Re: [PATCH v4 8/8] i2c: designware: Add doorbell support for Skyrim

[Jarkko Nikula]

On 3/10/23 23:19, Mario Limonciello wrote:
> Skyrim and later platform don't use the platform feature mailbox for
> communication for I2C arbitration, they rely upon ringing a doorbell.
>
> Detect the platform by the device ID of the root port and choose the
> appropriate method.
>
> Link: https://lore.kernel.org/linux-i2c/20220916131854.687371-3-jsd@xxxxxxxxxxxx/
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> v3->v4:
>   * Adjust to use PCI device ID and function pointers instead
> v2->v3:
>   * Use CPU ID rather than ACPI ID, this will be pushed to a later patch
> v1->v2:
>   * New patch
> ---
>   drivers/i2c/busses/i2c-designware-amdpsp.c | 40 ++++++++++++++++------
>   1 file changed, 30 insertions(+), 10 deletions(-)
...

> @@ -276,6 +289,13 @@ int i2c_dw_amdpsp_probe_lock_support(struct dw_i2c_dev *dev)
>   	if (psp_i2c_dev)
>   		return -EEXIST;
>   
> +	/* Cezanne uses platform mailbox, Skyrim and later use doorbell */
> +	rdev = pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(0, 0));
> +	if (rdev->device == 0x1630)
> +		_psp_send_i2c_req = psp_send_i2c_req_cezanne;
> +	else
> +		_psp_send_i2c_req = psp_send_i2c_req_skyrim;
> +

Is there any possibility pci_get_domain_bus_and_slot() returns NULL? Or 
is 00:00.0 always present?