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

[Roman Vivchar]

On Tuesday, July 28th, 2026 at 6:52 PM, AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:

> On 7/28/26 17:47, Roman Vivchar wrote:
> > 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
> 
> Alright then - look, I'd really want to pick this one up, but it's a bit late
> in the cycle and I don't really have much time left for testing.
> 
> I'm sure that this is fine, but please understand me - I can't take this now,
> also because I'm going on holiday very soon and can't be here to take care of
> sudden breakages.
> 
> I wonder if you could resend it in the next cycle, preferrably at the beginning?

Sure, no problem :)

> 
> Meanwhile, I'll get this series on the Collabora trees so that it gets cycled by
> the CI a bit (though, it's not enough, because that needs to be tested manually).

I don't know if this one can be tested with the upstream tree (if you mean
legacy ISA)... Most likely you need some 65xx (besides 6577 and 6595) or
81xx, but I don't know about 81xx GCE. There's some effort for 6582 and
6589, but none has DRM (and so GCE) so far.

Best regards,
Roman