[PATCH] ARM: dts: am335x-pocketbeagle: choose tick-timer

[Trevor Woerner]

On Fri 2023-09-08 @ 12:36:17 PM, Nishanth Menon wrote:
> On 11:25-20230830, Trevor Woerner wrote:
> > Commit 4b2be78ab66c ("time: Fix get_ticks being non-monotonic")
> > requires '/chosen/tick-timer' in device-tree. Otherwise we get:
> > 
> > 	U-Boot 2023.07.02 (Jul 11 2023 - 15:20:44 +0000)
> > 
> > 	CPU  : AM335X-GP rev 2.1
> > 	Model: TI AM335x PocketBeagle
> > 	DRAM:  512 MiB
> > 	Core:  154 devices, 16 uclasses, devicetree: separate
> > 	Could not initialize timer (err -19)
> > 
> > 	resetting ...
> > 
> > Suggested-by: Pierre Lebleu <pierre.lebleu at pile-engineering.com>
> > Signed-off-by: Trevor Woerner <twoerner at gmail.com>
> > ---
> >  arch/arm/dts/am335x-pocketbeagle.dts | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/arm/dts/am335x-pocketbeagle.dts b/arch/arm/dts/am335x-pocketbeagle.dts
> > index b379e3a5570d..02e3aac56064 100644
> > --- a/arch/arm/dts/am335x-pocketbeagle.dts
> > +++ b/arch/arm/dts/am335x-pocketbeagle.dts
> > @@ -15,6 +15,7 @@
> >  
> >  	chosen {
> >  		stdout-path = &uart0;
> > +		tick-timer = &timer2;
> >  	};
> >  
> >  	leds {
> > -- 
> > 2.41.0.327.gaa9166bcc0ba
> > 
> 
> Does enabling CONFIG_SYS_ARCH_TIMER solve this?

Enabling CONFIG_SYS_ARCH_TIMER causes the following compile error:

	| arm-oe-linux-gnueabi-ld.bfd: arch/arm/cpu/armv7/arch_timer.o: in function `timer_init':
	| /z/build-master/pocketbeagle/build/tmp-glibc/work/pocketbeagle-oe-linux-gnueabi/u-boot/2023.07.02/git/arch/arm/cpu/armv7/arch_timer.c:29: multiple definition of `timer_init'; arch/arm/mach-omap2/timer.o:/z/build-master/pocketbeagle/build/tmp-glibc/work/pocketbeagle-oe-linux-gnueabi/u-boot/2023.07.02/git/arch/arm/mach-omap2/timer.c:44: first defined here
	| arm-oe-linux-gnueabi-ld.bfd: arch/arm/cpu/armv7/arch_timer.o: in function `get_ticks':
	| /z/build-master/pocketbeagle/build/tmp-glibc/work/pocketbeagle-oe-linux-gnueabi/u-boot/2023.07.02/git/arch/arm/cpu/armv7/arch_timer.c:44: multiple definition of `get_ticks'; arch/arm/mach-omap2/timer.o:/z/build-master/pocketbeagle/build/tmp-glibc/work/pocketbeagle-oe-linux-gnueabi/u-boot/2023.07.02/git/arch/arm/mach-omap2/timer.c:97: first defined here
	| arm-oe-linux-gnueabi-ld.bfd: arch/arm/cpu/armv7/arch_timer.o: in function `get_tbclk':
	| /z/build-master/pocketbeagle/build/tmp-glibc/work/pocketbeagle-oe-linux-gnueabi/u-boot/2023.07.02/git/arch/arm/cpu/armv7/arch_timer.c:63: multiple definition of `get_tbclk'; arch/arm/mach-omap2/timer.o:/z/build-master/pocketbeagle/build/tmp-glibc/work/pocketbeagle-oe-linux-gnueabi/u-boot/2023.07.02/git/arch/arm/mach-omap2/timer.c:108: first defined here

Without CONFIG_SYS_ARCH_TIMER, the functions timer_init(), get_ticks(), and
get_tbclk() are defined in arch/arm/mach-omap2/timer.c. When
CONFIG_SYS_ARCH_TIMER is defined, it also pulls in the file
arch/arm/cpu/armv7/arch_timer.c.

There is a config option, CONFIG_TIMER, that controls the inclusion of
arch/arm/mach-omap2/timer.c, but it is unconditional during SPL:

	arch/arm/mach-omap2/Makefile
	...
	 12 ifeq ($(CONFIG_TIMER),)
	 13 obj-y   += timer.o
	 14 else
	 15 ifdef CONFIG_SPL_BUILD
	 16 obj-y   += timer.o
	 17 endif
	 18 endif
	...

So whether CONFIG_TIMER is defined or not, a compile error will result if
CONFIG_SYS_ARCH_TIMER is also defined.

Getting the code to compile with CONFIG_SYS_ARCH_TIMER would require a deeper
reworking of the configuration/Make logic in order to swap out the functions
in arch/arm/mach-omap2/timer.c for the ones in
arch/arm/cpu/armv7/arch_timer.c. The definitions of those functions in both
those locations are quite different, so even after getting the build to work
there's no guarantee the arch functions would work.

Best regards,
	Trevor