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

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: "Heiko Stübner" <heiko@sntech.de>
Cc: "Mylène Josserand" <mylene.josserand@collabora.com>,
	"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: Fri, 6 Mar 2020 11:45:25 +0100	[thread overview]
Message-ID: <CAMuHMdXJQqaCcMko9GUAeUiYQzmy3vnX42yVQNPzhj5ijtFuYA@mail.gmail.com> (raw)
In-Reply-To: <2221545.2vEflg7qi2@diego>

Hi Heiko,

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.

> (2) I guess the rk3288w will not be the last soc doing this and on arm64 you
>     can't do it that way, as there is no mach-rockchip there

There's drivers/soc/rockchip ;-)

> So my personal preference would really would be just a specific compatible
> for affected ip blocks.

Doing that only for affected IP blocks may miss integration differences.
Of course, you can always resort to soc_device_match() to handle those...

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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