RE: [PATCH 00/10] drm/i915/spi: spi access for discrete graphics

Usyskin, Alexander
2023-09-27T14:12:11Z

>
> > > This sounds like there's some sort of MFD rather than or as well as a flash
> > > chip, or possibly multiple SPI devices?
>
> > Yes, the driver doesn't talk to SPI controller directly it goes via
> > another layer, so all SPI standard HW is not accessible, but we wish
> > to expose the MTD interface.
>
> Perhaps if you described clearly and directly the actual system you are
> trying to model then it would be easier to tell how it fits into the
> kernel? What is the actual interface here - how does the host interact
> with the flash?
>
> Also to repeat: please fix your mail client to word wrap within
> paragraphs at something substantially less than 80 columns. Doing this
> makes your messages much easier to read and reply to.

Sorry for that, I'm fairly new in SPI and MTD subsystems.
Will try to describe as best as I could.

There is a Discreet Graphic device with embedded SPI (controller & flash).
The embedded SPI is not visible to OS.
There is another HW in the chip that gates access to the controller and
exposes registers for:
region select; read and write (4 and 8 bytes); erase (4K); error register;

There are two main usages - user-space manufacturing and repair
application that requires unrestricted read/write/erase over flash chip
and kernel module that requires read access to one of flash regions
for configuration.

--
Alexander (Sasha) Usyskin

CSE FW Dev - Host SW
Intel Israel (74) Limited