[PATCH] bus: ti-sysc: Fix gpt12 system timer issue with reserved status

[Kevin Hilman]

Hi Tony,

Tony Lindgren <tony at atomide.com> writes:

> Jarkko Nikula <jarkko.nikula at bitmer.com> reported that Beagleboard
> revision c2 stopped booting. Jarkko bisected the issue down to
> commit 6cfcd5563b4f ("clocksource/drivers/timer-ti-dm: Fix suspend
> and resume for am3 and am4").
>
> Let's fix the issue by tagging system timers as reserved rather than
> ignoring them. And let's not probe any interconnect target module child
> devices for reserved modules.
>
> This allows PM runtime to keep track of clocks and clockdomains for
> the interconnect target module, and prevent the system timer from idling
> as we already have SYSC_QUIRK_NO_IDLE and SYSC_QUIRK_NO_IDLE_ON_INIT
> flags set for system timers.
>
> Fixes: 6cfcd5563b4f ("clocksource/drivers/timer-ti-dm: Fix suspend and resume for am3 and am4")
> Reported-by: Jarkko Nikula <jarkko.nikula at bitmer.com>
> Signed-off-by: Tony Lindgren <tony at atomide.com>

I'm debugging why suspend/resume on AM3x and AM4x are mostly working,
but getting the warning that not all powerdomains are transitioning:

   pm33xx pm33xx: PM: Could not transition all powerdomains to target state

I bisected it down to $SUBJECT patch, and verified that reverting it
makes both on am335x-boneblack and am437x-gp-evm fully suspend, and I'm
now seeing:

   pm33xx pm33xx: PM: Successfully put all powerdomains to target state

Note that it doesn't revert cleanly due to some other changes, but this
one-liner[1] effectively reverts the behavior of $SUBJECT patch, and
also makes things work again.

I verified the revert (and hack[1]) on both v5.10 stable and mainline
v5.16 but TBH, I'm still not 100% sure what's going on so looking for
some guidance from you Tony on what the "real" fix should be.

Kevin

[1] 
diff --git a/drivers/bus/ti-sysc.c b/drivers/bus/ti-sysc.c                                                                                                            
index 54c0ee6dda30..82379ff9dce5 100644                                                                                                                               
--- a/drivers/bus/ti-sysc.c                                                                                                                                           
+++ b/drivers/bus/ti-sysc.c                                                                                                                                           
@@ -3304,7 +3304,7 @@ static int sysc_probe(struct platform_device *pdev)                                                                                             
                                                                                                                                                                      
        error = sysc_check_active_timer(ddata);                                                                                                                       
        if (error == -ENXIO)                                                                                                                                          
-               ddata->reserved = true;                                                                                                                               
+               return error;                                                                                                                                         
        else if (error)                                                                                                                                               
                return error;