[PATCH v2 1/5] drm/i915/gsc: fixes and updates for GSC memory allocation

[Teres Alexis, Alan Previn]

On Mon, 2023-06-05 at 19:23 -0700, Ceraolo Spurio, Daniele wrote:
> A few fixes/updates are required around the GSC memory allocation and it
> is easier to do them all at the same time. The changes are as follows:
> 
> 1 - Switch the memory allocation to stolen memory. We need to avoid
> accesses from GSC FW to normal memory after the suspend function has
> completed and to do so we can either switch to using stolen or make sure
> the GSC is gone to sleep before the end of the suspend function. Given
> that the GSC waits for a bit before going idle even if there are no
> pending operations, it is easier and quicker to just use stolen memory.
> 
> 2 - Reduce the GSC allocation size to 4MBs, which is the POR requirement.
> The 8MBs were needed only for early FW and I had misunderstood that as
> being the expected POR size when I sent the original patch.
> 
> 3 - Perma-map the GSC allocation. This isn't required immediately, but it
> will be needed later to be able to quickly extract the GSC logs, which are
> inside the allocation. Since the mapping code needs to be rewritten due to
> switching to stolen, it makes sense to do the switch immediately to avoid
> having to change it again later.
> 
> Note that the explicit setting of CACHE_NONE for Wa_22016122933 has been
> dropped because that's the default setting for stolen memory on !LLC
> platforms.
> 
> v2: only memset the memory we're not overwriting (Alan)
> 
LGTM so ..
Reviewed-by: Alan Previn <alan.previn.teres.alexis at intel.com>