linux-kernel - Re: [PATCH 3/5] bus: mhi: host: pci_generic: Read SUBSYSTEM_VENDOR

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Message-ID: <7ed53821-c86a-41f0-bb99-ff43ebedd680@oss.qualcomm.com>
Date: Wed, 9 Jul 2025 18:09:48 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Vivek.Pernamitta@...cinc.com, Manivannan Sadhasivam <mani@...nel.org>
Cc: mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vivek Pernamitta <quic_vpernami@...cinc.com>
Subject: Re: [PATCH 3/5] bus: mhi: host: pci_generic: Read SUBSYSTEM_VENDOR_ID
 for VF's to check status



On 7/3/2025 8:39 PM, Vivek.Pernamitta@...cinc.com wrote:
> From: Vivek Pernamitta <quic_vpernami@...cinc.com>
> 
> In SRIOV enabled devices, the VF DEVICE/VENDOR ID register returns FFFFh
> when read (PCIe SRIOV spec-3.4.1.1). Therefore, read the PCIe
> SUBSYSTEM_VENDOR_ID to check if the device is active.
> 
Reviewed-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>

- Krishna Chaitanya.
> Signed-off-by: Vivek Pernamitta <quic_vpernami@...cinc.com>
> ---
>   drivers/bus/mhi/host/pci_generic.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
> index 22de02c26ceb946fb618d962ac8882d2db1be6b4..938f37d306a18b9a47f302df85697f837c225f0d 100644
> --- a/drivers/bus/mhi/host/pci_generic.c
> +++ b/drivers/bus/mhi/host/pci_generic.c
> @@ -1025,8 +1025,10 @@ static bool mhi_pci_is_alive(struct mhi_controller *mhi_cntrl)
>   	struct pci_dev *pdev = to_pci_dev(mhi_cntrl->cntrl_dev);
>   	u16 vendor = 0;
>   
> -	if (pci_read_config_word(pdev, PCI_VENDOR_ID, &vendor))
> -		return false;
> +	if (pdev->is_virtfn)
> +		pci_read_config_word(pdev, PCI_SUBSYSTEM_VENDOR_ID, &vendor);
> +	else
> +		pci_read_config_word(pdev, PCI_VENDOR_ID, &vendor);
>   
>   	if (vendor == (u16) ~0 || vendor == 0)
>   		return false;
>