Re: [PATCH v4 1/2] arm64: dts: rockchip: add "rockchip, grf" property for RK3399 PMUCRU/CRU

From: "Heiko Stübner" <heiko@sntech.de>
To: Doug Anderson <dianders@google.com>
Cc: Xing Zheng <zhengxing@rock-chips.com>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Caesar Wang <wxt@rock-chips.com>,
	Shawn Lin <shawn.lin@rock-chips.com>,
	Brian Norris <briannorris@chromium.org>,
	Jianqun Xu <jay.xu@rock-chips.com>,
	Elaine Zhang <zhangqing@rock-chips.com>,
	David Wu <david.wu@rock-chips.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 1/2] arm64: dts: rockchip: add "rockchip, grf" property for RK3399 PMUCRU/CRU
Date: Tue, 10 Jan 2017 20:58:10 +0100	[thread overview]
Message-ID: <1523574.hS8CXi1tTP@diego> (raw)
In-Reply-To: <8683375.pL9J7LxuT0@diego>

Hi Doug,

Am Dienstag, 10. Januar 2017, 20:46:12 schrieb Heiko Stübner:
> Am Dienstag, 10. Januar 2017, 10:45:48 schrieb Doug Anderson:
> > Hi,
> > 
> > On Mon, Jan 9, 2017 at 10:15 PM, Xing Zheng <zhengxing@rock-chips.com>
> 
> wrote:
> > > The structure rockchip_clk_provider needs to refer the GRF regmap
> > > in somewhere, if the CRU node has not "rockchip,grf" property,
> > > calling syscon_regmap_lookup_by_phandle will return an invalid GRF
> > > regmap, and the MUXGRF type clock will be not supported.
> > > 
> > > Therefore, we need to add them.
> > > 
> > > Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
> > > ---
> > > 
> > > Changes in v4:
> > > - separte the binding patch
> > > 
> > > Changes in v3:
> > > - add optional roperty rockchip,grf in rockchip,rk3399-cru.txt
> > > 
> > > Changes in v2:
> > > - referring pmugrf for PMUGRU
> > > - fix the typo "invaild" in COMMIT message
> > > 
> > >  arch/arm64/boot/dts/rockchip/rk3399.dtsi | 2 ++
> > >  1 file changed, 2 insertions(+)
> > 
> > This seems fine to me, so:
> > 
> > Reviewed-by: Douglas Anderson <dianders@chromium.org>
> > 
> > ...but I will say that before you actually add any real "MUXGRF"
> > clocks on rk3399 you _might_ need to rework the code to make things
> > truly "optional".  If it turns out that any existing clocks that
> > already exist today already go through one of these muxes in the GRF
> > and we've always been assuming one setting of the mux, we'll need to
> > make sure we keep assuming that setting of the mux even if the "grf"
> > isn't specified.
> 
> I guess I see that a bit more relaxed :-) .
> 
> I.e. the GRF being optional is a remnant of syscons not being available when
> the clocks get set up- so were coming in later or not at all. For the
> rk3288 I converted, there we never really had the case of the GRF missing.
> 
> And the GRF mux for the vcodec now present is not being used by anything yet
> (neither driver nor binding), so no old devicetree can break.
> 
> > As I understand it, your motivation for this patch is to eventually be
> > able to model the EDP reference clock which can either be xin24 or
> > "edp osc".  Presumably the eDP "reference clock" isn't related to any
> > of the pre-existing eDP clocks so that one should be safe.
> 
> Same here, so far we don't even have edp or even any other graphical output
> on the rk3399, so again there is no old devicetree that could break when
> the grf is not specified.

reading all of the above again, it feels like you essentially also said 
similar things already in your original reply and I misread some of it.

But again, I don't see the need for any more code right now, as hopefully the 
simple stuff we currently only support does not have any grf-based muxes in 
it. Xing + Rockchip people, please correct me if I'm wrong here :-)

Heiko