Re: [PATCH v6 00/12] ARM/MIPS: DTS: add child nodes describing the PVRSGX GPU present in some OMAP SoC and JZ4780 (and many more)
From: Tony Lindgren
Date: Tue Apr 21 2020 - 13:39:48 EST
* H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> [200421 17:31]:
> > Am 21.04.2020 um 16:15 schrieb Tony Lindgren <tony@xxxxxxxxxxx>:
> > Note that on omaps there are actually SoC module specific registers.
>
> Ah, I see. This is of course a difference that the TI glue logic has
> its own registers in the same address range as the sgx and this can't
> be easily handled by a common sgx driver.
>
> This indeed seems to be unique with omap.
>
> > And there can be multiple devices within a single target module on
> > omaps. So the extra dts node and device is justified there.
> >
> > For other SoCs, the SGX clocks are probably best handled directly
> > in pvr-drv.c PM runtime functions unless a custom hardware wrapper
> > with SoC specific registers exists.
>
> That is why we need to evaluate what the better strategy is.
>
> So we have
> a) omap which has a custom wrapper around the sgx
> b) others without, i.e. an empty (or pass-through) wrapper
>
> Which one do we make the "standard" and which one the "exception"?
> What are good reasons for either one?
The wrapper is already handled by the ti-sysc binding, the sgx
binding should be standard with optional clocks.
See for example the standard 8250 uart for am335x with:
$ git grep -B20 -A10 uart0 arch/arm/boot/dts/am33xx-l4.dtsi
The 8250 device configuration is described in the standard 8250
dts binding, and the am335x module in the ti-sysc binding.
The are separate devices :)
So for the sgx binding, you can just leave out TI specific
module wrapper completely from the example.
> It also allows to handle different number of clocks (A31 seems to
> need 4, Samsung, A83 and JZ4780 one) without changing the sgx bindings
> or making big lists of conditionals. This variance would be handled
> outside the sgx core bindings and driver.
Well if other SoCs implement genpd domains etc, that's then
again part of a separate binding and not part of the sgx binding.
Regards,
Tony