diff --git a/sys/powerpc/include/spr.h b/sys/powerpc/include/spr.h
index 216a3bbd3559..721782e90f36 100644
--- a/sys/powerpc/include/spr.h
+++ b/sys/powerpc/include/spr.h
@@ -412,6 +412,19 @@
 #define	SPR_MD_RAM0		0x339	/* ..8 IMMU RAM entry read reg 0 */
 #define	SPR_MD_RAM1		0x33a	/* ..8 IMMU RAM entry read reg 1 */
 #define	SPR_PSSCR		0x357	/* Processor Stop Status and Control Register (ISA 3.0) */
+#define	  PSSCR_PLS_S		  60
+#define	  PSSCR_PLS_M		  (0xf << PSSCR_PLS_S)
+#define	  PSSCR_SD		  (1 << 22)
+#define	  PSSCR_ESL		  (1 << 21)
+#define	  PSSCR_EC		  (1 << 20)
+#define	  PSSCR_PSLL_S		  16
+#define	  PSSCR_PSLL_M		  (0xf << PSSCR_PSLL_S)
+#define	  PSSCR_TR_S		  8
+#define	  PSSCR_TR_M		  (0x3 << PSSCR_TR_S)
+#define	  PSSCR_MTL_S		  4
+#define	  PSSCR_MTL_M		  (0xf << PSSCR_MTL_S)
+#define	  PSSCR_RL_S		  0
+#define	  PSSCR_RL_M		  (0xf << PSSCR_RL_S)
 #define	SPR_PMCR                0x374   /* Processor Management Control Register */
 #define	SPR_UMMCR2		0x3a0	/* .6. User Monitor Mode Control Register 2 */
 #define	SPR_UMMCR0		0x3a8	/* .6. User Monitor Mode Control Register 0 */
diff --git a/sys/powerpc/powerpc/cpu.c b/sys/powerpc/powerpc/cpu.c
index 8d54593cc32c..0013864f9077 100644
--- a/sys/powerpc/powerpc/cpu.c
+++ b/sys/powerpc/powerpc/cpu.c
@@ -787,7 +787,6 @@ cpu_idle_booke(sbintime_t sbt)
 static void
 cpu_idle_powerx(sbintime_t sbt)
 {
-
 	/* Sleeping when running on one cpu gives no advantages - avoid it */
 	if (smp_started == 0)
 		return;
@@ -816,7 +815,8 @@ cpu_idle_power9(sbintime_t sbt)
 	/* Suspend external interrupts until stop instruction completes. */
 	mtmsr(msr &  ~PSL_EE);
 	/* Set the stop state to lowest latency, wake up to next instruction */
-	mtspr(SPR_PSSCR, 0);
+	/* Set maximum transition level to 2, for deepest lossless sleep. */
+	mtspr(SPR_PSSCR, (2 << PSSCR_MTL_S) | (0 << PSSCR_RL_S));
 	/* "stop" instruction (PowerISA 3.0) */
 	__asm __volatile (".long 0x4c0002e4");
 	/*