On Mon, Jul 22, 2019 at 10:42:57AM +0300, Sergey Organov wrote:
> Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> writes:
>
> > On Fri, Jul 19, 2019 at 06:13:52PM +0300, Sergey Organov wrote:
> >> Hello Uwe,
> >>
> >> Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> writes:
> >> > Hello Sergey,
> >> >
> >> > On Fri, Jul 19, 2019 at 03:18:13PM +0300, Sergey Organov wrote:
> >> >> Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> writes:
> >> >> > On Fri, Jul 19, 2019 at 11:47:52AM +0300, Sergey Organov wrote:
> >> >> >> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> >> >> >> index 57d6e6b..95d7984 100644
> >> >> >> --- a/drivers/tty/serial/imx.c
> >> >> >> +++ b/drivers/tty/serial/imx.c
> >> >> >> @@ -405,7 +405,8 @@ static void imx_uart_rts_inactive(struct imx_port *sport, u32 *ucr2)
> >> >> >> /* called with port.lock taken and irqs caller dependent */
> >> >> >> static void imx_uart_rts_auto(struct imx_port *sport, u32 *ucr2)
> >> >> >> {
> >> >> >> - *ucr2 |= UCR2_CTSC;
> >> >> >> + if (*ucr2 & UCR2_CTS)
> >> >> >> + *ucr2 |= UCR2_CTSC;
> >> >> >
> >> >> > I think this patch is wrong or the commit log is insufficient.
> >> >> > imx_uart_rts_auto() has only a single caller and there ucr2 & UCR2_CTS is
> >> >> > never true. And CTSC isn't restored anywhere, is it?
> >> >>
> >> >> This is rebase to 'tty-next' branch, and you need to look at it in that
> >> >> context. There, ucr2 & UCR2_CTS does already make sense, due to previous
> >> >> fix that is already there.
> >> >
> >> > I looked at 57d6e6b which is the file you patched. And there
> >> > imx_uart_rts_auto is only ever called with *ucr2 not having UCR2_CTS.
> >> >
> >> > If you still think I'm wrong, please improve the commit log
> >> > accordingly.
> >>
> >> I still think you are wrong, but I don't know how to improve commit log.
> >>
> >> To check it once again, I just did:
> >>
> >> $ git show 57d6e6b > imx.c
> >>
> >> There, in imx_uart_set_termios(), I see:
> >>
> >> 1569: old_ucr2 = imx_uart_readl(sport, UCR2);
> >> 1570: ucr2 = old_ucr2 & (UCR2_TXEN | UCR2_RXEN | UCR2_ATEN | UCR2_CTS);
> >>
> >> Here, current UCR2 value is read into 'old_ucr2' and then its /current/
> >> UCR2_CTS bit is copied into 'ucr2' (along with 3 other bits).
> >>
> >> Then, later in the same function:
> >>
> >> 1591: imx_uart_rts_auto(sport, &ucr2);
> >>
> >> is called that can check /current/ state of UCR2_CTS bit in '*ucr2'.
> >>
> >> That's what the patch does, checks this bit.
> >>
> >> Sorry, I fail to see how you came to conclusion that "*ucr2 not having
> >> UCR2_CTS". Do we maybe still read different versions of the file?
> >
> > No, it's just that I failed to see that UCR2_CTS is in the set of bits
> > that are retained even when looking twice :-|
>
> Ah, that one... How familiar :-)
I thought again a bit over the weekend about this. I wonder if it's
correct to keep RTS active while going through .set_termios. Shouldn't
it maybe always be inactive to prevent the other side sending data while
we are changing the baud rate?
Best regards
Uwe
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