drm/xe: Add stepping support for GMD_ID platforms

For platforms with GMD_ID registers, the IP stepping should be
determined from the 'revid' field of those registers rather than from
the PCI revid.

The hardware teams have indicated that they plan to keep the revid =>
stepping mapping consistent across all GMD_ID platforms, with major
steppings (A0, B0, C0, etc.) having revids that are multiples of 4, and
minor steppings (A1, A2, A3, etc.) taking the intermediate values.  For
now we'll trust that hardware follows through on this plan; if they have
to change direction in the future (e.g., they wind up needing something
like an "A4" that doesn't fit this scheme), we can add a GMD_ID-based
lookup table when the time comes.

v2:
 - Set xe->info.platform before finding stepping; the pre-GMD_ID code
   relies on this value to pick a lookup table.
v3:
 - Also set xe->info.subplatform before picking the stepping for
   pre-GMD_ID lookup.

Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://lore.kernel.org/r/20230524185952.666158-1-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

1 files changed, 44 insertions, 1 deletions

diff --git a/drivers/gpu/drm/xe/xe_step.c b/drivers/gpu/drm/xe/xe_step.c
index a443d9bd7bbb..1baf79ba02ad 100644
--- a/drivers/gpu/drm/xe/xe_step.c
+++ b/drivers/gpu/drm/xe/xe_step.c
@@ -107,7 +107,14 @@ static const int pvc_basedie_subids[] = {
 
 __diag_pop();
 
-struct xe_step_info xe_step_get(struct xe_device *xe)
+/**
+ * xe_step_pre_gmdid_get - Determine IP steppings from PCI revid
+ * @xe: Xe device
+ *
+ * Convert the PCI revid into proper IP steppings.  This should only be
+ * used on platforms that do not have GMD_ID support.
+ */
+struct xe_step_info xe_step_pre_gmdid_get(struct xe_device *xe)
 {
 	const struct xe_step_info *revids = NULL;
 	struct xe_step_info step = {};
@@ -198,6 +205,42 @@ struct xe_step_info xe_step_get(struct xe_device *xe)
 	return step;
 }
 
+/**
+ * xe_step_gmdid_get - Determine IP steppings from GMD_ID revid fields
+ * @xe: Xe device
+ * @graphics_gmdid_revid: value of graphics GMD_ID register's revid field
+ * @media_gmdid_revid: value of media GMD_ID register's revid field
+ *
+ * Convert the revid fields of the GMD_ID registers into proper IP steppings.
+ *
+ * GMD_ID revid values are currently expected to have consistent meanings on
+ * all platforms:  major steppings (A0, B0, etc.) are 4 apart, with minor
+ * steppings (A1, A2, etc.) taking the values in between.
+ */
+struct xe_step_info xe_step_gmdid_get(struct xe_device *xe,
+				      u32 graphics_gmdid_revid,
+				      u32 media_gmdid_revid)
+{
+	struct xe_step_info step = {
+		.graphics = STEP_A0 + graphics_gmdid_revid,
+		.media = STEP_A0 + media_gmdid_revid,
+	};
+
+	if (step.graphics >= STEP_FUTURE) {
+		step.graphics = STEP_FUTURE;
+		drm_dbg(&xe->drm, "Graphics GMD_ID revid value %d treated as future stepping\n",
+			graphics_gmdid_revid);
+	}
+
+	if (step.media >= STEP_FUTURE) {
+		step.media = STEP_FUTURE;
+		drm_dbg(&xe->drm, "Media GMD_ID revid value %d treated as future stepping\n",
+			graphics_gmdid_revid);
+	}
+
+	return step;
+}
+
 #define STEP_NAME_CASE(name)	\
 	case STEP_##name:	\
 		return #name;