1 files changed, 24 insertions, 1 deletions

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;