linux-kernel - Re: [PATCH 2/4] dt-bindings: display: amlogic, meson-dw-hdmi: Add optional HDMI 5V regulator

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Message-ID: <9b69d42b-ffc5-32cf-1509-ec8e74fc3825@baylibre.com>
Date:   Tue, 24 Oct 2017 10:09:15 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Rob Herring <robh@...nel.org>
Cc:     airlied@...ux.ie, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] dt-bindings: display: amlogic, meson-dw-hdmi: Add
 optional HDMI 5V regulator

On 24/10/2017 00:46, Rob Herring wrote:
> On Tue, Oct 17, 2017 at 10:07:42AM +0200, Neil Armstrong wrote:
>> On reference boards and derivatives, the HDMI Logic is powered by an external
>> 5V regulator.
>> This regulator was set by the Vendor U-Boot, add optional support for it.
>>
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>> ---
>>  Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.txt | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.txt b/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.txt
>> index 7f040ed..bf4a180 100644
>> --- a/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.txt
>> +++ b/Documentation/devicetree/bindings/display/amlogic,meson-dw-hdmi.txt
>> @@ -48,6 +48,10 @@ Required properties:
>>    Documentation/devicetree/bindings/reset/reset.txt,
>>    the reset-names should be "hdmitx_apb", "hdmitx", "hdmitx_phy"
>>  
>> +Optional properties:
>> +- hdmi-supply: Optional phandle to an external 5V regulator to power the HDMI
>> +  logic, as described in the file ../regulator/regulator.txt
> 
> 5V into a modern SoC sounds strange. Is this really for the chip or for 
> 5V to the connector? The latter should be in the connector node.
> 
> Rob
> 

Hi Rob,

The chip does not get the 5V but multiple derived voltages, but depends on the 5V regulator to
enable this power supply for the connector and to the hdmi io bank.

So in my opinion it's not related to the connector but to the HDMI logic.

Neil