drm/i915/uapi/pxp: Add a GET_PARAM for PXP

Because of the additional firmware, component-driver and
initialization depedencies required on MTL platform before a
PXP context can be created, UMD calling for PXP creation as a
way to get-caps can take a long time. An actual real world
customer stack has seen this happen in the 4-to-8 second range
after the kernel starts (which sees MESA's init appear in the
middle of this range as the compositor comes up). To avoid
unncessary delays experienced by the UMD for get-caps purposes,
add a GET_PARAM for I915_PARAM_PXP_SUPPORT.

However, some failures can still occur after all the depedencies
are met (such as firmware init flow failure, bios configurations
or SOC fusing not allowing PXP enablement). Those scenarios will
only be known to user space when it attempts creating a PXP context
and is documented in the GEM UAPI headers.

While making this change, create a helper that is common to both
GET_PARAM caller and intel_pxp_start since the latter does
similar checks.
Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230511231738.1077674-7-alan.previn.teres.alexis@intel.com

drivers/gpu/drm/i915/i915_getparam.c

@@ -5,6 +5,8 @@
 #include "gem/i915_gem_mman.h"
 #include "gt/intel_engine_user.h"
 
+#include "pxp/intel_pxp.h"
+
 #include "i915_cmd_parser.h"
 #include "i915_drv.h"
 #include "i915_getparam.h"
@@ -102,6 +104,11 @@ int i915_getparam_ioctl(struct drm_device *dev, void *data,
 		if (value < 0)
 			return value;
 		break;
+	case I915_PARAM_PXP_STATUS:
+		value = intel_pxp_get_readiness_status(i915->pxp);
+		if (value < 0)
+			return value;
+		break;
 	case I915_PARAM_MMAP_GTT_VERSION:
 		/* Though we've started our numbering from 1, and so class all
 		 * earlier versions as 0, in effect their value is undefined as

drivers/gpu/drm/i915/pxp/intel_pxp.c

@@ -358,23 +358,38 @@ void intel_pxp_end(struct intel_pxp *pxp)
 }
 
 /*
- * the arb session is restarted from the irq work when we receive the
- * termination completion interrupt
+ * this helper is used by both intel_pxp_start and by
+ * the GET_PARAM IOCTL that user space calls. Thus, the
+ * return values here should match the UAPI spec.
  */
-int intel_pxp_start(struct intel_pxp *pxp)
+int intel_pxp_get_readiness_status(struct intel_pxp *pxp)
 {
-	int ret = 0;
-
 	if (!intel_pxp_is_enabled(pxp))
 		return -ENODEV;
 
 	if (HAS_ENGINE(pxp->ctrl_gt, GSC0)) {
 		if (wait_for(intel_pxp_gsccs_is_ready_for_sessions(pxp), 250))
-			return -ENXIO;
+			return 2;
 	} else {
 		if (wait_for(pxp_component_bound(pxp), 250))
-			return -ENXIO;
+			return 2;
 	}
+	return 1;
+}
+
+/*
+ * the arb session is restarted from the irq work when we receive the
+ * termination completion interrupt
+ */
+int intel_pxp_start(struct intel_pxp *pxp)
+{
+	int ret = 0;
+
+	ret = intel_pxp_get_readiness_status(pxp);
+	if (ret < 0)
+		return ret;
+	else if (ret > 1)
+		return -EIO; /* per UAPI spec, user may retry later */
 
 	mutex_lock(&pxp->arb_mutex);
 

drivers/gpu/drm/i915/pxp/intel_pxp.h

@@ -26,6 +26,7 @@ void intel_pxp_fini_hw(struct intel_pxp *pxp);
 void intel_pxp_mark_termination_in_progress(struct intel_pxp *pxp);
 void intel_pxp_tee_end_arb_fw_session(struct intel_pxp *pxp, u32 arb_session_id);
 
+int intel_pxp_get_readiness_status(struct intel_pxp *pxp);
 int intel_pxp_start(struct intel_pxp *pxp);
 void intel_pxp_end(struct intel_pxp *pxp);
 

include/uapi/drm/i915_drm.h

@@ -771,6 +771,25 @@ typedef struct drm_i915_irq_wait {
  */
 #define I915_PARAM_OA_TIMESTAMP_FREQUENCY 57
 
+/*
+ * Query the status of PXP support in i915.
+ *
+ * The query can fail in the following scenarios with the listed error codes:
+ *     -ENODEV = PXP support is not available on the GPU device or in the
+ *               kernel due to missing component drivers or kernel configs.
+ *
+ * If the IOCTL is successful, the returned parameter will be set to one of
+ * the following values:
+ *     1 = PXP feature is supported and is ready for use.
+ *     2 = PXP feature is supported but should be ready soon (pending
+ *         initialization of non-i915 system dependencies).
+ *
+ * NOTE: When param is supported (positive return values), user space should
+ *       still refer to the GEM PXP context-creation UAPI header specs to be
+ *       aware of possible failure due to system state machine at the time.
+ */
+#define I915_PARAM_PXP_STATUS		 58
+
 /* Must be kept compact -- no holes and well documented */
 
 /**