Re: [PATCH v1] Support Intel Xe GPU dirver Porting on RISC-V Architecture

[Simon Richter <Simon.Richter@hogyros.de>]

Hi,

On 7/15/25 15:18, zhangzhijie wrote:

>      inb/outb speccial wire not support on other ARCH.
> Should detect whether arch platform support or not.

Are you sure these aren't memory mapped?

E.g. POWER defines a global variable with the base of the PCI mapped 
area, uses that in the inb/outb macros to generate loads/stores, and 
configures the root complex to forward accesses to the first 256 bytes 
as I/O TLPs.

Bridges have special handling for VGA addresses, so they can be 
forwarded even if no I/O ranges exist.

Also, this code is probably not used in the Xe driver -- the only VGA 
accesses performed here are a palette read and subsequent write of the 
same value, which is needed for some reason after turning off a voltage 
regulator[1]. If the legacy ports in your system are mapped properly, 
then you might not even run into that problem.

    Simon

[1] https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/1824