drm/xe/gsc: do not flush the GSC worker from the reset path

drm/xe/gsc: do not flush the GSC worker from the reset path

commit 03552d8ac0afcc080c339faa0b726e2c0e9361cb upstream.

The workqueue used for the reset worker is marked as WQ_MEM_RECLAIM,
while the GSC one isn't (and can't be as we need to do memory
allocations in the gsc worker). Therefore, we can't flush the latter
from the former.

The reason why we had such a flush was to avoid interrupting either
the GSC FW load or in progress GSC proxy operations. GSC proxy
operations fall into 2 categories:

1) GSC proxy init: this only happens once immediately after GSC FW load
   and does not support being interrupted. The only way to recover from
   an interruption of the proxy init is to do an FLR and re-load the GSC.

2) GSC proxy request: this can happen in response to a request that
   the driver sends to the GSC. If this is interrupted, the GSC FW will
   timeout and the driver request will be failed, but overall the GSC
   will keep working fine.

Flushing the work allowed us to avoid interruption in both cases (unless
the hang came from the GSC engine itself, in which case we're toast
anyway). However, a failure on a proxy request is tolerable if we're in
a scenario where we're triggering a GT reset (i.e., something is already
gone pretty wrong), so what we really need to avoid is interrupting
the init flow, which we can do by polling on the register that reports
when the proxy init is complete (as that ensure us that all the load and
init operations have been completed).

Note that during suspend we still want to do a flush of the worker to
make sure it completes any operations involving the HW before the power
is cut.

v2: fix spelling in commit msg, rename waiter function (Julia)

Fixes: dd0e89e5edc2 ("drm/xe/gsc: GSC FW load")
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4830
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: <stable@vger.kernel.org> # v6.8+
Reviewed-by: Julia Filipchuk <julia.filipchuk@intel.com>
Link: https://lore.kernel.org/r/20250502155104.2201469-1-daniele.ceraolospurio@intel.com
(cherry picked from commit 12370bfcc4f0bdf70279ec5b570eb298963422b5)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>