drm/xe: Make it possible to read instance0 MCR registers after xe_gt_mcr_init_early

After mcr_init_early, we need to be able to do VRAM and CCS probing
without hwconfig probe. Fortunately the relevant registers are all
instance 0, which fortunately means no dependencies on further initialization
is required.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250619104858.418440-17-dev@lankhorst.se
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

diff --git a/drivers/gpu/drm/xe/xe_gt_mcr.c b/drivers/gpu/drm/xe/xe_gt_mcr.c
index d4d9730f0d2c75581ad518beb648035ba543c526..64a2f0d6aaf95f492a7867e42360f580024fb37d 100644 (file)
--- a/drivers/gpu/drm/xe/xe_gt_mcr.c
+++ b/drivers/gpu/drm/xe/xe_gt_mcr.c
@@ -420,12 +420,6 @@ static void init_steering_sqidi_psmi(struct xe_gt *gt)
        gt->steering[SQIDI_PSMI].instance_target = select & 0x1;
 }
 
-static void init_steering_inst0(struct xe_gt *gt)
-{
-       gt->steering[INSTANCE0].group_target = 0;       /* unused */
-       gt->steering[INSTANCE0].instance_target = 0;    /* unused */
-}
-
 static const struct {
        const char *name;
        void (*init)(struct xe_gt *gt);
@@ -436,7 +430,7 @@ static const struct {
        [DSS] =         { "DSS",        init_steering_dss },
        [OADDRM] =      { "OADDRM / GPMXMT", init_steering_oaddrm },
        [SQIDI_PSMI] =  { "SQIDI_PSMI", init_steering_sqidi_psmi },
-       [INSTANCE0] =   { "INSTANCE 0", init_steering_inst0 },
+       [INSTANCE0] =   { "INSTANCE 0", NULL },
        [IMPLICIT_STEERING] = { "IMPLICIT", NULL },
 };
 
@@ -446,25 +440,17 @@ static const struct {
  *
  * Perform early software only initialization of the MCR lock to allow
  * the synchronization on accessing the STEER_SEMAPHORE register and
- * use the xe_gt_mcr_multicast_write() function.
+ * use the xe_gt_mcr_multicast_write() function, plus the minimum
+ * safe MCR registers required for VRAM/CCS probing.
  */
 void xe_gt_mcr_init_early(struct xe_gt *gt)
 {
+       struct xe_device *xe = gt_to_xe(gt);
+
        BUILD_BUG_ON(IMPLICIT_STEERING + 1 != NUM_STEERING_TYPES);
        BUILD_BUG_ON(ARRAY_SIZE(xe_steering_types) != NUM_STEERING_TYPES);
 
        spin_lock_init(&gt->mcr_lock);
-}
-
-/**
- * xe_gt_mcr_init - Normal initialization of the MCR support
- * @gt: GT structure
- *
- * Perform normal initialization of the MCR for all usages.
- */
-void xe_gt_mcr_init(struct xe_gt *gt)
-{
-       struct xe_device *xe = gt_to_xe(gt);
 
        if (IS_SRIOV_VF(xe))
                return;
@@ -505,10 +491,27 @@ void xe_gt_mcr_init(struct xe_gt *gt)
                }
        }
 
+       /* Mark instance 0 as initialized, we need this early for VRAM and CCS probe. */
+       gt->steering[INSTANCE0].initialized = true;
+}
+
+/**
+ * xe_gt_mcr_init - Normal initialization of the MCR support
+ * @gt: GT structure
+ *
+ * Perform normal initialization of the MCR for all usages.
+ */
+void xe_gt_mcr_init(struct xe_gt *gt)
+{
+       if (IS_SRIOV_VF(gt_to_xe(gt)))
+               return;
+
        /* Select non-terminated steering target for each type */
-       for (int i = 0; i < NUM_STEERING_TYPES; i++)
+       for (int i = 0; i < NUM_STEERING_TYPES; i++) {
+               gt->steering[i].initialized = true;
                if (gt->steering[i].ranges && xe_steering_types[i].init)
                        xe_steering_types[i].init(gt);
+       }
 }
 
 /**
@@ -570,6 +573,10 @@ bool xe_gt_mcr_get_nonterminated_steering(struct xe_gt *gt,
 
                for (int i = 0; gt->steering[type].ranges[i].end > 0; i++) {
                        if (xe_mmio_in_range(&gt->mmio, &gt->steering[type].ranges[i], reg)) {
+                               drm_WARN(&gt_to_xe(gt)->drm, !gt->steering[type].initialized,
+                                        "Uninitialized usage of MCR register %s/%#x\n",
+                                        xe_steering_types[type].name, reg.addr);
+
                                *group = gt->steering[type].group_target;
                                *instance = gt->steering[type].instance_target;
                                return true;

diff --git a/drivers/gpu/drm/xe/xe_gt_types.h b/drivers/gpu/drm/xe/xe_gt_types.h
index 7def0959da35d86f516eb8ae403568124ab1477f..96344c604726048721ceac03e4057dd7f886a1d2 100644 (file)
--- a/drivers/gpu/drm/xe/xe_gt_types.h
+++ b/drivers/gpu/drm/xe/xe_gt_types.h
@@ -377,6 +377,8 @@ struct xe_gt {
                u16 group_target;
                /** @steering.instance_target: instance to steer accesses to */
                u16 instance_target;
+               /** @steering.initialized: Whether this steering range is initialized */
+               bool initialized;
        } steering[NUM_STEERING_TYPES];
 
        /**