[POWERPC] Disable G5 NAP mode during SMU commands on U3

It appears that with the U3 northbridge, if the processor is in NAP mode the whole time while waiting for an SMU command to complete, then the SMU will fail. It could be related to the weird backward mechanism the SMU uses to get to system memory via i2c to the northbridge that doesn't operate properly when the said bridge is in napping along with the CPU. That is on U3 at least, U4 doesn't seem to be affected. This didn't show before NO_HZ as the timer wakeup was enough to make it work it seems, but that is no longer the case. This fixes it by disabling NAP mode on those machines while an SMU command is in flight. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Paul Mackerras <paulus@samba.org>

[POWERPC] Disable G5 NAP mode during SMU commands on U3
It appears that with the U3 northbridge, if the processor is in NAP mode the whole time while waiting for an SMU command to complete, then the SMU will fail. It could be related to the weird backward mechanism the SMU uses to get to system memory via i2c to the northbridge that doesn't operate properly when the said bridge is in napping along with the CPU. That is on U3 at least, U4 doesn't seem to be affected. This didn't show before NO_HZ as the timer wakeup was enough to make it work it seems, but that is no longer the case. This fixes it by disabling NAP mode on those machines while an SMU command is in flight. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
Benjamin Herrenschmidt · Paul Mackerras
1 parent a4ffc0a0b2
Showing 3 changed files with 42 additions and 2 deletions Side-by-side Diff
arch/powerpc/platforms/powermac/feature.c
drivers/macintosh/smu.c
include/asm-powerpc/pmac_feature.h
@@ -2565,6 +2565,8 @@
  
 	/* Locate core99 Uni-N */
 	uninorth_node = of_find_node_by_name(NULL, "uni-n");
+	uninorth_maj = 1;
+
 	/* Locate G5 u3 */
 	if (uninorth_node == NULL) {
 		uninorth_node = of_find_node_by_name(NULL, "u3");
  
@@ -2575,8 +2577,10 @@
 		uninorth_node = of_find_node_by_name(NULL, "u4");
 		uninorth_maj = 4;
 	}
-	if (uninorth_node == NULL)
+	if (uninorth_node == NULL) {
+		uninorth_maj = 0;
 		return;
+	}
  
 	addrp = of_get_property(uninorth_node, "reg", NULL);
 	if (addrp == NULL)
@@ -3029,4 +3033,9 @@
 	pmac_agp_resume(pmac_agp_bridge);
 }
 EXPORT_SYMBOL(pmac_resume_agp_for_card);
+
+int pmac_get_uninorth_variant(void)
+{
+	return uninorth_maj;
+}
@@ -85,6 +85,7 @@
 	u32			cmd_buf_abs;	/* command buffer absolute */
 	struct list_head	cmd_list;
 	struct smu_cmd		*cmd_cur;	/* pending command */
+	int			broken_nap;
 	struct list_head	cmd_i2c_list;
 	struct smu_i2c_cmd	*cmd_i2c_cur;	/* pending i2c command */
 	struct timer_list	i2c_timer;
@@ -135,6 +136,19 @@
 	fend = faddr + smu->cmd_buf->length + 2;
 	flush_inval_dcache_range(faddr, fend);
  
+
+	/* We also disable NAP mode for the duration of the command
+	 * on U3 based machines.
+	 * This is slightly racy as it can be written back to 1 by a sysctl
+	 * but that never happens in practice. There seem to be an issue with
+	 * U3 based machines such as the iMac G5 where napping for the
+	 * whole duration of the command prevents the SMU from fetching it
+	 * from memory. This might be related to the strange i2c based
+	 * mechanism the SMU uses to access memory.
+	 */
+	if (smu->broken_nap)
+		powersave_nap = 0;
+
 	/* This isn't exactly a DMA mapping here, I suspect
 	 * the SMU is actually communicating with us via i2c to the
 	 * northbridge or the CPU to access RAM.
@@ -211,6 +225,10 @@
 	misc = cmd->misc;
 	mb();
 	cmd->status = rc;
+
+	/* Re-enable NAP mode */
+	if (smu->broken_nap)
+		powersave_nap = 1;
  bail:
 	/* Start next command if any */
 	smu_start_cmd();
@@ -461,7 +479,7 @@
         if (np == NULL)
 		return -ENODEV;
  
-	printk(KERN_INFO "SMU driver %s %s\n", VERSION, AUTHOR);
+	printk(KERN_INFO "SMU: Driver %s %s\n", VERSION, AUTHOR);
  
 	if (smu_cmdbuf_abs == 0) {
 		printk(KERN_ERR "SMU: Command buffer not allocated !\n");
@@ -532,6 +550,11 @@
 		printk(KERN_ERR "SMU: Can't map doorbell buffer pointer !\n");
 		goto fail;
 	}
+
+	/* U3 has an issue with NAP mode when issuing SMU commands */
+	smu->broken_nap = pmac_get_uninorth_variant() < 4;
+	if (smu->broken_nap)
+		printk(KERN_INFO "SMU: using NAP mode workaround\n");
  
 	sys_ctrler = SYS_CTRLER_SMU;
 	return 0;
@@ -392,6 +392,14 @@
 #define UN_BIS(r,v)	(UN_OUT((r), UN_IN(r) | (v)))
 #define UN_BIC(r,v)	(UN_OUT((r), UN_IN(r) & ~(v)))
  
+/* Uninorth variant:
+ *
+ * 0 = not uninorth
+ * 1 = U1.x or U2.x
+ * 3 = U3
+ * 4 = U4
+ */
+extern int pmac_get_uninorth_variant(void);
  
 #endif /* __ASM_POWERPC_PMAC_FEATURE_H */
 #endif /* __KERNEL__ */
...	...	@@ -2565,6 +2565,8 @@
2565	2565
2566	2566	/* Locate core99 Uni-N */
2567	2567	uninorth_node = of_find_node_by_name(NULL, "uni-n");
	2568	+ uninorth_maj = 1;
	2569	+
2568	2570	/* Locate G5 u3 */
2569	2571	if (uninorth_node == NULL) {
2570	2572	uninorth_node = of_find_node_by_name(NULL, "u3");
2571	2573
...	...	@@ -2575,8 +2577,10 @@
2575	2577	uninorth_node = of_find_node_by_name(NULL, "u4");
2576	2578	uninorth_maj = 4;
2577	2579	}
2578		- if (uninorth_node == NULL)
	2580	+ if (uninorth_node == NULL) {
	2581	+ uninorth_maj = 0;
2579	2582	return;
	2583	+ }
2580	2584
2581	2585	addrp = of_get_property(uninorth_node, "reg", NULL);
2582	2586	if (addrp == NULL)
...	...	@@ -3029,4 +3033,9 @@
3029	3033	pmac_agp_resume(pmac_agp_bridge);
3030	3034	}
3031	3035	EXPORT_SYMBOL(pmac_resume_agp_for_card);
	3036	+
	3037	+int pmac_get_uninorth_variant(void)
	3038	+{
	3039	+ return uninorth_maj;
	3040	+}
...	...	@@ -85,6 +85,7 @@
85	85	u32 cmd_buf_abs; /* command buffer absolute */
86	86	struct list_head cmd_list;
87	87	struct smu_cmd cmd_cur; / pending command */
	88	+ int broken_nap;
88	89	struct list_head cmd_i2c_list;
89	90	struct smu_i2c_cmd cmd_i2c_cur; / pending i2c command */
90	91	struct timer_list i2c_timer;
...	...	@@ -135,6 +136,19 @@
135	136	fend = faddr + smu->cmd_buf->length + 2;
136	137	flush_inval_dcache_range(faddr, fend);
137	138
	139	+
	140	+ /* We also disable NAP mode for the duration of the command
	141	+ * on U3 based machines.
	142	+ * This is slightly racy as it can be written back to 1 by a sysctl
	143	+ * but that never happens in practice. There seem to be an issue with
	144	+ * U3 based machines such as the iMac G5 where napping for the
	145	+ * whole duration of the command prevents the SMU from fetching it
	146	+ * from memory. This might be related to the strange i2c based
	147	+ * mechanism the SMU uses to access memory.
	148	+ */
	149	+ if (smu->broken_nap)
	150	+ powersave_nap = 0;
	151	+
138	152	/* This isn't exactly a DMA mapping here, I suspect
139	153	* the SMU is actually communicating with us via i2c to the
140	154	* northbridge or the CPU to access RAM.
...	...	@@ -211,6 +225,10 @@
211	225	misc = cmd->misc;
212	226	mb();
213	227	cmd->status = rc;
	228	+
	229	+ /* Re-enable NAP mode */
	230	+ if (smu->broken_nap)
	231	+ powersave_nap = 1;
214	232	bail:
215	233	/* Start next command if any */
216	234	smu_start_cmd();
...	...	@@ -461,7 +479,7 @@
461	479	if (np == NULL)
462	480	return -ENODEV;
463	481
464		- printk(KERN_INFO "SMU driver %s %s\n", VERSION, AUTHOR);
	482	+ printk(KERN_INFO "SMU: Driver %s %s\n", VERSION, AUTHOR);
465	483
466	484	if (smu_cmdbuf_abs == 0) {
467	485	printk(KERN_ERR "SMU: Command buffer not allocated !\n");
...	...	@@ -532,6 +550,11 @@
532	550	printk(KERN_ERR "SMU: Can't map doorbell buffer pointer !\n");
533	551	goto fail;
534	552	}
	553	+
	554	+ /* U3 has an issue with NAP mode when issuing SMU commands */
	555	+ smu->broken_nap = pmac_get_uninorth_variant() < 4;
	556	+ if (smu->broken_nap)
	557	+ printk(KERN_INFO "SMU: using NAP mode workaround\n");
535	558
536	559	sys_ctrler = SYS_CTRLER_SMU;
537	560	return 0;
...	...	@@ -392,6 +392,14 @@
392	392	#define UN_BIS(r,v) (UN_OUT((r), UN_IN(r) \| (v)))
393	393	#define UN_BIC(r,v) (UN_OUT((r), UN_IN(r) & ~(v)))
394	394
	395	+/* Uninorth variant:
	396	+ *
	397	+ * 0 = not uninorth
	398	+ * 1 = U1.x or U2.x
	399	+ * 3 = U3
	400	+ * 4 = U4
	401	+ */
	402	+extern int pmac_get_uninorth_variant(void);
395	403
396	404	#endif /* __ASM_POWERPC_PMAC_FEATURE_H */
397	405	#endif /* __KERNEL__ */