Re: [PATCH 1/2] ARM: Rockchip: Handle rk3288/rk3288w revision

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Mylene Josserand <mylene.josserand@collabora.com>
Cc: "Heiko Stübner" <heiko@sntech.de>,
	"Stephen Boyd" <sboyd@kernel.org>,
	"Michael Turquette" <mturquette@baylibre.com>,
	"Russell King" <linux@armlinux.org.uk>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	"Collabora Kernel ML" <kernel@collabora.com>,
	linux-clk <linux-clk@vger.kernel.org>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/2] ARM: Rockchip: Handle rk3288/rk3288w revision
Date: Thu, 26 Mar 2020 16:31:38 +0100	[thread overview]
Message-ID: <CAMuHMdVKFT7eNK0RUi3miJ08O9FMAVs5Qz=YmbHH5-9UUzLNPw@mail.gmail.com> (raw)
In-Reply-To: <5802ec08-5e6a-8547-ee8e-dde630791235@collabora.com>

Hi Mylene,

On Thu, Mar 26, 2020 at 2:50 PM Mylene Josserand
<mylene.josserand@collabora.com> wrote:
> On 3/6/20 11:45 AM, Geert Uytterhoeven wrote:
> > On Wed, Mar 4, 2020 at 12:00 PM Heiko Stübner <heiko@sntech.de> wrote:
> >> Am Montag, 2. März 2020, 16:57:02 CET schrieb Mylène Josserand:
> >>> Determine which revision of rk3288 by checking the HDMI version.
> >>> According to the Rockchip BSP kernel, on rk3288w, the HDMI
> >>> revision equals 0x1A which is not the case for the rk3288 [1].
> >>>
> >>> As these SOC have some differences, the new function
> >>> 'soc_is_rk3288w' will help us to know on which revision
> >>> we are.
> >>
> >> what happened to just having a different compatible in the dts?
> >> Aka doing a
> >>
> >> rk3288w.dtsi with
> >>
> >> #include "rk3288.dtsi"
> >>
> >> &cru {
> >>          compatible = "rockchip,rk3288w-cru";
> >> }
> >>
> >> I somehow don't expect boards to just switch between soc variants
> >> on the fly.
> >>
> >> Also, doing things in mach-rockchip is not very future-proof:
> >>
> >> (1) having random soc-specific APIs spanning the kernel feels wrong,
> >>      especially as at some point it might not be contained to our own special
> >>      drivers like the cru. I cannot really see people being enthusiastic if
> >>      something like this would be needed in say the core Analogix-DP bridge ;-)
> >
> > Indeed.  You're better of registering an soc_device_attribute using
> > soc_device_register(), after which any driver can use soc_device_match()
> > to differentiate based on the SoC revision.
>
> Thank you for this suggestion. The issue is that clocks are registered
> at an early stage of the boot so using initcalls is too late for the
> clock differentiation :(

IC, rk388 is still using CLK_OF_DECLARE().
What about converting it to a platform driver, registered from e.g.
subsys_initcall()?
If you need some clocks early (e.g. for timers), you can do split
registration, with the early part still using CLK_OF_DECLARE().
That should work, assumed the timer clocks don't need differentiation.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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