i2c: Detect secondary SMBus controller on AMD AM4 chipsets

The AMD X370 and other AM4 chipsets (A/B/X 3/4/5 parts) and Threadripper equivalents have a secondary SMBus controller at I/O port address 0x0B20.  This bus is used by several manufacturers to control motherboard RGB lighting via embedded controllers.  I have been using this bus in my OpenRGB project to control the Aura RGB on many motherboards and ASRock also uses this bus for their Polychrome RGB controller.

See this kernel bug report: https://bugzilla.kernel.org/show_bug.cgi?id=202587

I am not aware of any CZ-compatible platforms which do not have the second SMBus channel.  All of AMD's AM4- and Threadripper- series chipsets that OpenRGB users have tested appear to have this secondary bus.  I also noticed this secondary bus is present on older AMD platforms including my FM1 home server.

Signed-off-by: Adam Honse <calcprogrammer1@gmail.com>

---
 drivers/i2c/busses/i2c-piix4.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Hi Adam,

On Fri, 10 Apr 2020 15:48:44 -0500, Adam Honse wrote:
> The AMD X370 and other AM4 chipsets (A/B/X 3/4/5 parts) and Threadripper equivalents have a secondary SMBus controller at I/O port address 0x0B20.  This bus is used by several manufacturers to control motherboard RGB lighting via embedded controllers.  I have been using this bus in my OpenRGB project to control the Aura RGB on many motherboards and ASRock also uses this bus for their Polychrome RGB controller.
> 
> See this kernel bug report: https://bugzilla.kernel.org/show_bug.cgi?id=202587
> 
> I am not aware of any CZ-compatible platforms which do not have the second SMBus channel.  All of AMD's AM4- and Threadripper- series chipsets that OpenRGB users have tested appear to have this secondary bus.  I also noticed this secondary bus is present on older AMD platforms including my FM1 home server.

Please wrap the patch description at 75 columns. Note that
./scripts/checkpatch.pl would tell you about that.

Maybe Wolfram can fix if for your this time, if not you'll have to
resubmit.

> 
> Signed-off-by: Adam Honse <calcprogrammer1@gmail.com>
> 
> ---
>  drivers/i2c/busses/i2c-piix4.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
> index 30ded6422e7b..69740a4ff1db 100644
> --- a/drivers/i2c/busses/i2c-piix4.c
> +++ b/drivers/i2c/busses/i2c-piix4.c
> @@ -977,7 +977,8 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  	}
>  
>  	if (dev->vendor == PCI_VENDOR_ID_AMD &&
> -	    dev->device == PCI_DEVICE_ID_AMD_HUDSON2_SMBUS) {
> +	    (dev->device == PCI_DEVICE_ID_AMD_HUDSON2_SMBUS ||
> +	     dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS)) {
>  		retval = piix4_setup_sb800(dev, id, 1);
>  	}
>  

Fine with me.

Reviewed-by: Jean Delvare <jdelvare@suse.de>

Ah, one thing I forgot: subject line should start with "i2c: piix4: "
so that it is clear which driver is affected.

On Fri, Apr 10, 2020 at 03:48:44PM -0500, Adam Honse wrote:
> The AMD X370 and other AM4 chipsets (A/B/X 3/4/5 parts) and Threadripper equivalents have a secondary SMBus controller at I/O port address 0x0B20.  This bus is used by several manufacturers to control motherboard RGB lighting via embedded controllers.  I have been using this bus in my OpenRGB project to control the Aura RGB on many motherboards and ASRock also uses this bus for their Polychrome RGB controller.
> 
> See this kernel bug report: https://bugzilla.kernel.org/show_bug.cgi?id=202587
> 
> I am not aware of any CZ-compatible platforms which do not have the second SMBus channel.  All of AMD's AM4- and Threadripper- series chipsets that OpenRGB users have tested appear to have this secondary bus.  I also noticed this secondary bus is present on older AMD platforms including my FM1 home server.
> 
> Signed-off-by: Adam Honse <calcprogrammer1@gmail.com>
> 

Reformatted the patch description, added Sebastians tags and applied to
for-next, thanks!