Re: [PATCH 2/3] soc: mediatek: cmdq-helper: add legacy GCE ISA support

[Roman Vivchar]

Hi Angelo,

On Tuesday, July 28th, 2026 at 6:08 PM, AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:

> On 7/28/26 11:42, Roman Vivchar via B4 Relay wrote:
> > From: Roman Vivchar <rva333@xxxxxxxxxxxxxx>
> >
> > Some SoCs, such as mt6572, have different WRITE and POLL instruction
> > encoding. Instead of 16-bit offset and 8-bit subsystem ID, old GCEs have
> > 22-bit offset and 2-bit subsystem ID.
> 
> What about poll_addr, mask, write_s, write_s_mask and others?

These don't seem to exist in all 65xx except 6595. TL;DR - old GCEs are
essentially dumb compared to newer ones. They have only basics like MASK (0x2),
WRITE (0x4), POLL (0x8), JUMP (0x10), WFE (0x20) and EOC (0x40). All logical
operations as well as GPR/SPR don't seem to exist.

cmdq_pkt_poll_addr, write_s, write_s_mask are not used by the DRM subsystem.
mask is the same across all GCEs because it takes only u32 mask without
address.

> Not sure that this will actually work reliably (though I'm sure you're not
> creating any regression).

I have tested this change (on top of out-of-tree mt6572 DRM) with some
dd if=/dev/urandom of=/dev/null spam + modetest, as well as igt. Seems to
work without issues...

Best regards,
Roman