Re: [PATCH 3/5] bus: mhi: host: pci_generic: Read SUBSYSTEM_VENDOR_ID for VF's to check status

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

On 7/3/2025 8:39 PM, Vivek.Pernamitta@quicinc.com wrote:
> From: Vivek Pernamitta <quic_vpernami@quicinc.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@oss.qualcomm.com>

- Krishna Chaitanya.
> Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.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;
>