linux-kernel - Re: [PATCH v2 4/6] arm64: dts: rockchip: Add device tree support for HDMI RX Controller

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Message-ID: <ca099-65e8c400-33-2b230d40@237921438>
Date: Wed, 06 Mar 2024 19:28:24 +0000
From: "Shreeya Patel" <shreeya.patel@...labora.com>
To: Heiko Stübner <heiko@...ech.de>
Cc: mchehab@...nel.org, robh@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, mturquette@...libre.com, sboyd@...nel.org, p.zabel@...gutronix.de, jose.abreu@...opsys.com, nelson.costa@...opsys.com, dmitry.osipenko@...labora.com, sebastian.reichel@...labora.com, shawn.wen@...k-chips.com, nicolas.dufresne@...labora.com, hverkuil@...all.nl, hverkuil-cisco@...all.nl, kernel@...labora.com, linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, linux-clk@...r.kernel.org, linux-arm@...ts.infradead.org
Subject: Re: [PATCH v2 4/6] arm64: dts: rockchip: Add device tree support for HDMI RX Controller

On Wednesday, March 06, 2024 01:50 IST, Heiko Stübner <heiko@...ech.de> wrote:

> Hi again :-)
> 
> Am Dienstag, 5. März 2024, 20:05:02 CET schrieb Shreeya Patel:
> > On Tuesday, March 05, 2024 19:41 IST, Heiko Stübner <heiko@...ech.de> wrote:
> > > Am Dienstag, 5. März 2024, 13:36:46 CET schrieb Shreeya Patel:
> > > > Add device tree support for Synopsys DesignWare HDMI RX
> > > > Controller.
> > > > 
> > > > Reviewed-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> > > > Tested-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> > > > Co-developed-by: Dingxian Wen <shawn.wen@...k-chips.com>
> > > > Signed-off-by: Dingxian Wen <shawn.wen@...k-chips.com>
> > > > Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>
> > > > ---
> > > > Changes in v2 :-
> > > >   - Fix some of the checkpatch errors and warnings
> > > >   - Rename resets, vo1-grf and HPD
> > > >   - Move hdmirx_cma node to the rk3588.dtsi file
> > > > 
> > > >  .../boot/dts/rockchip/rk3588-pinctrl.dtsi     | 41 ++++++++++++++
> > > >  arch/arm64/boot/dts/rockchip/rk3588.dtsi      | 55 +++++++++++++++++++
> > > >  2 files changed, 96 insertions(+)
> > > 
> > > > diff --git a/arch/arm64/boot/dts/rockchip/rk3588.dtsi b/arch/arm64/boot/dts/rockchip/rk3588.dtsi
> > > > index 5519c1430cb7..8adb98b99701 100644
> > > > --- a/arch/arm64/boot/dts/rockchip/rk3588.dtsi
> > > > +++ b/arch/arm64/boot/dts/rockchip/rk3588.dtsi
> > > > @@ -7,6 +7,24 @@
> > > >  #include "rk3588-pinctrl.dtsi"
> > > >  
> > > >  / {
> > > > +	reserved-memory {
> > > > +		#address-cells = <2>;
> > > > +		#size-cells = <2>;
> > > > +		ranges;
> > > 
> > > add blank line here
> > > 
> > > > +		/*
> > > > +		 * The 4k HDMI capture controller works only with 32bit
> > > > +		 * phys addresses and doesn't support IOMMU. HDMI RX CMA
> > > > +		 * must be reserved below 4GB.
> > > > +		 */
> > > > +		hdmirx_cma: hdmirx_cma {
> > > 
> > > phandles use "_", but node-names "-"
> > > 
> > > > +			compatible = "shared-dma-pool";
> > > > +			alloc-ranges = <0x0 0x0 0x0 0xffffffff>;
> > > > +			size = <0x0 (160 * 0x100000)>; /* 160MiB */
> > > 
> > > The comment above that node, could elaborate where the value of 160MB
> > > originates from. I assume it is to hold n-times of 4K frames or whatever,
> > > but it would be helpful for people to be able to read that.
> > > 
> > 
> > right, we did the following calculation to come up with this value :-
> > 3840 * 2160 * 4 (bytes/pix) * 2 (frames/buffer) / 1000 / 1000 = 66M
> > and then we do the 2x times of this value to be on the safer side
> > and support all practical use-cases.
> > 
> > I'll add some more details to the comment in v3.
> 
> thanks, that will be helpful for me and everybody reading the dts later on
> 
> > 
> > > 
> > > > +			no-map;
> > > > +			status = "disabled";
> > > > +		};
> > > > +	};
> > > > +
> > > >  	pcie30_phy_grf: syscon@...b8000 {
> > > >  		compatible = "rockchip,rk3588-pcie3-phy-grf", "syscon";
> > > >  		reg = <0x0 0xfd5b8000 0x0 0x10000>;
> > > > @@ -85,6 +103,38 @@ i2s10_8ch: i2s@...00000 {
> > > >  		status = "disabled";
> > > >  	};
> > > >  
> > > > +	hdmi_receiver: hdmi-receiver@...e0000 {
> > > 
> > > Maybe rename the label to "hdmirx:" ... that way in a board enabling the
> > > cma region, both nodes would stay close to each other?
> > > 
> > 
> > Umm we already have receiver in the name so I am not sure if adding rx will be
> > a good idea. I was trying to keep it consistent with the names used in other device tree files.
> > In case you still feel otherwise then do let me know, I'll make the change.
> 
> I'm somewhat partial to the actual name, I was more getting at similar
> names to keep things together.
> 
> General sorting rules are that &foo phandles are sorted alphabetically
> in board devicetrees.
> 
> So having
> 
> &hdmirx {
> 	status = "okay";
> };
> 
> &hdmirx_cma {
> 	status = "okay";
> };
> 
> in the board dt, makes them stay together automatically ;-)
> 
> So if it's hdmirx + hdmirx_cma or hdmi_receiver + hdmi_receiver_cma
> doesn't matter that much, just that they share a common basename.
> 
> 
> I really want to stay away from allowing special rules for things as much
> as possible, because that becomes a neverending story, so it's
> alphabetical sorting.
> 
> But nothing prevents us from naming phandles in an intelligent way ;-) .
> 

Makes sense to me, I'll use hdmi_receiver + hdmi_receiver_cma combination
to keep it consistent.

Thanks,
Shreeya Patel

> 
> Thanks
> Heiko
>