linux-kernel - Re: [PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl property

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8a2b1876-d1d4-4523-ae6a-bd14875772cf@bootlin.com>
Date: Thu, 31 Jul 2025 11:50:16 +0200
From: Louis Chauvet <louis.chauvet@...tlin.com>
To: Rob Herring <robh@...nel.org>
Cc: Jyri Sarha <jyri.sarha@....fi>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Sam Ravnborg <sam@...nborg.org>,
 Benoit Parrot <bparrot@...com>, Lee Jones <lee@...nel.org>,
 Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Tero Kristo <kristo@...nel.org>, thomas.petazzoni@...tlin.com,
 Jyri Sarha <jsarha@...com>, Tomi Valkeinen <tomi.valkeinen@...com>,
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 stable@...r.kernel.org
Subject: Re: [PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl
 property



Le 31/07/2025 à 02:17, Rob Herring a écrit :
> On Wed, Jul 30, 2025 at 07:02:46PM +0200, Louis Chauvet wrote:
>> For am62 processors, we need to use the newly created clk-ctrl property to
>> properly handle data edge sampling configuration. Add them in the main
>> device tree.
>>
>> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
>> Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
>> ---
>>
>> Cc: stable@...r.kernel.org
>> ---
>>   arch/arm64/boot/dts/ti/k3-am62-main.dtsi | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>> index 9e0b6eee9ac77d66869915b2d7bec3e2275c03ea..d3131e6da8e70fde035d3c44716f939e8167795a 100644
>> --- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>> +++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>> @@ -76,6 +76,11 @@ audio_refclk1: clock-controller@...4 {
>>   			assigned-clock-parents = <&k3_clks 157 18>;
>>   			#clock-cells = <0>;
>>   		};
>> +
>> +		dss_clk_ctrl: dss_clk_ctrl@...0 {
>> +			compatible = "ti,am625-dss-clk-ctrl", "syscon";
>> +			reg = <0x8300 0x4>;
> 
> H/w blocks are rarely only 4 bytes of registers... Does this belong to
> some larger block. The problem with bindings defining single registers
> like this is they don't get defined until needed and you have a constant
> stream of DT updates.

In this case, I don't think there is a "larger block". This register 
exists only because TI had issues in the display controller [1].

Here is the extract of MMR registers ([2], page 4311):

[...]
A2E4h AUDIO_REFCLK1_CTRL_PROXY <unrelated>
A300h DPI0_CLK_CTRL_PROXY <this register, 32 bits>
<nothing between 0xA304 and 0xA319>
A320h DSS_DISPC0_CLKSEL1_PROXY <an other dss clock stuff, 32 bits>
A330h MCASP0_CLKSEL_PROXY <unrelated>
[...]

I agree that DSS_DISPC_CLKSEL_PROXY is also related to DSS clock stuff, 
so may be included in the same block, but there is also a big hole in 
between. What do you think is better?

[1]:https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1228207/am62a7-rgb-display-flickering-and-pixel-issue/4687209#4687209
[2]:https://www.ti.com/lit/ug/spruiv7b/spruiv7b.pdf#page=4311

>> +		};
>>   	};
>>   
>>   	dmss: bus@...00000 {
>> @@ -787,6 +792,7 @@ dss: dss@...00000 {
>>   			 <&k3_clks 186 2>;
>>   		clock-names = "fck", "vp1", "vp2";
>>   		interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
>> +		ti,clk-ctrl = <&dss_clk_ctrl>;
>>   		status = "disabled";
>>   
>>   		dss_ports: ports {
>>
>> -- 
>> 2.50.1
>>

-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com