[OpenBIOS] [PATCH] ppc: don't use virtual image stack for startup context

[Mark Cave-Ayland]

Part of commit 070ea60 created a new stack within the virtual image for use by
the startup context. Unfortunately the current implementations of virt_to_phys()
as used by some drivers are incorrect which causes issues with some parts of
OpenBIOS, notably the USB stack.

Revert back to using the initial stack in start.S which ensures a 1:1 mapping
between virtual and physical addresses to avoid such problems.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland at ilande.co.uk>
---
 arch/ppc/qemu/context.c |    1 -
 arch/ppc/qemu/ldscript  |    6 +-----
 arch/ppc/qemu/start.S   |    6 ++++++
 include/arch/ppc/io.h   |    2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/ppc/qemu/context.c b/arch/ppc/qemu/context.c
index 18459b8..65cd4e4 100644
--- a/arch/ppc/qemu/context.c
+++ b/arch/ppc/qemu/context.c
@@ -41,7 +41,6 @@ void of_client_callback(void);
  * to start us up.
  */
 static struct context main_ctx = {
-    .sp = (unsigned long) &_estack - SAVE_SPACE,
     .pc = (unsigned long) start_main,
     .return_addr = (unsigned long) __exit_context,
 };
diff --git a/arch/ppc/qemu/ldscript b/arch/ppc/qemu/ldscript
index 11ebf4b..8027b39 100644
--- a/arch/ppc/qemu/ldscript
+++ b/arch/ppc/qemu/ldscript
@@ -51,11 +51,7 @@ SECTIONS
 	*(.bss)
 	*(.bss.*)
 	*(COMMON)
-	
-	_stack = .;
-	. += CSTACK_SIZE;
-	. = ALIGN(16);
-	_estack = .;
+	_ebss = .;
     }
 
     . = HRESET_ADDR;
diff --git a/arch/ppc/qemu/start.S b/arch/ppc/qemu/start.S
index 33ca1e0..fed1b55 100644
--- a/arch/ppc/qemu/start.S
+++ b/arch/ppc/qemu/start.S
@@ -482,6 +482,12 @@ real_entry:
 #endif
 
 	bl	BRANCH_LABEL(setup_mmu)
+
+	/* load stack pointer into context */
+	LOAD_REG_IMMEDIATE(r4, __context)
+	PPC_LL  r4, 0(r4)
+	PPC_STL r1, (2 * ULONG_SIZE)(r4)
+
 	bl	BRANCH_LABEL(__switch_context_nosave)
 1:	nop
 	b	1b
diff --git a/include/arch/ppc/io.h b/include/arch/ppc/io.h
index 39c60d7..3449c5b 100644
--- a/include/arch/ppc/io.h
+++ b/include/arch/ppc/io.h
@@ -6,7 +6,7 @@
 #define NO_QEMU_PROTOS
 #include "arch/common/fw_cfg.h"
 
-extern char _start, _end, _estack;
+extern char _start, _end;
 extern unsigned long virt_offset;
 
 #define phys_to_virt(phys) ((void *) ((unsigned long) (phys) - virt_offset))
-- 
1.7.10.4