powerpc/powernv: Show checkstop reason for NPU2 HMIs

If the kernel is notified of an HMI caused by the NPU2, it's currently
not being recognized and it logs the default message:

    Unknown Malfunction Alert of type 3

The NPU on Power 9 has 3 Fault Isolation Registers, so that's a lot of
possible causes, but we should at least log that it's an NPU problem
and report which FIR and which bit were raised if opal gave us the
information.
Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/opal-api.h

@@ -568,6 +568,7 @@ enum OpalHMI_XstopType {
 	CHECKSTOP_TYPE_UNKNOWN	=	0,
 	CHECKSTOP_TYPE_CORE	=	1,
 	CHECKSTOP_TYPE_NX	=	2,
+	CHECKSTOP_TYPE_NPU	=	3
 };
 
 enum OpalHMI_CoreXstopReason {

arch/powerpc/platforms/powernv/opal-hmi.c

@@ -137,6 +137,43 @@ static void print_nx_checkstop_reason(const char *level,
 					xstop_reason[i].description);
 }
 
+static void print_npu_checkstop_reason(const char *level,
+					struct OpalHMIEvent *hmi_evt)
+{
+	uint8_t reason, reason_count, i;
+
+	/*
+	 * We may not have a checkstop reason on some combination of
+	 * hardware and/or skiboot version
+	 */
+	if (!hmi_evt->u.xstop_error.xstop_reason) {
+		printk("%s	NPU checkstop on chip %x\n", level,
+			be32_to_cpu(hmi_evt->u.xstop_error.u.chip_id));
+		return;
+	}
+
+	/*
+	 * NPU2 has 3 FIRs. Reason encoded on a byte as:
+	 *   2 bits for the FIR number
+	 *   6 bits for the bit number
+	 * It may be possible to find several reasons.
+	 *
+	 * We don't display a specific message per FIR bit as there
+	 * are too many and most are meaningless without the workbook
+	 * and/or hw team help anyway.
+	 */
+	reason_count = sizeof(hmi_evt->u.xstop_error.xstop_reason) /
+		sizeof(reason);
+	for (i = 0; i < reason_count; i++) {
+		reason = (hmi_evt->u.xstop_error.xstop_reason >> (8 * i)) & 0xFF;
+		if (reason)
+			printk("%s	NPU checkstop on chip %x: FIR%d bit %d is set\n",
+				level,
+				be32_to_cpu(hmi_evt->u.xstop_error.u.chip_id),
+				reason >> 6, reason & 0x3F);
+	}
+}
+
 static void print_checkstop_reason(const char *level,
 					struct OpalHMIEvent *hmi_evt)
 {
@@ -148,6 +185,9 @@ static void print_checkstop_reason(const char *level,
 	case CHECKSTOP_TYPE_NX:
 		print_nx_checkstop_reason(level, hmi_evt);
 		break;
+	case CHECKSTOP_TYPE_NPU:
+		print_npu_checkstop_reason(level, hmi_evt);
+		break;
 	default:
 		printk("%s	Unknown Malfunction Alert of type %d\n",
 		       level, type);