status before suspend

Hi Uwe,

> 
> On Tue, Nov 23, 2021 at 08:41:18AM +0000, Sherry Sun wrote:
> > Hi Uwe,
> >
> > > -----Original Message-----
> > > From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > > Sent: 2021年11月23日 15:42
> > > To: Sherry Sun <sherry.sun@....com>
> > > Cc: gregkh@...uxfoundation.org; jirislaby@...nel.org; linux-
> > > serial@...r.kernel.org; linux-kernel@...r.kernel.org; dl-linux-imx
> > > <linux- imx@....com>
> > > Subject: Re: [PATCH] tty: serial: imx: clear RTSD status before
> > > suspend
> > >
> > > On Tue, Nov 23, 2021 at 03:03:49PM +0800, Sherry Sun wrote:
> > > > From: Fugang Duan <fugang.duan@....com>
> > > >
> > > > Clear RTSD status before suspend due to the port also use RTS pin
> > > > as wakeup source, need to clear the flag first.
> > >
> > > I'd write:
> > >
> > > 	Clear RTSD status before enabling the irq event for RTSD.
> >
> > Thanks for the suggestion, I will reorganize the commit message and send
> V2.
> >
> > >
> > > That this happens in the context of suspend isn't that important.
> >
> > Sorry I didn't get the point here, can you please explain more?
> > Per my understanding, the wakeup source interrupt is handled in the
> > suspend context, so clear the flag in the suspend context is also
> > necessary.
> 
> But the actual problem is that RTSD is enabled without first clearing it and
> not that RTSD isn't cleared in suspend.
> 
> So my initial reaction after reading the commit log header "clear RTSD status
> before suspend" was: WTH, why do we need clearing RTSD before suspend.
> Shouldn't the RTSD state kept over suspend?
> 
> In contrast clearing an event before the respecive irq is enabled is more
> obviously correct. And if the irq source is enabled as part of suspend or open
> isn't that relevant for the subject line.
> 

Got your point now, thanks for the explanation.
The patch subject is indeed ambiguous, I will fix it in V2.

Best regards
Sherry