[PATCH v1 12/20] ARC: [plat-eznps] Use dedicated user stack top
From: Noam Camus
Date: Sat Oct 31 2015 - 09:21:13 EST
From: Noam Camus <noamc@xxxxxxxxxx>
NPS use special mapping right below TASK_SIZE.
Hence we need to lower STACK_TOP so that user stack won't
overlap NPS special mapping.
Signed-off-by: Noam Camus <noamc@xxxxxxxxxx>
Acked-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
arch/arc/include/asm/processor.h | 17 +++++++++++++++++
arch/arc/mm/tlb.c | 6 ++++++
2 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
index a603301..7266ede 100644
@@ -126,7 +126,24 @@ extern unsigned int get_wchan(struct task_struct *p);
#define USER_KERNEL_GUTTER (VMALLOC_START - TASK_SIZE)
+/* NPS architecture defines special window of 129M in user address space for
+ * special memory areas, when accessing this window the MMU do not use TLB.
+ * Instead MMU direct the access to:
+ * 0x57f00000:0x57ffffff -- 1M of closely coupled memory (aka CMEM)
+ * 0x58000000:0x5fffffff -- 16 huge pages, 8M each, with fixed map (aka FMTs)
+ * CMEM - is the fastest memory we got and its size is 16K.
+ * FMT - is used to map either to internal/external memory.
+ * Internal memory is the second fast memory and its size is 16M
+ * External memory is the biggest memory (16G) and also the slowest.
+ * STACK_TOP need to be PMD align (21bit) that is why we supply 0x57e00000.
+#define STACK_TOP 0x57e00000
+#else /* CONFIG_ARC_PLAT_EZNPS */
#define STACK_TOP TASK_SIZE
+#endif /* CONFIG_ARC_PLAT_EZNPS */
#define STACK_TOP_MAX STACK_TOP
/* This decides where the kernel will search for a free chunk of vm
diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c
index 0c75a27..306ee4c 100644
@@ -820,6 +820,12 @@ void arc_mmu_init(void)
BUILD_BUG_ON(!IS_ALIGNED((CONFIG_ARC_VMALLOC_SIZE << 20), PMD_SIZE));
+ * stack top size sanity check,
+ * Can't be done in processor.h due to header include depenedencies
+ BUILD_BUG_ON(!IS_ALIGNED(STACK_TOP, PMD_SIZE));
/* For efficiency sake, kernel is compile time built for a MMU ver
* This must match the hardware it is running on.
* Linux built for MMU V2, if run on MMU V1 will break down because V1
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