[PATCH] ppc64: SMU based macs cpufreq support

CPU freq support using 970FX powertune facility for iMac G5 and SMU
based single CPU desktop.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index b3e95ff0dba..ae1433da09b 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -604,6 +604,76 @@ _GLOBAL(real_writeb)
 #endif /* defined(CONFIG_PPC_PMAC) || defined(CONFIG_PPC_MAPLE) */
 
 /*
+ * SCOM access functions for 970 (FX only for now)
+ *
+ * unsigned long scom970_read(unsigned int address);
+ * void scom970_write(unsigned int address, unsigned long value);
+ *
+ * The address passed in is the 24 bits register address. This code
+ * is 970 specific and will not check the status bits, so you should
+ * know what you are doing.
+ */
+_GLOBAL(scom970_read)
+        /* interrupts off */
+        mfmsr   r4
+        ori     r0,r4,MSR_EE
+        xori    r0,r0,MSR_EE
+        mtmsrd  r0,1
+
+        /* rotate 24 bits SCOM address 8 bits left and mask out it's low 8 bits
+         * (including parity). On current CPUs they must be 0'd,
+         * and finally or in RW bit
+         */
+        rlwinm  r3,r3,8,0,15
+        ori     r3,r3,0x8000
+
+        /* do the actual scom read */
+        sync
+        mtspr   SPRN_SCOMC,r3
+        isync
+        mfspr   r3,SPRN_SCOMD
+        isync
+        mfspr   r0,SPRN_SCOMC
+        isync
+
+        /* XXX: fixup result on some buggy 970's (ouch ! we lost a bit, bah
+         * that's the best we can do). Not implemented yet as we don't use
+         * the scom on any of the bogus CPUs yet, but may have to be done
+         * ultimately
+         */
+
+        /* restore interrupts */
+        mtmsrd  r4,1
+        blr
+
+
+_GLOBAL(scom970_write)
+        /* interrupts off */
+        mfmsr   r5
+        ori     r0,r5,MSR_EE
+        xori    r0,r0,MSR_EE
+        mtmsrd  r0,1
+
+        /* rotate 24 bits SCOM address 8 bits left and mask out it's low 8 bits
+         * (including parity). On current CPUs they must be 0'd.
+         */
+
+        rlwinm  r3,r3,8,0,15
+
+        sync
+        mtspr   SPRN_SCOMD,r4      /* write data */
+        isync
+        mtspr   SPRN_SCOMC,r3      /* write command */
+        isync
+        mfspr   3,SPRN_SCOMC
+        isync
+
+        /* restore interrupts */
+        mtmsrd  r5,1
+        blr
+
+
+/*
  * Create a kernel thread
  *   kernel_thread(fn, arg, flags)
  */