Re: [PATCH] arm64: dts: qcom: shikra-evk: Add GPIO expanders

[Komal Bajaj <komal.bajaj@oss.qualcomm.com>]

On 9/24/2026 6:11 PM, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> - [High] dts: I2C GPIO expanders placed under UART node
> - [Medium] dts: I2C addresses mismatch hardware compatible strings
> --
>
> commit 32fcaaddae686bf893114a2f4648aee0e464eb7f
> Author: Komal Bajaj <komal.bajaj@oss.qualcomm.com>
>
> arm64: dts: qcom: shikra-evk: Add GPIO expanders
>
> This commit adds definitions for TCA9538 and TCA9539 GPIO expanders used on
> the shikra-evk board. It maps them at various I2C addresses.
>
>> diff --git a/arch/arm64/boot/dts/qcom/shikra-evk.dtsi b/arch/arm64/boot/dts/qcom/shikra-evk.dtsi
>> index 0115fc9095b3b..04faf09b21ae0 100644
>> --- a/arch/arm64/boot/dts/qcom/shikra-evk.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/shikra-evk.dtsi
>> @@ -29,4 +29,32 @@ tpm@0 {
>>   
>>   &uart0 {
>>   	status = "okay";
>> +
>> +	expander0: pca953x@38 {
> [Severity: High]
> Are these I2C GPIO expanders placed under the correct parent node?
>
> Because they are defined as children of uart0, they will likely fail to probe
> and cause device tree validation errors since UART controllers do not
> instantiate I2C devices. The commit message mentions the I2C3 bus, should
> these be placed under a node like &i2c3 instead?

Thanks for spotting this.
GPIO expander nodes are incorrectly placed under uart0. I will move them 
under the appropriate I2C controller in the next revision.

>
>> +		compatible = "ti,tca9538";
>> +		reg = <0x38>;
> [Severity: Medium]
> Does the ti,tca9538 compatible string match the hardware at I2C address 0x38?
>
> The TCA9538 hardware strictly uses addresses 0x70 through 0x73, while
> address 0x38 typically corresponds to PCA9554A. Using a mismatched compatible
> string might cause failures if chip-specific quirks are needed later.

The compatible string is correct and match the hardware used on board. I 
verified this against the board schematics.
The comment appears to be based on TI datasheet address assumptions, 
which are not applicable to this design.
Thus, no change is needed.

>
>> +		#gpio-cells = <2>;
>> +		gpio-controller;
>> +	};
>> +
> [ ... ]
>> +
>> +	expander2: pca953x@20 {
>> +		compatible = "ti,tca9539";
>> +		reg = <0x20>;
> [Severity: Medium]
> Is ti,tca9539 the correct compatible string for address 0x20?
>
> The TCA9539 hardware strictly uses addresses 0x74 through 0x77, whereas
> address 0x20 usually belongs to TCA9535 or PCA9555. Using the wrong compatible
> string can inaccurately describe the hardware and lead to issues.

Same applies here.

Thanks
Komal

>
>> +		#gpio-cells = <2>;
>> +		gpio-controller;
>> +	};