Re: [PATCHv3] driver: serial: prevent UART console idle on suspendwhile using "no_console_suspend"

[Sourav Poddar]

Hi,
On Wednesday 10 April 2013 12:37 AM, Kevin Hilman wrote:
> Sourav Poddar<sourav.poddar@xxxxxx>  writes:
>
> > Hi Kevin,
> > On Friday 05 April 2013 11:10 PM, Kevin Hilman wrote:
> > > Sourav Poddar<sourav.poddar@xxxxxx>   writes:
> > >
> > > > With dt boot, uart wakeup after suspend is non functional while using
> > > > "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
> > > > should prevent the runtime suspend of the uart port which is getting used
> > > > as an console.
> > > >
> > > > Cc: Santosh Shilimkar<santosh.shilimkar@xxxxxx>
> > > > Cc: Felipe Balbi<balbi@xxxxxx>
> > > > Cc: Rajendra nayak<rnayak@xxxxxx>
> > > > Tested on omap5430evm, omap4430sdp.
> > > >
> > > > Signed-off-by: Sourav Poddar<sourav.poddar@xxxxxx>
> > > Rather than make these special checks inside the driver's runtime PM
> > > callbacks, you should just disable runtime PM (pm_runtime_disable())
> > >
> > > Then, this should be broken into 2 patches.
> > >
> > > 1) serial core: add the '->is_console' flag.  (nit on naming: don't call
> > >      it port_is_console, since the struct is already a uart_port)
> > >
> > > 2) In the OMAP UART driver's ->prepare callback, check the is_console flag
> > >      and pm_runtime_disable() accordingly  (then pm_runtime_enable() in
> > >      the drivers's ->complete callback.
> > >
> > > Kevin
> > I was working on your above suggestions, but realised there is not
> > only console
> > uart which has the requirement of keeping the clocks enabled while going on
> > suspend.
> >
> > If you see arch/arm/boot/dts/am33xx.dtsi, there is a ocmcram which has
> > "no_idle_on_suspend" property used.
> Can you please ask the AM33xx folks how (and why) this is being used?
>
> I don't see/find a driver for this device in mainline, so without a
> driver this flag will not be used.
Looping in Vaibhav Bedia for ocmcram..

[Vaibhav]:
  There is a discussion going on about a cleaner way of handling
  ti, no_idle_on_suspend" part (as this is a sort of hack). We got a way
  around for UART ($subject) by making serial core/driver handle this 
for us.
  But with this, we will delete codes around "no_idle_on_suspend" flag in
  omap_device file.

  But, we realised that its not only UART which requires the clocks to 
be active
  whie going for suspend. There is a dts entry for ocmcram also.

  As Kevin also pointed out, we don't see a driver for this device in 
mainline, It would be
  great if you can explain how its getting used?

  You can find the complete discussion on v3 here:
     https://lkml.org/lkml/2013/4/5/239

> >      ocmcram: ocmcram@40300000 {
> >                          compatible = "ti,am3352-ocmcram";
> >                          reg =<0x40300000 0x10000>;
> >                          ti,hwmods = "ocmcram";
> >                          ti,no_idle_on_suspend;
> >          };
> > This property gets checked in omap_device file and correspondingly
> > od->flags is set.
> >
> > Based on your above inputs, the patches which I cooked up is
> > inlined[1]. Though, the below
> > patches works fine for uart case. The patches will effect ocmcram case
> > and I am inling them
> > "just for discussion".
> Could you also have a look at Russell's suggestion for getting rid of
> the 'is_console' flag.
[Kevin]: Yes, will do that.
> Thanks,
>
> Kevin
~Sourav
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