Re: imx-serial: RX DMA startup latency

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Jul 13, 2017 at 11:00:00AM -0300, Fabio Estevam wrote:
> Hi Greg,
> 
> On Thu, Jul 13, 2017 at 9:24 AM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Wed, Jul 12, 2017 at 07:05:06PM -0300, Fabio Estevam wrote:
> >> From: Peter Senna Tschudin <peter.senna@collabora.com>
> >>
> >> commit 4dec2f119e86f9c91e60cdd8f0cc057452e331a9 upstream.
> >>
> >> 18a4208 introduced a change to reduce the RX DMA latency on the first reception
> >> when the serial port was opened for reading. However it was claiming a hardirq
> >> unsafe lock after a hardirq safe lock which is not allowed and causes lockdep
> >> to complain verbosely.
> >>
> >> This patch changes the code to always start RX DMA earlier, instead of
> >> relying on the flags used to open the serial port removing the code that
> >> was looking for the serial file flags.
> >>
> >> Cc: <stable@vger.kernel.org> #4.12.x
> >> Signed-off-by: Peter Senna Tschudin <peter.senna@collabora.com>
> >> Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
> >> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >> Signed-off-by: Fabio Estevam <festevam@gmail.com>
> >> ---
> >>  drivers/tty/serial/imx.c | 26 +++++---------------------
> >>  1 file changed, 5 insertions(+), 21 deletions(-)
> >
> > What are you asking for here, for this to be added to the 4.12-stable
> > tree?
> 
> Yes, correct.
> 
> I thought that adding "Cc: <stable@vger.kernel.org> #4.12.x" would
> make it clear.

That makes it look like any other patch being submitted upstream.

> What should I have made differently?

Below the --- line, say "Can you apply this patch to...", or even
simpler yet, just a short email saying, "Can you apply commit XXXXXX to
the 4.12-stable tree?"

anyway, will go queue this up now, thanks.

greg k-h