Re: [PATCH v2 11/24] arm64: dts: qcom: sm8450: 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 PDC register window to 0x10000 bytes in the device tree triggers an unconditional boot warning from the qcom-pdc driver and fails to actually reduce the memory mapping size at runtime.
--

commit 146bc09492c2a09bab10da04c80ce9d1782cd06d
Author: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>

arm64: dts: qcom: sm8450: Reduce OS PDC DRV span to 0x10000

The OS PDC DRV register window on sm8450 spans 0x10000 bytes. This commit
reduces the size of the first reg entry from 0x30000 to 0x10000.

> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> index 03bf30b53f289..1724204852553 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -3728,7 +3728,7 @@ dispcc: clock-controller@af00000 {
>  
>  		pdc: interrupt-controller@b220000 {
>  			compatible = "qcom,sm8450-pdc", "qcom,pdc";
> -			reg = <0 0x0b220000 0 0x30000>, <0 0x174000f0 0 0x64>;
> +			reg = <0 0x0b220000 0 0x10000>, <0 0x174000f0 0 0x64>;

[Severity: Medium]
Will this reduction trigger a boot warning and fail to actually reduce the
memory mapped size at runtime?

Looking at qcom_pdc_probe() in drivers/irqchip/qcom-pdc.c, the driver has a
hardcoded minimum region size of QCOM_PDC_SIZE (0x30000) to work around older
broken device trees:

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);
    ...
}

If the resource size is reduced to 0x10000 in the device tree without removing
or updating this constraint in the driver, the driver will print the
"invalid reg size" warning on boot and continue to ioremap 0x30000 bytes
anyway.

>  			qcom,pdc-ranges = <0 480 12>, <14 494 24>, <40 520 54>,
>  					  <94 609 31>, <125 63 1>, <126 716 12>;
>  			#interrupt-cells = <2>;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260527094333.2311731-1-mukesh.ojha@oss.qualcomm.com?part=11