linux-kernel - Re: [PATCH v2] serial: 8250_dw: Improve unwritable LCR workaround

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Date:	Tue, 10 Dec 2013 22:48:06 +0000
From:	James Hogan <james.hogan@...tec.com>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Tim Kryger <tim.kryger@...aro.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	linux-serial@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Patch Tracking <patches@...aro.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Lior Amsalem <alior@...vell.com>,
	Jason Cooper <jason@...edaemon.net>,
	ARM Kernel List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] serial: 8250_dw: Improve unwritable LCR workaround

On Tuesday 10 December 2013 09:11:55 Ezequiel Garcia wrote:
> Hi Tim, James:
> 
> On Mon, Dec 09, 2013 at 04:42:23PM -0800, Tim Kryger wrote:
> > On Fri, Dec 6, 2013 at 4:59 PM, James Hogan <james.hogan@...tec.com> 
wrote:
> [..]
> 
> > diff --git a/drivers/tty/serial/8250/8250_dw.c
> > b/drivers/tty/serial/8250/8250_dw.c
> > index 4658e3e..5f096c7 100644
> > --- a/drivers/tty/serial/8250/8250_dw.c
> > +++ b/drivers/tty/serial/8250/8250_dw.c
> > @@ -96,7 +96,8 @@ static void dw8250_serial_out(struct uart_port *p,
> > int offset, int value)
> > 
> >         if (offset == UART_LCR) {
> >         
> >                 int tries = 1000;
> >                 while (tries--) {
> > 
> > -                       if (value == p->serial_in(p, UART_LCR))
> > +                       unsigned int lcr = p->serial_in(p, UART_LCR);
> > +                       if ((value & ~UART_LCR_SPAR) == (lcr &
> > ~UART_LCR_SPAR))> 
> >                                 return;
> >                         
> >                         dw8250_force_idle(p);
> >                         writeb(value, p->membase + (UART_LCR <<
> >                         p->regshift));
> > 
> > @@ -132,7 +133,8 @@ static void dw8250_serial_out32(struct uart_port
> > *p, int offset, int value)
> > 
> >         if (offset == UART_LCR) {
> >         
> >                 int tries = 1000;
> >                 while (tries--) {
> > 
> > -                       if (value == p->serial_in(p, UART_LCR))
> > +                       unsigned int lcr = p->serial_in(p, UART_LCR);
> > +                       if ((value & ~UART_LCR_SPAR) == (lcr &
> > ~UART_LCR_SPAR))> 
> >                                 return;
> >                         
> >                         dw8250_force_idle(p);
> >                         writel(value, p->membase + (UART_LCR <<
> >                         p->regshift));
> > 
> > Would you mind posting this for proper review so we can get the fix in?
> 
> Applying this change fixes all the problems I reported (just did a quick
> test on the board I have currently on my desk).
> 
> Nice work!

Thanks for testing it.

I've posted Tim's version for proper review with both your tested-by.

Cheers
James
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