powerpc: Define differences between doorbells on book3e and book3s

There are a few key differences between doorbells on server compared
with embedded that we care about on Linux, namely:

- We have a new msgsndp instruction for directed privileged doorbells.
  msgsnd is used for directed hypervisor doorbells.
- The tag we use in the instruction is the Thread Identification
  Register of the recipient thread (since server doorbells can only
  occur between threads within a single core), and is only 7 bits wide.
- A new message type is introduced for server doorbells (none of the
  existing book3e message types are currently supported on book3s).

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Tested-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/dbell.c

@@ -21,7 +21,7 @@
 #ifdef CONFIG_SMP
 void doorbell_setup_this_cpu(void)
 {
-	unsigned long tag = mfspr(SPRN_PIR) & 0x3fff;
+	unsigned long tag = mfspr(SPRN_DOORBELL_CPUTAG) & PPC_DBELL_TAG_MASK;
 
 	smp_muxed_ipi_set_data(smp_processor_id(), tag);
 }
@@ -30,7 +30,7 @@ void doorbell_cause_ipi(int cpu, unsigned long data)
 {
 	/* Order previous accesses vs. msgsnd, which is treated as a store */
 	mb();
-	ppc_msgsnd(PPC_DBELL, 0, data);
+	ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, data);
 }
 
 void doorbell_exception(struct pt_regs *regs)