[U-Boot] [PATCH 1/3] ARmv7: Add a soc_init hook to start.S

[Tom Rini]

On Mon, Jan 26, 2015 at 08:32:41PM +0100, Hans de Goede wrote:
> Hi,
> 
> On 26-01-15 16:18, Tom Rini wrote:
> >On Fri, Jan 23, 2015 at 09:54:12AM +0100, Hans de Goede wrote:
> >>Hi,
> >>
> >>On 22-01-15 22:03, Tom Rini wrote:
> >>>On Thu, Jan 22, 2015 at 08:10:06PM +0100, Hans de Goede wrote:
> >>>>Hi,
> >>>>
> >>>>On 22-01-15 17:20, Tom Rini wrote:
> >>>>>On Wed, Jan 21, 2015 at 09:03:25PM +0100, Hans de Goede wrote:
> >>>>>
> >>>>>>On some SoCs / ARMv7 CPU cores we need to do some setup before enabling the
> >>>>>>icache, etc. Add a soc_init hook with a weak default which just calls
> >>>>>>cpu_init_cp15.
> >>>>>>
> >>>>>>This way different implementations can be provided to do some extra work
> >>>>>>before or after cpu_init_cp15, or completely replacing cpu_init_cp15.
> >>>>>>
> >>>>>>Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> >>>>>>---
> >>>>>>  arch/arm/cpu/armv7/start.S | 18 +++++++++++++++++-
> >>>>>>  1 file changed, 17 insertions(+), 1 deletion(-)
> >>>>>>
> >>>>>>diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> >>>>>>index fdc05b9..9882b20 100644
> >>>>>>--- a/arch/arm/cpu/armv7/start.S
> >>>>>>+++ b/arch/arm/cpu/armv7/start.S
> >>>>>>@@ -64,7 +64,7 @@ reset:
> >>>>>>
> >>>>>>  	/* the mask ROM code should have PLL and others stable */
> >>>>>>  #ifndef CONFIG_SKIP_LOWLEVEL_INIT
> >>>>>>-	bl	cpu_init_cp15
> >>>>>>+	bl	soc_init
> >>>>>>  	bl	cpu_init_crit
> >>>>>>  #endif
> >>>>>
> >>>>>I like the direction here.  And I want to make sure I get the sunxi
> >>>>>direction right here too (as I agree with the need / desire for boot0 +
> >>>>>U-Boot to be a valid combination).  I think we can take this a step
> >>>>>farther.  cpu_init_crit (on armv7) is basically a call to s_init().
> >>>>>
> >>>>>For am33xx (and I bet but need to do and test omap3+) we can, with
> >>>>>Simon's patch to let us move stack to DDR a tiny bit later, in the SPL
> >>>>>case make s_init empty, which just leaves us with (with your patch)
> >>>>>soc_init.  Is there some way we can put all of this together in a
> >>>>>function?
> >>>>
> >>>>You mean essentially call s_init here and have s_init call cpu_init_cp15
> >>>>I guess we could do that, but it would require auditing all existing armv7
> >>>>users of s_init. This may require me to rethink how / when I do timer &
> >>>>gpio init etc. for u-boot.bin on sunxi, but that should not be a (big)
> >>>>problem.
> >>>
> >>>Basically.  From my first pass audit of s_init, it's either empty
> >>>(Kona), sunxi, or omap/etc so I get to deal with it.  And the default
> >>>soc_init would just be the call to cpu_init_cp15 as you have it and we
> >>>drop the lowlevel_init hurdles.
> >>
> >>Ok, so what you're suggesting is a patch which:
> >>
> >>1) Changes:
> >>
> >>#ifndef CONFIG_SKIP_LOWLEVEL_INIT
> >>	bl	cpu_init_cp15
> >>    	bl	cpu_init_crit
> >>#endif
> >>
> >>Into:
> >>
> >>#ifndef CONFIG_SKIP_LOWLEVEL_INIT
> >>	bl	lowlevel_init
> >>#endif
> >>
> >>Which will setup the stack and then call the s_init C function
> >>
> >>2) Adds a weak default s_init which calls cpu_init_cp15
> >>
> >>3) Patch all existing s_init functions to call cpu_init_cp15
> >>before doing anything else.
> >
> >Pretty close.  Simon's SPL DM series and related clean-ups got me
> >thinking that yes, seemingly too much got shoved into "s_init" that
> >really could have been done using an existing hook done slightly later.
> >
> >>And then in follow up patches we can:
> >>
> >>4) Drop cpu_init_crit
> >>
> >>5) Cleanup some s_init functions (this will be left to the individual
> >>SoC maintainers)
> >>
> >>I think that is a good idea, Albert what do you think about this ?
> >
> >So I'd like to see 5 done "soon" afterwards as it's me (omap*) and
> >sunxi.  I think we can simplfy the call sequence too, to roughly:
> >#ifndef CONFIG_SKIP_LOWLEVEL_INIT
> >     ... Set up stack for C, it's just a few instrs
> >     bl lowlevel_init
> >#endif
> >     bl _main
> >
> >__weak asm
> >lowlevel_init:
> >   bl cpu_init_cp15
> >   return to caller
> >
> >And comment that anything called via lowlevel_init must be C-callable.
> >I hope that once #5 is done no one actually has a lowlevel_init that's
> >done in C but we've kept the door open should it be needed down the
> >road (as I _think_ we can shuffle both the omap* and sunxi stuff to do
> >their inits as needed in both SPL and full U-Boot from an early hook in
> >board_init_r, top of my head is board_init calls some_other_func() in
> >full U-Boot to ensure GPIOs, etc, on sunxi and spl_board_init() calls
> >same func in SPL, and we can consolidate again further down the road as
> >we get SPL and full U-Boot more in sync on the call chain).
> 
> Sounds good to me, and I'm fine with working the sunxi side of things.
> 
> Since you seem to have this all in your head can you do a patch for this
> replacing my patchset ?

I suppose that's what happens when you have a detailed plan, will do ;)

-- 
Tom
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