linux-kernel - Re: [PATCH V2] PCI/TPH: Skip Root Port completer check for RC

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Message-ID: <ea5d11ef-d201-4062-908b-0da69d2bf955@intel.com>
Date: Wed, 17 Dec 2025 17:57:11 +0530
From: George Abraham P <george.abraham.p@...el.com>
To: <bhelgaas@...gle.com>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<giovanni.cabiddu@...el.com>
Subject: Re: [PATCH V2] PCI/TPH: Skip Root Port completer check for RC_END
 devices

Hi Bjorn,

On 16-Oct-25 1:50 PM, George Abraham P wrote:
> Root Complex Integrated Endpoint devices (PCI_EXP_TYPE_RC_END) are
> directly integrated into the root complex and do not have an
> associated Root Port in the traditional PCIe hierarchy. The current
> TPH implementation incorrectly attempts to find and check a Root Port's
> TPH completer capability for these devices.
> 
> Add a check to skip Root Port completer type verification for RC_END
> devices, allowing them to use their full TPH requester capability
> without being limited by a non-existent Root Port's completer support.
> 
> For RC_END devices, the root complex itself acts as the TPH completer,
> and this relationship is handled differently than the standard
> endpoint-to-Root-Port model.
> 
> Fixes: f69767a1ada3 ("PCI: Add TLP Processing Hints (TPH) support")
> Signed-off-by: George Abraham P <george.abraham.p@...el.com>
> ---
> v1->v2:
>   - Added "Fixes:" tag to link the commit hash that introduced the code
> 
>  drivers/pci/tph.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
> index cc64f93709a4..c61456d24f61 100644
> --- a/drivers/pci/tph.c
> +++ b/drivers/pci/tph.c
> @@ -397,10 +397,13 @@ int pcie_enable_tph(struct pci_dev *pdev, int mode)
>  	else
>  		pdev->tph_req_type = PCI_TPH_REQ_TPH_ONLY;
>  
> -	rp_req_type = get_rp_completer_type(pdev);
> +	/* Check if the device is behind a Root Port */
> +	if (pci_pcie_type(pdev) != PCI_EXP_TYPE_RC_END) {
> +		rp_req_type = get_rp_completer_type(pdev);
>  
> -	/* Final req_type is the smallest value of two */
> -	pdev->tph_req_type = min(pdev->tph_req_type, rp_req_type);
> +		/* Final req_type is the smallest value of two */
> +		pdev->tph_req_type = min(pdev->tph_req_type, rp_req_type);
> +	}
>  
>  	if (pdev->tph_req_type == PCI_TPH_REQ_DISABLE)
>  		return -EINVAL;
> 
> base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787

Kindly let me know if there is anything i can do to take this patch forward.

Thanks,
George