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Date: Sat, 15 Aug 2026 09:24:08 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Vidya Sagar <vidyas@nvidia.com>
Cc: bhelgaas@google.com, vsethi@nvidia.com, sdonthineni@nvidia.com,
	kthota@nvidia.com, mmaddireddy@nvidia.com, kumarahul@nvidia.com,
	sagar.tv@gmail.com, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH V3 5/5] PCI: pciehp: Clear stale 14-Bit Tag Requester
 Enable on hot add
Message-ID: <aoAUGPdr9nKj7OZm@wunner.de>
References: <20260814201621.2281245-1-vidyas@nvidia.com>
 <20260814201621.2281245-6-vidyas@nvidia.com>
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In-Reply-To: <20260814201621.2281245-6-vidyas@nvidia.com>

On Sat, Aug 15, 2026 at 01:46:21AM +0530, Vidya Sagar wrote:
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -302,6 +302,14 @@ int pciehp_check_link_status(struct controller *ctrl)
>  	if (ctrl->inband_presence_disabled)
>  		pcie_wait_for_presence(pdev);
>  
> +	/*
> +	 * The link is up, but a newly inserted card may have trained it in a
> +	 * different mode than the card that was removed left it in.  Drop a
> +	 * now stale 14-Bit Tag Requester Enable on the Port before the first
> +	 * config read below, which the Port issues as the requester.
> +	 */
> +	pci_bridge_refresh_14bit_tag(pdev);
> +
>  	found = pci_bus_check_dev(ctrl->pcie->port->subordinate,
>  					PCI_DEVFN(0, 0));

pciehp_check_link_status() should only do what its name implies,
i.e. return whether the link is up.  It should not have side effects
like mutating register state.

I instead suggest clearing 10-Bit and 14-Bit enablement in
pciehp_unconfigure_device(), i.e. on removal.

Thanks,

Lukas