powerpc/powernv: Add OPAL takeover from PowerVM

On machines supporting the OPAL firmware version 1, the system
is initially booted under pHyp. We then use a special hypercall
to verify if OPAL is available and if it is, we then trigger
a "takeover" which disables pHyp and loads the OPAL runtime
firmware, giving control to the kernel in hypervisor mode.

This patch add the necessary code to detect that the OPAL takeover
capability is present when running under PowerVM (aka pHyp) and
perform said takeover to get hypervisor control of the processor.

To perform the takeover, we must first use RTAS (within Open
Firmware runtime environment) to start all processors & threads,
in order to give control to OPAL on all of them. We then call
the takeover hypercall on everybody, OPAL will re-enter the kernel
main entry point passing it a flat device-tree.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 141 insertions, 1 deletions

diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
index 1c4325056b8..497133027ae 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -1,2 +1,2 @@
-obj-y                   += setup.o
+obj-y                   += setup.o opal-takeover.o
 obj-$(CONFIG_SMP)       += smp.o
diff --git a/arch/powerpc/platforms/powernv/opal-takeover.S b/arch/powerpc/platforms/powernv/opal-takeover.S
new file mode 100644
index 00000000000..77b48b2b930
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/opal-takeover.S
@@ -0,0 +1,140 @@
+/*
+ * PowerNV OPAL takeover assembly code, for use by prom_init.c
+ *
+ * Copyright 2011 IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/ppc_asm.h>
+#include <asm/hvcall.h>
+#include <asm/asm-offsets.h>
+#include <asm/opal.h>
+
+#define STK_PARAM(i)    (48 + ((i)-3)*8)
+
+#define H_HAL_TAKEOVER                  0x5124
+#define H_HAL_TAKEOVER_QUERY_MAGIC      -1
+
+        .text
+_GLOBAL(opal_query_takeover)
+        mfcr    r0
+        stw     r0,8(r1)
+        std     r3,STK_PARAM(r3)(r1)
+        std     r4,STK_PARAM(r4)(r1)
+        li      r3,H_HAL_TAKEOVER
+        li      r4,H_HAL_TAKEOVER_QUERY_MAGIC
+        HVSC
+        ld      r10,STK_PARAM(r3)(r1)
+        std     r4,0(r10)
+        ld      r10,STK_PARAM(r4)(r1)
+        std     r5,0(r10)
+        lwz     r0,8(r1)
+        mtcrf   0xff,r0
+        blr
+
+_GLOBAL(opal_do_takeover)
+        mfcr    r0
+        stw     r0,8(r1)
+        mflr    r0
+        std     r0,16(r1)
+        bl      __opal_do_takeover
+        ld      r0,16(r1)
+        mtlr    r0
+        lwz     r0,8(r1)
+        mtcrf   0xff,r0
+        blr
+
+__opal_do_takeover:
+        ld      r4,0(r3)
+        ld      r5,0x8(r3)
+        ld      r6,0x10(r3)
+        ld      r7,0x18(r3)
+        ld      r8,0x20(r3)
+        ld      r9,0x28(r3)
+        ld      r10,0x30(r3)
+        ld      r11,0x38(r3)
+        li      r3,H_HAL_TAKEOVER
+        HVSC
+        blr
+
+        .globl opal_secondary_entry
+opal_secondary_entry:
+        mr      r31,r3
+        mfmsr   r11
+        li      r12,(MSR_SF | MSR_ISF)@highest
+        sldi    r12,r12,48
+        or      r11,r11,r12
+        mtmsrd  r11
+        isync
+        mfspr   r4,SPRN_PIR
+        std     r4,0(r3)
+1:      HMT_LOW
+        ld      r4,8(r3)
+        cmpli   cr0,r4,0
+        beq     1b
+        HMT_MEDIUM
+1:      addi    r3,r31,16
+        bl      __opal_do_takeover
+        b       1b
+
+_GLOBAL(opal_enter_rtas)
+        mflr    r0
+        std     r0,16(r1)
+        stdu    r1,-PROM_FRAME_SIZE(r1) /* Save SP and create stack space */
+
+        /* Because PROM is running in 32b mode, it clobbers the high order half
+         * of all registers that it saves.  We therefore save those registers
+         * PROM might touch to the stack.  (r0, r3-r13 are caller saved)
+        */
+        SAVE_GPR(2, r1)
+        SAVE_GPR(13, r1)
+        SAVE_8GPRS(14, r1)
+        SAVE_10GPRS(22, r1)
+        mfcr    r10
+        mfmsr   r11
+        std     r10,_CCR(r1)
+        std     r11,_MSR(r1)
+
+        /* Get the PROM entrypoint */
+        mtlr    r5
+
+        /* Switch MSR to 32 bits mode
+         */
+        li      r12,1
+        rldicr  r12,r12,MSR_SF_LG,(63-MSR_SF_LG)
+        andc    r11,r11,r12
+        li      r12,1
+        rldicr  r12,r12,MSR_ISF_LG,(63-MSR_ISF_LG)
+        andc    r11,r11,r12
+        mtmsrd  r11
+        isync
+
+        /* Enter RTAS here... */
+        blrl
+
+        /* Just make sure that r1 top 32 bits didn't get
+         * corrupt by OF
+         */
+        rldicl  r1,r1,0,32
+
+        /* Restore the MSR (back to 64 bits) */
+        ld      r0,_MSR(r1)
+        MTMSRD(r0)
+        isync
+
+        /* Restore other registers */
+        REST_GPR(2, r1)
+        REST_GPR(13, r1)
+        REST_8GPRS(14, r1)
+        REST_10GPRS(22, r1)
+        ld      r4,_CCR(r1)
+        mtcr    r4
+
+        addi    r1,r1,PROM_FRAME_SIZE
+        ld      r0,16(r1)
+        mtlr    r0
+        blr