x86: OLPC: add support for calling into OpenFirmware (v2)

PATCH In review Andres Salomon 2 participants 2 messages Jun 10, 2010 x86

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Andres Salomon

author

2010-06-10 04:14 UTC #0 lore raw

PATCH 1/1 x86: OLPC: add support for calling into OpenFirmware (v2)

Add support for saving OFW's cif, and later calling into it to run OFW commands. OFW remains resident in memory, living within virtual range 0xff800000 - 0xffc00000. A single page directory entry points to the pgdir that OFW actually uses, so rather than saving the entire page table, we save that one entry (and restore it for the call into OFW).

This is currently only used by the OLPC XO; however, there's nothing restricting OFW's usage on other (x86) platforms.

Signed-off-by Andres Salomon <[email protected]>

---
 arch/x86/Kconfig                |    9 ++++
 arch/x86/include/asm/olpc_ofw.h |   35 ++++++++++++++
 arch/x86/include/asm/setup.h    |    1 +
 arch/x86/kernel/Makefile        |    1 +
 arch/x86/kernel/head_32.S       |   34 ++++++++++++++
 arch/x86/kernel/olpc.c          |   12 ++---
 arch/x86/kernel/olpc_ofw.c      |   95 +++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/setup.c         |    4 ++
 8 files changed, 184 insertions(+), 7 deletions(-)
 create mode 100644 arch/x86/include/asm/olpc_ofw.h
 create mode 100644 arch/x86/kernel/olpc_ofw.c

arch/x86/Kconfig +9 -0

index dcb0593..71c194d 100644
@@ -2062,6 +2062,15 @@ config OLPC
 	  Add support for detecting the unique features of the OLPC
 	  XO hardware.
 
+config OLPC_OPENFIRMWARE
+	bool "Support for OLPC's Open Firmware"
+	depends on !X86_64 && !X86_PAE
+	default y if OLPC
+	help
+	  This option adds support for the implementation of Open Firmware
+	  that is used on the OLPC XO-1 Children's Machine.
+	  If unsure, say N here.
+
 endif # X86_32
 
 config K8_NB

arch/x86/include/asm/olpc_ofw.h new file +35 -0

new file mode 100644
index 0000000..7a16734
@@ -0,0 +1,35 @@
+#ifndef _ASM_X86_OLPC_OFW_H
+#define _ASM_X86_OLPC_OFW_H
+
+/* index into the page table containing the entry OFW occupies */
+#define OLPC_OFW_PDE_NR 1022
+
+#ifdef CONFIG_OLPC_OPENFIRMWARE
+
+#ifndef __ASSEMBLY__
+
+/* address of OFW callback interface; will be NULL if OFW isn't found */
+extern int (*olpc_ofw_cif)(int *);
+
+/* page dir entry containing OFW's current memory */
+extern pgdval_t olpc_ofw_pgd;
+
+/* run an OFW command by calling into the firmware */
+#define olpc_ofw(name, args, res) \
+	__olpc_ofw((name), ARRAY_SIZE(args), args, ARRAY_SIZE(res), res)
+
+extern int __olpc_ofw(const char *name, int nr_args, void **args, int nr_res,
+		void **res);
+
+/* determine/ensure OFW lives in the proper place in (virtual) memory */
+extern void olpc_ofw_detect_range(void);
+
+#endif /* !__ASSEMBLY__ */
+
+#else /* !CONFIG_OLPC_OPENFIRMWARE */
+
+static inline void olpc_ofw_detect_range(void) { }
+
+#endif /* !CONFIG_OLPC_OPENFIRMWARE */
+
+#endif /* _ASM_X86_OLPC_OFW_H */

arch/x86/include/asm/setup.h +1 -0

index 86b1506..5cba9eb 100644
@@ -21,6 +21,7 @@
 #define OLD_CL_MAGIC		0xA33F
 #define OLD_CL_ADDRESS		0x020	/* Relative to real mode data */
 #define NEW_CL_POINTER		0x228	/* Relative to real mode data */
+#define OLPC_OFW_INFO_OFFSET	0xB0	/* Relative to real mode data */
 
 #ifndef __ASSEMBLY__
 #include <asm/bootparam.h>

arch/x86/kernel/Makefile +1 -0

index e77b220..0925676 100644
@@ -104,6 +104,7 @@ obj-$(CONFIG_SCx200)		+= scx200.o
 scx200-y			+= scx200_32.o
 
 obj-$(CONFIG_OLPC)		+= olpc.o
+obj-$(CONFIG_OLPC_OPENFIRMWARE)	+= olpc_ofw.o
 obj-$(CONFIG_X86_MRST)		+= mrst.o
 
 microcode-y				:= microcode_core.o

arch/x86/kernel/head_32.S +34 -0

index 37c3d4b..40cf275 100644
@@ -17,6 +17,7 @@
 #include <asm/thread_info.h>
 #include <asm/asm-offsets.h>
 #include <asm/setup.h>
+#include <asm/olpc_ofw.h>
 #include <asm/processor-flags.h>
 #include <asm/msr-index.h>
 #include <asm/cpufeature.h>

@@ -131,6 +132,31 @@ ENTRY(startup_32)
 	movsl
 1:
 
+#ifdef CONFIG_OLPC_OPENFIRMWARE
+	movl $0x0, pa(olpc_ofw_cif)
+
+	/* Did OpenFirmware boot us? */
+	movl $pa(boot_params) + OLPC_OFW_INFO_OFFSET, %ebp
+	cmpl $0x2057464F, (%ebp)	/* Magic number "OFW " */
+	jne 3f
+
+	/* Save the callback address for calling into OFW from linux */
+	mov 0x8(%ebp), %eax
+	mov %eax, pa(olpc_ofw_cif)
+
+	/*
+	 * %cr3 holds OFW's pgdir table.  For calling info OFW, we need to
+	 * the save next-to-last pgdir table entry, which points to a page
+	 * table that lives within OFW's memory.  The pgdir table contains
+	 * 1024 entries (each a 4 byte pde), so we want
+	 * ((int *) %cr3)[OLPC_OFW_PDE_NR].
+	 */
+	movl %cr3, %eax
+	movl OLPC_OFW_PDE_NR*4(%eax), %ebx
+	movl %ebx, pa(olpc_ofw_pgd)
+3:
+#endif
+
 #ifdef CONFIG_PARAVIRT
 	/* This is can only trip for a broken bootloader... */
 	cmpw $0x207, pa(boot_params + BP_version)

@@ -658,6 +684,14 @@ ENTRY(stack_start)
 	.long init_thread_union+THREAD_SIZE
 	.long __BOOT_DS
 
+.globl olpc_ofw_cif
+.globl olpc_ofw_pgd
+
+olpc_ofw_cif:
+	.long olpc_ofw_cif
+olpc_ofw_pgd:
+	.long olpc_ofw_pgd
+
 ready:	.byte 0
 
 early_recursion_flag:

arch/x86/kernel/olpc.c +5 -7

index 8297160..1566052 100644
@@ -21,10 +21,7 @@
 #include <asm/geode.h>
 #include <asm/setup.h>
 #include <asm/olpc.h>
-
-#ifdef CONFIG_OPEN_FIRMWARE
-#include <asm/ofw.h>
-#endif
+#include <asm/olpc_ofw.h>
 
 struct olpc_platform_t olpc_platform_info;
 EXPORT_SYMBOL_GPL(olpc_platform_info);

@@ -188,14 +185,15 @@ err:
 }
 EXPORT_SYMBOL_GPL(olpc_ec_cmd);
 
-#ifdef CONFIG_OPEN_FIRMWARE
+#ifdef CONFIG_OLPC_OPENFIRMWARE
 static void __init platform_detect(void)
 {
 	size_t propsize;
 	__be32 rev;
+	void *args[] = { NULL, "board-revision-int", &rev, (void *)4 };
+	void *res[] = { &propsize };
 
-	if (ofw("getprop", 4, 1, NULL, "board-revision-int", &rev, 4,
-			&propsize) || propsize != 4) {
+	if (olpc_ofw("getprop", args, res) || propsize != 4) {
 		printk(KERN_ERR "ofw: getprop call failed!\n");
 		rev = cpu_to_be32(0);
 	}

arch/x86/kernel/olpc_ofw.c new file +95 -0

95 lines not on this page · raw message

arch/x86/kernel/setup.c +4 -0

index b4ae4ac..67e98c3 100644
@@ -102,6 +102,7 @@
 
 #include <asm/paravirt.h>
 #include <asm/hypervisor.h>
+#include <asm/olpc_ofw.h>
 
 #include <asm/percpu.h>
 #include <asm/topology.h>

@@ -736,6 +737,9 @@ void __init setup_arch(char **cmdline_p)
 	/* VMI may relocate the fixmap; do this before touching ioremap area */
 	vmi_init();
 
+	/* OFW also may relocate the fixmap */
+	olpc_ofw_detect_range();
+
 	early_trap_init();
 	early_cpu_init();
 	early_ioremap_init();

Signature · 1 line

1.5.6.5

H. Peter Anvin

reviewer

2010-06-10 04:36 UTC #1 lore raw

Quoted 9 lines · Andres Salomon

Add support for saving OFW's cif, and later calling into it to run OFW commands. OFW remains resident in memory, living within virtual range 0xff800000 - 0xffc00000. A single page directory entry points to the pgdir that OFW actually uses, so rather than saving the entire page table, we save that one entry (and restore it for the call into OFW).
This is currently only used by the OLPC XO; however, there's nothing restricting OFW's usage on other (x86) platforms.

... well, except for the fact that the protocol is insane, and not used by anything else ...

arch/x86/include/asm/setup.h line 24

Quoted 9 lines

arch/x86/include/asm/setup.h +1 -0

index 86b1506..5cba9eb 100644
@@ -21,6 +21,7 @@
 #define OLD_CL_MAGIC		0xA33F
 #define OLD_CL_ADDRESS		0x020	/* Relative to real mode data */
 #define NEW_CL_POINTER		0x228	/* Relative to real mode data */
+#define OLPC_OFW_INFO_OFFSET	0xB0	/* Relative to real mode data */

This should be added to struct boot_params as well as the various documentation files. I note also that this interrupts one of the largest available spans we have in this structure, but I guess there is very little that can be done about that.

arch/x86/include/asm/setup.h line 27

Quoted 3 lines

arch/x86/include/asm/setup.h +3 -0

+#ifdef CONFIG_OLPC_OPENFIRMWARE
+	movl $0x0, pa(olpc_ofw_cif)
+

We just cleared BSS -- there is no point in doing this.

arch/x86/include/asm/setup.h

Quoted 5 lines

arch/x86/include/asm/setup.h +5 -0

+	/* Did OpenFirmware boot us? */
+	movl $pa(boot_params) + OLPC_OFW_INFO_OFFSET, %ebp
+	cmpl $0x2057464F, (%ebp)	/* Magic number "OFW " */
+	jne 3f
+

This stuff is in high memory, or otherwise protected in the memory map, no? If so, there is absolutely no point in doing this this early; it can be done in C code just fine. The only thing that needs to be done is to same the value of %cr3 on entry (and not even the offset value of %cr3).

arch/x86/include/asm/setup.h

Quoted 3 lines

arch/x86/include/asm/setup.h +3 -0

+	/* Save the callback address for calling into OFW from linux */
+	mov 0x8(%ebp), %eax
+	mov %eax, pa(olpc_ofw_cif)

Again, please put the definition of the entire structure into struct boot_params as well as in the relevant documentation files.

It's really too bad that you didn't re-use the location used for struct efi_info since that is mutually exclusive and has a signature.

I won't pick on you for not using the platform ID since that is a rather new invention, but it would have been beneficial rather than ad hoc inventions all along...

Quoted 13 lines

arch/x86/include/asm/setup.h +13 -0

+/* setup and do actual call into OFW */
+static int setup_ofw(int *ofw_args)
+{
+	pgd_t *base, *pde;
+	pgdval_t oldval;
+	int ret;
+
+	/* temporarily clobber %cr3[OLPC_OFW_PDE_NR] w/ olpc_ofw_pgd */
+	base = __va(read_cr3());
+	pde = &base[OLPC_OFW_PDE_NR];
+	oldval = pgd_val(*pde);
+	set_pgd(pde, __pgd(olpc_ofw_pgd));
+	flush_tlb();

arch/x86/include/asm/setup.h

Quoted 10 lines

arch/x86/include/asm/setup.h +10 -0

+
+	/* call into ofw */
+	ret = olpc_ofw_cif(ofw_args);
+
+	/* restore %cr3[OLPC_OFW_PDE_NR] */
+	set_pgd(pde, __pgd(oldval));
+	flush_tlb();
+
+	return ret;
+}

Why are you still mucking around with swapping %cr3s? Once you have claimed top of the virtual address space, you can install your PGD permanently.

-hpa

Signature · 2 lines

H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.