linux-kernel - Re: [PATCH v6 07/11] arm64: dts: qcom: sa8775p-ride: add anx7625 DSI to DP bridge nodes

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Message-ID: <88b139c4-0a35-4c9e-9993-573fede29b71@quicinc.com>
Date: Tue, 6 May 2025 17:42:50 +0530
From: Ayushi Makhija <quic_amakhija@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <robdclark@...il.com>,
        <sean@...rly.run>, <marijn.suijten@...ainline.org>,
        <andersson@...nel.org>, <robh@...nel.org>, <robh+dt@...nel.org>,
        <krzk+dt@...nel.org>, <konradybcio@...nel.org>, <conor+dt@...nel.org>,
        <andrzej.hajda@...el.com>, <neil.armstrong@...aro.org>,
        <rfoss@...nel.org>, <Laurent.pinchart@...asonboard.com>,
        <jonas@...boo.se>, <jernej.skrabec@...il.com>,
        <quic_abhinavk@...cinc.com>, <quic_rajeevny@...cinc.com>,
        <quic_vproddut@...cinc.com>, <quic_jesszhan@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v6 07/11] arm64: dts: qcom: sa8775p-ride: add anx7625 DSI
 to DP bridge nodes

Hi Dmitry,

On 5/5/2025 3:32 PM, Dmitry Baryshkov wrote:
> On Mon, May 05, 2025 at 03:12:41PM +0530, Ayushi Makhija wrote:
>> Add anx7625 DSI to DP bridge device nodes.
>>
>> Signed-off-by: Ayushi Makhija <quic_amakhija@...cinc.com>
>> Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>> ---
>>  arch/arm64/boot/dts/qcom/sa8775p-ride.dtsi | 183 +++++++++++++++++++++
>>  1 file changed, 183 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/qcom/sa8775p-ride.dtsi b/arch/arm64/boot/dts/qcom/sa8775p-ride.dtsi
>> index 175f8b1e3b2d..de14f3ea8835 100644
>> --- a/arch/arm64/boot/dts/qcom/sa8775p-ride.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/sa8775p-ride.dtsi
>> @@ -28,6 +28,15 @@ chosen {
>>  		stdout-path = "serial0:115200n8";
>>  	};
>>  
>> +	vph_pwr: vph-pwr-regulator {
>> +		compatible = "regulator-fixed";
>> +		regulator-name = "vph_pwr";
>> +		regulator-min-microvolt = <12000000>;
>> +		regulator-max-microvolt = <12000000>;
> 
> 12 V, if my eyes don't deceive me.

Yes, it's 12V. According to the chipset's power grid, the VPH rail is rated at 12 volts.
That's significantly higher than what we typically see on mobile platforms. I guess,
this is due to the SA8775P Ride SX being designed for automotive applications, where higher voltage levels are required.

> 
>> +		regulator-always-on;
>> +		regulator-boot-on;
>> +	};
>> +
> 
> [...]
> 
>> +
>> +			bridge@58 {
>> +				compatible = "analogix,anx7625";
>> +				reg = <0x58>;
>> +				interrupts-extended = <&io_expander 2 IRQ_TYPE_EDGE_FALLING>;
>> +				enable-gpios = <&io_expander 1 GPIO_ACTIVE_HIGH>;
>> +				reset-gpios = <&io_expander 0 GPIO_ACTIVE_HIGH>;
>> +				vdd10-supply = <&vph_pwr>;
>> +				vdd18-supply = <&vph_pwr>;
>> +				vdd33-supply = <&vph_pwr>;
> 
> Here you are saying that 1.0V, 1.8V and 3.3V pins are powered on by 12V
> supply. I wonder how the board doesn't trigger all fire alarms in the
> building.
> 

Let me try to explain the connections from the schematics.

In the SA8775P RIDE SX platform, the ANX bridge supplies are connected from the below sources:

1) AVDD1P8 is sourced from the `VREG_1P8` of the backplane card.
2) AVDD3P0 is sourced from the `VREG_3P0` of the backplane card.
3) AVDD1P0 is sourced from the TPS74801 LDO voltage regulator that has `VREG_1P8` connected to
   VIN & EN lines, and `VREG_3P0` connected to BIAS line.

The `VREG_1P8` is sourced from a buck converter TPS54618CQRTERQ1 that is using 
`VREG_5P0` as VIN and EN_VR1P8_M3P3 as EN signal. 
Where the `EN_VR1P8_M3P3` is an output signal from SAK-TC397XX-256F300S BD micro-controller.

Similarly, the `VREG_1P3` and `VREG_5P0` are sourced from another buck converter LM5143QRWGRQ1
that is using `VREG_12P0` as VIN and `EN_VR5P0_M3P3` as EN signal.
Where the EN_VR5P0_M3P3 is an output from the same micro-controller.

Combining above details, all three ANX bridge supplies are getting enabled by `VREG_12P0` supply,
`EN_VR1P8_M3P3` and `EN_VR5P0_M3P3` signals once the SOC is out of reset.

The `VREG_12P0` is directly sourced from `VBATT_IN`.

Since, there is no SW control for ANX bridge supplies and they are getting enabled
once the SOC is out of reset, I have used vph-pwr-regulator dummy regulator.
I am not sure if it's the right way to handle above scenario. Please let me know if there is other way to do the same.

Thanks,
Ayushi

>> +
>