[v2,1/1] serial: 8250_dw: Allow hardware flow control to be used

Commit Message

James Hogan March 3, 2017, 11:23 p.m. UTC

On Fri, Mar 03, 2017 at 03:31:06PM +0200, Andy Shevchenko wrote:
> On Fri, 2017-03-03 at 00:21 +0000, James Hogan wrote:
> > The CONFIG_HAVE_CLK=n implementation of devm_clk_get() in particular
> > seems highly questionable to me, given that commit 93abe8e4b13a ("clk:
> > add non CONFIG_HAVE_CLK routines") which added it 5 years ago says:
> > 
> > > These calls will return error for platforms that don't select
> > > HAVE_CLK
> > 
> > And NULL isn't an error in this API.
> 
> Which is okay. I dunno what should be returned from clk_round_rate() if
> clk is NULL. I would fix CLK framework, though I would like to gather
> more details.

Hmm, the common clock framwork is just one implementation of the clock
API that won't use NULL as a valid clock handle. HAVE_CLK=n is just
another implementation that does return NULL as a valid value, and
accepts that value in the other clk functions.

> Btw, I hope you also noticed this one:
> 
> http://www.spinics.net/lists/linux-serial/msg25314.html

Interesting.

Following Russel's past advise[1], the following patch on top of Heiko's
patch also fixes things for me on Octeon:

[1] https://lists.gt.net/linux/kernel/2102623

If thats an acceptable fix I'll post it properly. Thoughts?

Cheers
James

Comments

Andy Shevchenko March 4, 2017, 2:56 a.m. UTC | #1

On Sat, Mar 4, 2017 at 1:23 AM, James Hogan <[e-mail]> wrote:
> On Fri, Mar 03, 2017 at 03:31:06PM +0200, Andy Shevchenko wrote:
>> On Fri, 2017-03-03 at 00:21 +0000, James Hogan wrote:
>> > The CONFIG_HAVE_CLK=n implementation of devm_clk_get() in particular
>> > seems highly questionable to me, given that commit 93abe8e4b13a ("clk:
>> > add non CONFIG_HAVE_CLK routines") which added it 5 years ago says:

>> Btw, I hope you also noticed this one:
>>
>> http://www.spinics.net/lists/linux-serial/msg25314.html
>
> Interesting.
>
> Following Russel's past advise[1], the following patch on top of Heiko's
> patch also fixes things for me on Octeon:
>
> [1] https://lists.gt.net/linux/kernel/2102623
>
> If thats an acceptable fix I'll post it properly. Thoughts?

Fine by me. Looks definitely better than IS_ERR_OR_NULL().

Please, submit as usual with your SoB tag.

> diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> index 223ac234ddb2..e65808c482f1 100644
> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -267,6 +267,8 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
>         rate = clk_round_rate(d->clk, baud * 16);
>         if (rate < 0)
>                 ret = rate;
> +       else if (rate == 0)
> +               ret = -ENOENT;
>         else
>                 ret = clk_set_rate(d->clk, rate);
>         clk_prepare_enable(d->clk);

Patch

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 223ac234ddb2..e65808c482f1 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -267,6 +267,8 @@  static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 	rate = clk_round_rate(d->clk, baud * 16);
 	if (rate < 0)
 		ret = rate;
+	else if (rate == 0)
+		ret = -ENOENT;
 	else
 		ret = clk_set_rate(d->clk, rate);
 	clk_prepare_enable(d->clk);