Re: [PATCH] PCI: dwc: Fix signedness bug in fault injection test code

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Register accesses without ensuring active power state (missing pm_runtime).
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commit 4899a9300a95dd54caf44bf07153849d88f68ae7
Author: Dan Carpenter <error27@gmail.com>

PCI: dwc: Fix signedness bug in fault injection test code

This commit fixes a signedness bug in the fault injection debugfs handler.
It ensures that negative error codes from kstrtou32 are properly handled by
storing the return value in an int instead of a u32.

> diff --git a/drivers/pci/controller/dwc/pcie-designware-debugfs.c b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
> index d0884253be97e..4bfc1748f2d73 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-debugfs.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
[ ... ]
> @@ -327,10 +328,10 @@ static ssize_t err_inj_write(struct file *file, const char __user *buf,
>  			return -EINVAL;
>  		}
>  	} else {
> -		val = kstrtou32(kern_buf, 0, &counter);
> -		if (val) {
> +		ret = kstrtou32(kern_buf, 0, &counter);
> +		if (ret) {
>  			kfree(kern_buf);
> -			return val;
> +			return ret;
>  		}
>  	}

This isn't a regression introduced by this commit, but is it safe to access
the hardware registers immediately after this block without ensuring the
device is in an active power state?

This function handles user writes to debugfs, which can happen at any time.
If the PCIe controller is runtime-suspended, accessing its memory-mapped
registers via dw_pcie_readl_dbi() might cause a bus hang or kernel panic.

Would it make sense to call pm_runtime_get_sync() before interacting with
the hardware registers later in this function?

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Sashiko AI review · https://sashiko.dev/#/patchset/agL-Uwfn26SI4Gb0@stanley.mountain?part=1