3 files changed, 42 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/powermac/feature.c b/arch/powerpc/platforms/powermac/feature.c
index ba931be2175c..5169ecc37123 100644
--- a/arch/powerpc/platforms/powermac/feature.c
+++ b/arch/powerpc/platforms/powermac/feature.c
@@ -2565,6 +2565,8 @@ static void __init probe_uninorth(void)
 
         /* 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 @@ static void __init probe_uninorth(void)
                 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)
@@ -3029,3 +3033,8 @@ void pmac_resume_agp_for_card(struct pci_dev *dev)
         pmac_agp_resume(pmac_agp_bridge);
 }
 EXPORT_SYMBOL(pmac_resume_agp_for_card);
+
+int pmac_get_uninorth_variant(void)
+{
+        return uninorth_maj;
+}
diff --git a/drivers/macintosh/smu.c b/drivers/macintosh/smu.c
index 8ba49385c3ff..77ad192962c5 100644
--- a/drivers/macintosh/smu.c
+++ b/drivers/macintosh/smu.c
@@ -85,6 +85,7 @@ struct smu_device {
         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 @@ static void smu_start_cmd(void)
         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 @@ static irqreturn_t smu_db_intr(int irq, void *arg)
         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 @@ int __init smu_init (void)
         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");
@@ -533,6 +551,11 @@ int __init smu_init (void)
                 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;
 
diff --git a/include/asm-powerpc/pmac_feature.h b/include/asm-powerpc/pmac_feature.h
index 26bcb0aa164a..877c35a4356e 100644
--- a/include/asm-powerpc/pmac_feature.h
+++ b/include/asm-powerpc/pmac_feature.h
@@ -392,6 +392,14 @@ extern u32 __iomem *uninorth_base;
 #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__ */