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From: Grant Likely <grant.likely@secretlab.ca>
To: linux-arm-kernel@lists.infradead.org
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>,
	Russell King <linux@arm.linux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	devicetree-discuss@lists.ozlabs.org,
	linux-kernel@vger.kernel.org, Olof Johansson <olof@lixom.net>,
	Jeremy Kerr <jeremy.kerr@canonical.com>,
	John Linn <John.Linn@xilinx.com>,
	Lennert Buijtenhek <buytenh@wantstofly.org>
Subject: [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image
Date: Tue, 18 Jan 2011 13:29:02 -0700	[thread overview]
Message-ID: <20110118202902.13011.68847.stgit@localhost6.localdomain6> (raw)
In-Reply-To: <20110118195933.13011.56098.stgit@localhost6.localdomain6>

The dtb is passed to the kernel via register r2, which is the same
method that is used to pass an atags pointer.  This patch modifies
__vet_atags to not clear r2 when it encounters a dtb image.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
---
 arch/arm/kernel/head-common.S |   19 +++++++++++++------
 arch/arm/kernel/head.S        |    8 ++++----
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 8f57515..d9a9105 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -14,6 +14,7 @@
 #define ATAG_CORE 0x54410001
 #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
 #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
+#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
 
 /*
  * Exception handling.  Something went wrong and we can't proceed.  We
@@ -105,22 +106,28 @@ __lookup_machine_type_data:
 
 /* Determine validity of the r2 atags pointer.  The heuristic requires
  * that the pointer be aligned, in the first 16k of physical RAM and
- * that the ATAG_CORE marker is first and present.  Future revisions
+ * that the ATAG_CORE marker is first and present.  If CONFIG_OF_FLATTREE
+ * is selected, then it will also accept a dtb pointer.  Future revisions
  * of this function may be more lenient with the physical address and
  * may also be able to move the ATAGS block if necessary.
  *
  * r8  = machinfo
  *
  * Returns:
- *  r2 either valid atags pointer, or zero
+ *  r2 either valid atags pointer, valid dtb pointer, or zero
  *  r5, r6 corrupted
  */
 __vet_atags:
 	tst	r2, #0x3			@ aligned?
 	bne	1f
 
-	ldr	r5, [r2, #0]			@ is first tag ATAG_CORE?
-	cmp	r5, #ATAG_CORE_SIZE
+#ifdef CONFIG_OF_FLATTREE
+	ldr	r5, [r2, #0]			@ is it a DTB?
+	ldr	r6, =OF_DT_MAGIC
+	cmp	r5, r6
+	beq	2f
+#endif
+	cmp	r5, #ATAG_CORE_SIZE		@ is first tag ATAG_CORE?
 	cmpne	r5, #ATAG_CORE_SIZE_EMPTY
 	bne	1f
 	ldr	r5, [r2, #4]
@@ -128,7 +135,7 @@ __vet_atags:
 	cmp	r5, r6
 	bne	1f
 
-	mov	pc, lr				@ atag pointer is ok
+2:	mov	pc, lr				@ atag/dtb pointer is ok
 
 1:	mov	r2, #0
 	mov	pc, lr
@@ -140,7 +147,7 @@ ENDPROC(__vet_atags)
  *
  *  r0  = cp#15 control register
  *  r1  = machine ID
- *  r2  = atags pointer
+ *  r2  = atags/dtb pointer
  *  r9  = processor ID
  */
 	__INIT
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index f17d9a0..65d9489 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -66,7 +66,7 @@
  *
  * This is normally called from the decompressor code.  The requirements
  * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
- * r1 = machine nr, r2 = atags pointer.
+ * r1 = machine nr, r2 = atags or dtb pointer.
  *
  * This code is mostly position independent, so if you link the kernel at
  * 0xc0008000, you call this at __pa(0xc0008000).
@@ -93,7 +93,7 @@ ENTRY(stext)
 	beq	__error_a			@ yes, error 'a'
 
 	/*
-	 * r1 = machine no, r2 = atags,
+	 * r1 = machine no, r2 = atags or dtb,
 	 * r8 = machinfo, r9 = cpuid, r10 = procinfo
 	 */
 	bl	__vet_atags
@@ -335,7 +335,7 @@ __secondary_data:
  *
  *  r0  = cp#15 control register
  *  r1  = machine ID
- *  r2  = atags pointer
+ *  r2  = atags or dtb pointer
  *  r4  = page table pointer
  *  r9  = processor ID
  *  r13 = *virtual* address to jump to upon completion
@@ -372,7 +372,7 @@ ENDPROC(__enable_mmu)
  *
  *  r0  = cp#15 control register
  *  r1  = machine ID
- *  r2  = atags pointer
+ *  r2  = atags or dtb pointer
  *  r9  = processor ID
  *  r13 = *virtual* address to jump to upon completion
  *


  reply	other threads:[~2011-01-18 20:29 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-18 20:28 [PATCH 0/8] Basic ARM device tree support Grant Likely
2011-01-18 20:29 ` Grant Likely [this message]
2011-01-18 21:26   ` [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image Nicolas Pitre
2011-01-18 21:42     ` Grant Likely
2011-01-18 20:29 ` [PATCH 2/8] arm/dt: allow bootmem reservation for device tree blob and initrd Grant Likely
2011-01-18 20:29 ` [PATCH 3/8] arm/dt: Allow CONFIG_OF on ARM Grant Likely
2011-01-18 20:29 ` [PATCH 4/8] arm/dt: consolidate atags setup into setup_machine_atags Grant Likely
2011-01-18 20:29 ` [PATCH 5/8] arm/dt: probe for platforms via the device tree Grant Likely
2011-01-18 20:29 ` [PATCH 6/8] arm/dt: Basic versatile devicetree support Grant Likely
2011-01-18 20:29 ` [PATCH 7/8] arm/tegra: Fix tegra irq_data conversion Grant Likely
2011-01-18 20:29 ` [PATCH 8/8] arm/dt: Basic tegra devicetree support Grant Likely
2011-01-18 21:47   ` Nicolas Pitre
2011-01-18 21:55     ` Grant Likely
2011-01-19 12:14   ` Sergei Shtylyov
2011-01-26 20:04 ` [PATCH 0/8] Basic ARM device tree support John Linn
2011-01-26 22:32   ` Rob Herring
2011-01-28  6:37     ` Jason Liu
2011-01-31 18:05   ` Grant Likely
2011-01-31 18:06     ` John Linn

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