Re: ABE/AESS on modern kernel: clocks, hwmods etc.

[Tony Lindgren <tony@atomide.com>]

* H. Nikolaus Schaller <hns@goldelico.com> [230904 18:07]:
> > Am 04.09.2023 um 08:34 schrieb Tony Lindgren <tony@atomide.com>:
> > No idea about this one, but this might be doable with generic pwm code
> > now with the dmtimers. See for example how the ir-rx51 is getting phased
> > away and replaced with the generci pwm ir driver.
> 
> This is not PWM. It writes to some register shared with the AESS DSP and we assume that the
> DSP firmware should be started. I have put Péter on CC, maybe he knows something.

Hmm sorry I somehow thought it was using a dmtimer. There are references to
ABE_GPT5_FCLK to ABE_GPT8_FCLK in the TRM but maybe those are separate
and the driver is not tinkering with the timer register directly hopefully.

> >>> It seems as if clocks and code like omap_hwmod_aess_preprogram() is missing. Especially for the
> >>> omap4 we have found no equivalent to aess_fclk which exists for omap5 and dra7.
> >>> Nowhere is a reference using the abe_iclk node.
> >>> 
> >> for omap4 I guess the 
> >>                        clocks = <&abe_clkctrl OMAP4_AESS_CLKCTRL 0>;
> >> 
> >> in omap4-l4-abe.dtsi should be enough and correcly referencing fclk?
> > 
> > Yeah the clocks chould be there and should use addressing like Andreas is
> > showing.
> 
> Well, according to my analysis the fclk may be there but the iclk is missing or not initialized.
> That could explain why we get L3 problems as soon as we try to start the AESS-DSP.

OK

> The key observation is that the abe_iclk references in the DTS seem to be nowhere referenced
> (which may or may not be an issue):
>
> https://github.com/goldelico/letux-kernel/blob/letux/aess-v12/arch/arm/boot/dts/ti/omap/omap44xx-clocks.dtsi#L509
> https://github.com/goldelico/letux-kernel/blob/letux/aess-v12/arch/arm/boot/dts/ti/omap/omap54xx-clocks.dtsi#L161

So I guess the ick is in the dts the ocp_abe_iclk@528 for omap4 and
abe_iclk@528 for omap5. Seems like the driver should request them, I recall
that the interconnect target module does not need the ick to access sysc
and revision registers.

> The branch where all changes are sitting can be inspected here:
> 
> https://github.com/goldelico/letux-kernel/commits/letux/aess-v12?after=567e9011a67f4ed0824c2989a5d5f73ca0139461+63&branch=letux%2Faess-v12&qualified_name=refs%2Fheads%2Fletux%2Faess-v12
> 
> They are all tagged ARM: DTS: omap4 or omap5.

Hmm the "we don't need separate target modules" patch is wrong, the modules
may have separate clocks and power domains, and flushing a posted write to
one module does not flush write to the other module. This can lead into hard
to track down bugs accessing separate modules. The dts module data I
generated from the hardware AP registers for each SoC so the module ranges
should be correct.

> Hope this helps. Otherwise we have to prepare a cleaned up version of the DTS changes as a patch series.

Yeah nice,

Tony