drm/i915: Handle catastrophic error on engine reset

If cat error is set, we need to clear it by acking it. Further,
if it is set, we must not do a normal request for reset.

v2: avoid goto (Chris)
v3: comment, error format, direct assign (Chris)
Bspec: 12567
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190412165353.16432-1-mika.kuoppala@linux.intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -2446,8 +2446,10 @@ enum i915_power_well_id {
 #define RING_HWS_PGA(base)	_MMIO((base) + 0x80)
 #define RING_HWS_PGA_GEN6(base)	_MMIO((base) + 0x2080)
 #define RING_RESET_CTL(base)	_MMIO((base) + 0xd0)
-#define   RESET_CTL_REQUEST_RESET  (1 << 0)
-#define   RESET_CTL_READY_TO_RESET (1 << 1)
+#define   RESET_CTL_CAT_ERROR	   REG_BIT(2)
+#define   RESET_CTL_READY_TO_RESET REG_BIT(1)
+#define   RESET_CTL_REQUEST_RESET  REG_BIT(0)
+
 #define RING_SEMA_WAIT_POLL(base) _MMIO((base) + 0x24c)
 
 #define HSW_GTT_CACHE_EN	_MMIO(0x4024)

drivers/gpu/drm/i915/i915_reset.c

@@ -495,7 +495,17 @@ static int gen8_engine_reset_prepare(struct intel_engine_cs *engine)
 	int ret;
 
 	ack = intel_uncore_read_fw(uncore, reg);
-	if (!(ack & RESET_CTL_READY_TO_RESET)) {
+	if (ack & RESET_CTL_CAT_ERROR) {
+		/*
+		 * For catastrophic errors, ready-for-reset sequence
+		 * needs to be bypassed: HAS#396813
+		 */
+		request = RESET_CTL_CAT_ERROR;
+		mask = RESET_CTL_CAT_ERROR;
+
+		/* Catastrophic errors need to be cleared by HW */
+		ack = 0;
+	} else if (!(ack & RESET_CTL_READY_TO_RESET)) {
 		request = RESET_CTL_REQUEST_RESET;
 		mask = RESET_CTL_READY_TO_RESET;
 		ack = RESET_CTL_READY_TO_RESET;