drm/i915/uc: Improve tracking of uC init status

To be able to setup GuC submission functions during engine init we need
to commit to using GuC as soon as possible.
Currently, the only thing that can stop us from using the
microcontrollers once we've fetched the blobs is a fundamental
error (e.g. OOM); given that if we hit such an error we can't really
fall-back to anything, we can "officialize" the FW fetching completion
as the moment at which we're committing to using GuC.

To better differentiate this case, the uses_guc check, which indicates
that GuC is supported and was selected in modparam, is renamed to
wants_guc and a new uses_guc is introduced to represent the case were
we're committed to using the GuC. Note that uses_guc does still not imply
that the blob is actually loaded on the HW (is_running is the check for
that). Also, since we need to have attempted the fetch for the result
of uses_guc to be meaningful, we need to make sure we've moved away
from INTEL_UC_FIRMWARE_SELECTED.

All the GuC changes have been mirrored on the HuC for coherency.

v2: split fetch return changes and new macros to their own patches,
    support HuC only if GuC is wanted, improve "used" state
    description (Michal)

v3: s/wants_huc/uses_huc in uc_init_wopcm

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Fernando Pacheco <fernando.pacheco@intel.com> #v1
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200218223327.11058-6-daniele.ceraolospurio@intel.com

1 files changed, 23 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.h b/drivers/gpu/drm/i915/gt/uc/intel_uc.h
index 2ce993ceb60a..a41aaf353f88 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.h
@@ -40,6 +40,27 @@ void intel_uc_runtime_suspend(struct intel_uc *uc);
 int intel_uc_resume(struct intel_uc *uc);
 int intel_uc_runtime_resume(struct intel_uc *uc);
 
+/*
+ * We need to know as early as possible if we're going to use GuC or not to
+ * take the correct setup paths. Additionally, once we've started loading the
+ * GuC, it is unsafe to keep executing without it because some parts of the HW,
+ * a subset of which is not cleaned on GT reset, will start expecting the GuC FW
+ * to be running.
+ * To solve both these requirements, we commit to using the microcontrollers if
+ * the relevant modparam is set and the blobs are found on the system. At this
+ * stage, the only thing that can stop us from attempting to load the blobs on
+ * the HW and use them is a fundamental issue (e.g. no memory for our
+ * structures); if we hit such a problem during driver load we're broken even
+ * without GuC, so there is no point in trying to fall back.
+ *
+ * Given the above, we can be in one of 4 states, with the last one implying
+ * we're committed to using the microcontroller:
+ * - Not supported: not available in HW and/or firmware not defined.
+ * - Supported: available in HW and firmware defined.
+ * - Wanted: supported + enabled in modparam.
+ * - In use: wanted + firmware found on the system and successfully fetched.
+ */
+
 #define __uc_state_checker(x, state, required) \
 static inline bool intel_uc_##state##_##x(struct intel_uc *uc) \
 { \
@@ -48,7 +69,8 @@ static inline bool intel_uc_##state##_##x(struct intel_uc *uc) \
 
 #define uc_state_checkers(x) \
 __uc_state_checker(x, supports, supported) \
-__uc_state_checker(x, uses, enabled)
+__uc_state_checker(x, wants, wanted) \
+__uc_state_checker(x, uses, used)
 
 uc_state_checkers(guc);
 uc_state_checkers(huc);