Re: [PATCH v2 06/24] arm64: dts: qcom: sc8180x: Reduce OS PDC DRV span to 0x10000

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Reducing the `reg` property size to 0x10000 in the device tree triggers a hardcoded override and a boot warning in the PDC driver, failing to actually reduce the mapped memory size.
--

commit 801af88b2159c6cae68a0fa2faaac6413c1a3461
Author: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>

arm64: dts: qcom: sc8180x: Reduce OS PDC DRV span to 0x10000

The OS PDC DRV register window on sc8180x spans 0x10000 bytes. Reduce
the size of the first reg entry from 0x30000 to 0x10000.

> diff --git a/arch/arm64/boot/dts/qcom/sc8180x.dtsi b/arch/arm64/boot/dts/qcom/sc8180x.dtsi
> index f45deb188c6c0..bafdbcd329e9a 100644
> --- a/arch/arm64/boot/dts/qcom/sc8180x.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc8180x.dtsi
> @@ -3554,7 +3554,7 @@ dispcc: clock-controller@af00000 {
>  
>  		pdc: interrupt-controller@b220000 {
>  			compatible = "qcom,sc8180x-pdc", "qcom,pdc";
> -			reg = <0 0x0b220000 0 0x30000>;
> +			reg = <0 0x0b220000 0 0x10000>;

[Severity: Medium]
Will this change actually reduce the mapped memory size, or will it just
trigger a warning on boot?

Looking at the qcom-pdc driver in drivers/irqchip/qcom-pdc.c, there is a
hardcoded minimum size check for the reg property:

drivers/irqchip/qcom-pdc.c:qcom_pdc_probe() {
	...
	res_size = max_t(resource_size_t, resource_size(&res), QCOM_PDC_SIZE);
	if (res_size > resource_size(&res))
		pr_warn("%pOF: invalid reg size, please fix DT\n", node);

	...
	pdc_base = ioremap(res.start, res_size);
	...
}

Since QCOM_PDC_SIZE is 0x30000, passing a size of 0x10000 here will cause the
driver to expand the mapped memory back to 0x30000 and emit a warning on every
boot.

Does the driver logic need to be updated alongside this device tree change to
prevent this warning and successfully reduce the memory footprint?

>  			qcom,pdc-ranges = <0 480 94>, <94 609 31>;
>  			#interrupt-cells = <2>;
>  			interrupt-parent = <&intc>;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260527094333.2311731-1-mukesh.ojha@oss.qualcomm.com?part=6