Re: [PATCH v20 11/16] PCI/TPH: Add pci_tph_dsm_supported() helper to detect device TPH ST _DSM

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Medium] The newly added `pcie_tph_dsm_supported()` helper incorrectly evaluates the ACPI _DSM on the Host Bridge instead of the Root Port.
- [Medium] The newly added `pcie_tph_dsm_supported()` helper does not support Root Complex Integrated Endpoints (RCiEPs).
--

--- Patch [11]: [PATCH v20 11/16] PCI/TPH: Add pci_tph_dsm_supported() helper to detect device TPH ST _DSM ---
commit b4b5ff3a7f819f0fbddf034e29a0aa1c625cb893
Author: Chengwen Feng <fengchengwen@huawei.com>

PCI/TPH: Add pci_tph_dsm_supported() helper to detect device TPH ST _DSM

This commit adds a new helper pcie_tph_dsm_supported() to check whether the
root port of a given PCI device exposes the TPH ST ACPI _DSM method. The
logic is guarded by CONFIG_ACPI and returns false if ACPI is disabled.

> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
> index 8194f8b45e3c6..e6a850ab2b037 100644
> --- a/drivers/pci/tph.c
> +++ b/drivers/pci/tph.c
[ ... ]
> +bool pcie_tph_dsm_supported(struct pci_dev *pdev)
> +{
> +#ifdef CONFIG_ACPI
> +	struct pci_dev *rp = pcie_find_root_port(pdev);
> +	acpi_handle handle;
> +
> +	if (!rp || !rp->bus || !rp->bus->bridge)
> +		return false;

[Severity: Medium]
Will this check fail for Root Complex Integrated Endpoints (RCiEPs)?

Since RCiEPs do not have an upstream Root Port, pcie_find_root_port() will
return NULL and this function will return false. Should this include a
fallback to check the associated Root Complex Event Collector (RCEC) for
the _DSM?

> +
> +	handle = ACPI_HANDLE(rp->bus->bridge);

[Severity: Medium]
Is this evaluating the ACPI _DSM on the correct device?

By using rp->bus->bridge, this fetches the ACPI handle of the Host Bridge
(the parent of the Root Port's upstream bus). Since the TPH _DSM is
typically placed on the Root Port itself per the PCI Firmware Specification,
should this use ACPI_HANDLE(&rp->dev) instead to avoid a false negative?

> +	if (!handle)
> +		return false;
[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260714104325.54444-1-fengchengwen@huawei.com?part=11