Re: [PATCH] Input: pm8941-pwrkey - respect reboot_mode for warm reset

[Luca Weiss <luca@z3ntu.xyz>]

Hi Shawn,

On Mittwoch, 14. Juli 2021 11:40:46 CET Shawn Guo wrote:
> Hi Luca,
> 
> On Sun, Jul 11, 2021 at 11:57:25AM +0200, Luca Weiss wrote:
> > Hi Shawn,
> > 
> > On Dienstag, 29. Juni 2021 05:05:09 CEST Shawn Guo wrote:
> > > On some devices, e.g. Sony Xperia M4 Aqua, warm reset is used to reboot
> > > device into bootloader and recovery mode.  Instead of always doing hard
> > > reset, add a check on reboot_mode for possible warm reset.
> > > 
> > > Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> > > ---
> > > 
> > >  drivers/input/misc/pm8941-pwrkey.c | 6 +++++-
> > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/input/misc/pm8941-pwrkey.c
> > > b/drivers/input/misc/pm8941-pwrkey.c index cf8104454e74..9b14d6eb1918
> > > 100644
> > > --- a/drivers/input/misc/pm8941-pwrkey.c
> > > +++ b/drivers/input/misc/pm8941-pwrkey.c
> > > @@ -27,6 +27,7 @@
> > > 
> > >  #define PON_PS_HOLD_RST_CTL2		0x5b
> > >  #define  PON_PS_HOLD_ENABLE		BIT(7)
> > >  #define  PON_PS_HOLD_TYPE_MASK		0x0f
> > > 
> > > +#define  PON_PS_HOLD_TYPE_WARM_RESET	1
> > > 
> > >  #define  PON_PS_HOLD_TYPE_SHUTDOWN	4
> > >  #define  PON_PS_HOLD_TYPE_HARD_RESET	7
> > > 
> > > @@ -93,7 +94,10 @@ static int pm8941_reboot_notify(struct notifier_block
> > > *nb, break;
> > > 
> > >  	case SYS_RESTART:
> > > 
> > >  	default:
> > > -		reset_type = PON_PS_HOLD_TYPE_HARD_RESET;
> > > +		if (reboot_mode == REBOOT_WARM)
> > 
> > This doesn't compile with CONFIG_INPUT_PM8941_PWRKEY=m
> > 
> >  ERROR: modpost: "reboot_mode" [drivers/input/misc/pm8941-pwrkey.ko]
> >  undefined!
> Thanks for the report!  I will add a patch to export the symbol.
> 
> > Also just to clarify, this is supposed to trigger when rebooting with
> > LINUX_REBOOT_CMD_RESTART2 and adding an argument that way, right?
> 
> With either of the following two methods, 'reboot_mode' will be turned
> into REBOOT_WARM.
> 
> - Boot kernel with 'reboot=warm' on cmdline
> 
> - Set warm mode via sysfs entry
>   $ echo warm > /sys/kernel/reboot/mode

+CC Sebastian Reichel

Do you have an idea how this situation should look from user space? Just using 
LINUX_REBOOT_CMD_RESTART2 with the param won't work if the reboot mode also 
has to be set to work - but that's also not the case on all boards.

Just LINUX_REBOOT_CMD_RESTART2 works fine on newer qcom SoCs that iirc store it 
in a pmic register that seems to survive a hard reboot.

Would it be a good idea to introduce a new dt property for e.g.
syscon-reboot-mode that makes it switch to warm reboot mode when a reboot mode 
is passed to the kernel? That way user space wouldn't need to care whether a 
particular board needs warm reboot or can just use the default hard reboot.

Regards
Luca

> Shawn