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[PATCH v2 11/25] powerpc/8xx: map 16M RAM at startup

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  [PATCH v2 11/25] powerpc/8xx: map 16M RAM at startup Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 19:00 +0200
    Re: [PATCH v2 11/25] powerpc/8xx: map 16M RAM at startup Scott Wood <scottwood@freescale.com> - 2015-09-29 02:00 +0200

#1230498 — [PATCH v2 11/25] powerpc/8xx: map 16M RAM at startup

On recent kernels, with some debug options like for instance
CONFIG_LOCKDEP, the BSS requires more than 8M memory, allthough
the kernel code fits in the first 8M.
Today, it is necessary to activate CONFIG_PIN_TLB to get more than 8M
at startup, allthough pinning TLB is not necessary for that.

This patch adds a second 8M page to the initial mapping in order to
have 16M mapped regardless of CONFIG_PIN_TLB, like several other
32 bits PPC (40x, 601, ...)

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
No change in v2

 arch/powerpc/kernel/head_8xx.S | 2 ++
 arch/powerpc/mm/8xx_mmu.c      | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 41b5d1b..1238fbe 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -871,6 +871,7 @@ initial_mmu:
 	*/
 	addi	r10, r10, 0x0100
 	mtspr	SPRN_MD_CTR, r10
+#endif
 
 	lis	r8, KERNELBASE@h	/* Create vaddr for TLB */
 	addis	r8, r8, 0x0080		/* Add 8M */
@@ -883,6 +884,7 @@ initial_mmu:
 	addis	r11, r11, 0x0080	/* Add 8M */
 	mtspr	SPRN_MD_RPN, r11
 
+#ifdef CONFIG_PIN_TLB
 	addi	r10, r10, 0x0100
 	mtspr	SPRN_MD_CTR, r10
 
diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c
index eeca14b..28283e2 100644
--- a/arch/powerpc/mm/8xx_mmu.c
+++ b/arch/powerpc/mm/8xx_mmu.c
@@ -144,7 +144,7 @@ void setup_initial_memory_limit(phys_addr_t first_memblock_base,
 	/* 8xx can only access 24MB at the moment */
 	memblock_set_current_limit(min_t(u64, first_memblock_size, 0x01800000));
 #else
-	/* 8xx can only access 8MB at the moment */
-	memblock_set_current_limit(min_t(u64, first_memblock_size, 0x00800000));
+	/* 8xx can only access 16MB at the moment */
+	memblock_set_current_limit(min_t(u64, first_memblock_size, 0x01000000));
 #endif
 }
-- 
2.1.0

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#1234580

On Tue, Sep 22, 2015 at 06:50:50PM +0200, Christophe Leroy wrote:
> On recent kernels, with some debug options like for instance
> CONFIG_LOCKDEP, the BSS requires more than 8M memory, allthough
> the kernel code fits in the first 8M.
> Today, it is necessary to activate CONFIG_PIN_TLB to get more than 8M
> at startup, allthough pinning TLB is not necessary for that.
> 
> This patch adds a second 8M page to the initial mapping in order to
> have 16M mapped regardless of CONFIG_PIN_TLB, like several other
> 32 bits PPC (40x, 601, ...)
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---

Is the assumption that nobody is still running 8xx systems with only 8
MiB RAM on current kernels?

-Scott
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