linux-kernel - Re: [PATCH 01/11] dt-bindings: display: meson-dw-hdmi: Add compatible for S4 HDMI controller

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Message-Id: <7703796D-35D4-4AD2-B7F8-B75D2BE0F7AD@gmail.com>
Date: Wed, 19 Nov 2025 11:27:26 +0100
From: Piotr Oniszczuk <piotr.oniszczuk@...il.com>
To: Chuan Liu <chuan.liu@...ogic.com>
Cc: ao.xu@...ogic.com,
 Neil Armstrong <neil.armstrong@...aro.org>,
 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>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Kevin Hilman <khilman@...libre.com>,
 Jerome Brunet <jbrunet@...libre.com>,
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 dri-devel@...ts.freedesktop.org,
 linux-amlogic@...ts.infradead.org,
 devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] dt-bindings: display: meson-dw-hdmi: Add compatible
 for S4 HDMI controller

Pls see inline

> Wiadomość napisana przez Chuan Liu <chuan.liu@...ogic.com> w dniu 19 lis 2025, o godz. 03:57:
> 
> Hi Piotr,
> 
> 
> On 11/18/2025 10:50 PM, Piotr Oniszczuk wrote:
>> [You don't often get email from piotr.oniszczuk@...il.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>> [ EXTERNAL EMAIL ]
>> Ao,
>> Is there any chance to get this s4 drm hdmi series for current 6.18?
>> (i tried backport this series to 6.18 but have some issues with reparent vpu_0_sel to sysclk_b_sel)
> 
> Why do we need to reparent vpu_0_sel to sysclk_b_sel? is there any
> background here?

Well - it looks it is because bug....
Martin Blumenstingl had perfect eye and catch typo in patch https://lore.kernel.org/all/20250110-drm-s4-v1-11-cbc2d5edaae8@amlogic.com/:

By replacing:
assigned-clock-parents = <&clkc_periphs CLKID_FCLK_DIV3>,
<0>, /* Do Nothing */
<&clkc_periphs CLKID_VPU_0>,
<&clkc_periphs CLKID_FCLK_DIV4>,
<0>, /* Do Nothing */
<&clkc_periphs CLKID_VAPB_0>;

with:
assigned-clock-parents = <&clkc_pll CLKID_FCLK_DIV3>,
<0>, /* Do Nothing */
<&clkc_periphs CLKID_VPU_0>,
<&clkc_pll CLKID_FCLK_DIV4>,
<0>, /* Do Nothing */
<&clkc_periphs CLKID_VAPB_0>;

dmesg is like this https://termbin.com/6020

So i'm getting hdmi working - but only when device boots _without_ connected hdmi at boot (and connected later)
If hdmi is connected at boot - boot hangs at:

    0.341676] meson-dw-hdmi fe300000.hdmi-tx: Detected HDMI TX controller v2.01a with HDCP (meson_dw_hdmi_phy)
[    0.342750] meson-dw-hdmi fe300000.hdmi-tx: registered DesignWare HDMI I2C bus driver
[    0.343660] meson-drm ff000000.vpu: bound fe300000.hdmi-tx (ops meson_dw_hdmi_ops)
[    0.344832] [drm] Initialized meson 1.0.0 for ff000000.vpu on minor 0

FYI: It is after applying https://patchwork.kernel.org/project/linux-amlogic/cover/20250110-drm-s4-v1-0-cbc2d5edaae8@amlogic.com/ on mainline 6.18 (with some my adjustments on this series required by changes in 6.18). 
For VPU clk changes see https://github.com/warpme/minimyth2/blob/master/script/kernel/linux-6.18/files/0312-drm-meson-add-vpu-clk-setting-for-S4.patch 
It is 6.18 adaptation of https://patchwork.kernel.org/project/linux-amlogic/patch/20250110-drm-s4-v1-9-cbc2d5edaae8@amlogic.com/

As kernel hangs - i have limited caps to drill where root cause is. 

Maybe above hang is reason of my backports or missing any pre-req required to get s4 drm working?
Anyway - it will be good to test with updated to 6.18 series of Add DRM support for Amlogic S4 (plus info about any pre-req required to get s4 drm working)   

> 
> The vpu_clk on S4 doesn't support sysclk_b_sel as one of its
> selectable clock sources, so this reparent operation will definitely
> fail. This has nothing to do with the kernel version.
> 
>>> Wiadomość napisana przez Ao Xu via B4 Relay <devnull+ao.xu.amlogic.com@...nel.org> w dniu 10 sty 2025, o godz. 06:39:
>>> 
>>> From: Ao Xu <ao.xu@...ogic.com>
>>> 
>>> Add devicetree document for S4 HDMI controller
>>> 
>>> Signed-off-by: Ao Xu <ao.xu@...ogic.com>
>>> ---
>>> Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.yaml | 1 +
>>> 1 file changed, 1 insertion(+)
>>> 
>>> diff --git a/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.yaml b/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.yaml
>>> index 84d68b8cfccc86fd87a6a0fd2b70af12e51eb8a4..6e0a8369eee915fab55af24d450a6c40e08def38 100644
>>> --- a/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.yaml
>>> +++ b/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.yaml
>>> @@ -55,6 +55,7 @@ properties:
>>>           - const: amlogic,meson-gx-dw-hdmi
>>>       - enum:
>>>           - amlogic,meson-g12a-dw-hdmi # G12A (S905X2, S905Y2, S905D2)
>>> +          - amlogic,meson-s4-dw-hdmi # S4 (S905Y4)
>>> 
>>>   reg:
>>>     maxItems: 1
>>> 
>>> --
>>> 2.43.0
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> linux-amlogic mailing list
>>> linux-amlogic@...ts.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-amlogic
>> _______________________________________________
>> linux-amlogic mailing list
>> linux-amlogic@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-amlogic
> 

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