Re: [PATCHv2 2/5] driver: serial: omap: prevent runtime PM for "no_console_suspend"

[Sourav Poddar]

Hi Kevin,
On Tuesday 23 April 2013 12:06 AM, Kevin Hilman wrote:
> Grygorii Strashko<grygorii.strashko@xxxxxx>  writes:
>
> > On 04/22/2013 04:43 PM, Sourav Poddar wrote:
> > > The driver manages "no_console_suspend" by preventing runtime PM
> > > during the suspend path, which forces the console UART to stay awake.
> > >
> > > Signed-off-by: Sourav Poddar<sourav.poddar@xxxxxx>
> > > ---
> > >    drivers/tty/serial/omap-serial.c |    5 ++++-
> > >    1 files changed, 4 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> > > index 08332f3..640b14e 100644
> > > --- a/drivers/tty/serial/omap-serial.c
> > > +++ b/drivers/tty/serial/omap-serial.c
> > > @@ -1582,7 +1582,7 @@ static int serial_omap_runtime_suspend(struct device *dev)
> > >    	struct uart_omap_port *up = dev_get_drvdata(dev);
> > >    	struct omap_uart_port_info *pdata = dev->platform_data;
> > >    -	if (!up)
> > > +	if (!up || (!console_suspend_enabled&&  uart_console(&up->port)))
> > >    		return -EINVAL;
> > Hi Sourav,
> > No ) You will block Runtime PM for console UART forever, but instead
> > it need to be blocked only during suspend - autosuspend should
> > continue working.
> Correct.
>
> Sourav, as I mentioned when I suggested this approach, it should be done
> *only* during suspend.
Yes, got the point.
> > But this will be not easy, again, -
> > because System suspend isn't synchronized with Runtime PM (I mean,
> > serial_omap_suspend/resume() may be called from one thread and
> > serial_omap_runtime_suspend/resume() from another at same time).
> > And now, serial_omap_suspend() callback is the only one place where you
> > can detect that system is going to sleep.
> So set an 'is_suspending' flag in ->suspend (it may need to be in
> ->prepare) and clear it in ->resume (->complete), and check the flag in
> the ->runtime_supend() callback.  It's not uncommon for drivers to have
> such a flag for various reasons.
Ok. Will adapt the next version inline with the above suggestions.
> > Personally, i don't believe in such approach (my experiences from K3.4
> > said me that there will be more problems than benefits).
> >
> > And, I like combination of "no_console_suspend" in bootargs +
> > "ti,no_idle_on_suspend" for console UART in DT, because 1) it's debug
> > option and 2) until
> > smth. will be decided about OMAP OCP Bus it can be used.
> >
> > It's just my opinion.
> No, we need to get rid of ti,no_idle_on_suspend.  It's an ugly,
> OMAP-specific hack (and I'm free to insult it because I introduced it.)
>
> Kevin

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