[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>

2 files changed, 81 insertions, 1 deletions

diff --git a/arch/ppc64/Kconfig b/arch/ppc64/Kconfig
index 2130cc315957..94a81279deac 100644
--- a/arch/ppc64/Kconfig
+++ b/arch/ppc64/Kconfig
@@ -173,6 +173,16 @@ config KEXEC
           support.  As of this writing the exact hardware interface is
           strongly in flux, so no good recommendation can be made.
 
+source "drivers/cpufreq/Kconfig"
+
+config CPU_FREQ_PMAC64
+        bool "Support for some Apple G5s"
+        depends on CPU_FREQ && PMAC_SMU && PPC64
+        select CPU_FREQ_TABLE
+        help
+          This adds support for frequency switching on Apple iMac G5,
+          and some of the more recent desktop G5 machines as well.
+
 config IBMVIO
         depends on PPC_PSERIES || PPC_ISERIES
         bool
diff --git a/arch/ppc64/kernel/misc.S b/arch/ppc64/kernel/misc.S
index 077507ffbab8..914632ec587d 100644
--- a/arch/ppc64/kernel/misc.S
+++ b/arch/ppc64/kernel/misc.S
@@ -560,7 +560,7 @@ _GLOBAL(real_readb)
         isync
         blr
 
-        /*
+/*
  * Do an IO access in real mode
  */
 _GLOBAL(real_writeb)
@@ -593,6 +593,76 @@ _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)
  */