drm/i915/gen6+: Interpret mailbox error flags

In order to add proper support for the SAGV, we need to be able to know
what the cause of a failure to change the SAGV through the pcode mailbox
was. The reasoning for this is that some very early pre-release Skylake
machines don't actually allow you to control the SAGV on them, and
indicate an invalid mailbox command was sent.

This also might come in handy in the future for debugging.

Changes since v1:
 - Add functions for interpreting gen6 mailbox error codes along with
   gen7+ error codes, and actually interpret those codes properly
 - Renamed patch to reflect new behavior

Signed-off-by: Lyude <cpaul@redhat.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471463761-26796-2-git-send-email-cpaul@redhat.com
[mlankhorst: -ENOSYS -> -ENXIO for checkpatch]

(cherry picked from commit 87660502f1a4d51fb043e89a45d30c9917787c22)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

1 files changed, 70 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 421c5b72464a..2c88c2f50d02 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -7671,8 +7671,53 @@ void intel_init_pm(struct drm_device *dev)
 	}
 }
 
+static inline int gen6_check_mailbox_status(struct drm_i915_private *dev_priv)
+{
+	uint32_t flags =
+		I915_READ_FW(GEN6_PCODE_MAILBOX) & GEN6_PCODE_ERROR_MASK;
+
+	switch (flags) {
+	case GEN6_PCODE_SUCCESS:
+		return 0;
+	case GEN6_PCODE_UNIMPLEMENTED_CMD:
+	case GEN6_PCODE_ILLEGAL_CMD:
+		return -ENXIO;
+	case GEN6_PCODE_MIN_FREQ_TABLE_GT_RATIO_OUT_OF_RANGE:
+		return -EOVERFLOW;
+	case GEN6_PCODE_TIMEOUT:
+		return -ETIMEDOUT;
+	default:
+		MISSING_CASE(flags)
+		return 0;
+	}
+}
+
+static inline int gen7_check_mailbox_status(struct drm_i915_private *dev_priv)
+{
+	uint32_t flags =
+		I915_READ_FW(GEN6_PCODE_MAILBOX) & GEN6_PCODE_ERROR_MASK;
+
+	switch (flags) {
+	case GEN6_PCODE_SUCCESS:
+		return 0;
+	case GEN6_PCODE_ILLEGAL_CMD:
+		return -ENXIO;
+	case GEN7_PCODE_TIMEOUT:
+		return -ETIMEDOUT;
+	case GEN7_PCODE_ILLEGAL_DATA:
+		return -EINVAL;
+	case GEN7_PCODE_MIN_FREQ_TABLE_GT_RATIO_OUT_OF_RANGE:
+		return -EOVERFLOW;
+	default:
+		MISSING_CASE(flags);
+		return 0;
+	}
+}
+
 int sandybridge_pcode_read(struct drm_i915_private *dev_priv, u32 mbox, u32 *val)
 {
+	int status;
+
 	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
 
 	/* GEN6_PCODE_* are outside of the forcewake domain, we can
@@ -7699,12 +7744,25 @@ int sandybridge_pcode_read(struct drm_i915_private *dev_priv, u32 mbox, u32 *val
 	*val = I915_READ_FW(GEN6_PCODE_DATA);
 	I915_WRITE_FW(GEN6_PCODE_DATA, 0);
 
+	if (INTEL_GEN(dev_priv) > 6)
+		status = gen7_check_mailbox_status(dev_priv);
+	else
+		status = gen6_check_mailbox_status(dev_priv);
+
+	if (status) {
+		DRM_DEBUG_DRIVER("warning: pcode (read) mailbox access failed: %d\n",
+				 status);
+		return status;
+	}
+
 	return 0;
 }
 
 int sandybridge_pcode_write(struct drm_i915_private *dev_priv,
-			       u32 mbox, u32 val)
+			    u32 mbox, u32 val)
 {
+	int status;
+
 	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
 
 	/* GEN6_PCODE_* are outside of the forcewake domain, we can
@@ -7729,6 +7787,17 @@ int sandybridge_pcode_write(struct drm_i915_private *dev_priv,
 
 	I915_WRITE_FW(GEN6_PCODE_DATA, 0);
 
+	if (INTEL_GEN(dev_priv) > 6)
+		status = gen7_check_mailbox_status(dev_priv);
+	else
+		status = gen6_check_mailbox_status(dev_priv);
+
+	if (status) {
+		DRM_DEBUG_DRIVER("warning: pcode (write) mailbox access failed: %d\n",
+				 status);
+		return status;
+	}
+
 	return 0;
 }