[Intel-gfx] [PATCH] drm/i915: Don't access non-existent PGTBL_ER register

[Chris Wilson]

Quoting Matt Roper (2021-01-30 00:16:20)
> PGTBL_ER (0x2024) isn't documented in the bspec of any recent (SNB+)
> platform; it seems this register was removed ages ago and we probably
> shouldn't still be trying to clear it at init or read it during error
> state dump.

We do support decoding of PGTBL_ERR from the error state on gen2-gen4,
so that suggests we did have the definition at some point.

I would keep it in the error state and just read it on gen<6.

One day we will get per-platform lists of registers to snapshot for
errors.
-Chris