[PATCH v2 02/16] ARM: b.L: secondary kernel entry code
Nicolas Pitre
nicolas.pitre at linaro.org
Thu Jan 24 01:27:45 EST 2013
CPUs in a big.LITTLE systems have special needs when entering the kernel
due to a hotplug event, or when resuming from a deep sleep mode.
This is vectorized so multiple CPUs can enter the kernel in parallel
without serialization.
Only the basic structure is introduced here. This will be extended
later.
TODO: MPIDR based indexing should eventually be made runtime adjusted.
Signed-off-by: Nicolas Pitre <nico at linaro.org>
---
arch/arm/Kconfig | 6 +++
arch/arm/common/Makefile | 1 +
arch/arm/common/bL_entry.c | 29 +++++++++++++++
arch/arm/common/bL_head.S | 81 +++++++++++++++++++++++++++++++++++++++++
arch/arm/include/asm/bL_entry.h | 35 ++++++++++++++++++
5 files changed, 152 insertions(+)
create mode 100644 arch/arm/common/bL_entry.c
create mode 100644 arch/arm/common/bL_head.S
create mode 100644 arch/arm/include/asm/bL_entry.h
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 67874b82a4..3dd5591c79 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1584,6 +1584,12 @@ config HAVE_ARM_TWD
help
This options enables support for the ARM timer and watchdog unit
+config BIG_LITTLE
+ bool "big.LITTLE support"
+ depends on CPU_V7 && SMP
+ help
+ This option enables support for the big.LITTLE architecture.
+
choice
prompt "Memory split"
default VMSPLIT_3G
diff --git a/arch/arm/common/Makefile b/arch/arm/common/Makefile
index e8a4e58f1b..8025899a20 100644
--- a/arch/arm/common/Makefile
+++ b/arch/arm/common/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_SHARP_PARAM) += sharpsl_param.o
obj-$(CONFIG_SHARP_SCOOP) += scoop.o
obj-$(CONFIG_PCI_HOST_ITE8152) += it8152.o
obj-$(CONFIG_ARM_TIMER_SP804) += timer-sp.o
+obj-$(CONFIG_BIG_LITTLE) += bL_head.o bL_entry.o
diff --git a/arch/arm/common/bL_entry.c b/arch/arm/common/bL_entry.c
new file mode 100644
index 0000000000..4e1044612d
--- /dev/null
+++ b/arch/arm/common/bL_entry.c
@@ -0,0 +1,29 @@
+/*
+ * arch/arm/common/bL_entry.c -- big.LITTLE kernel re-entry point
+ *
+ * Created by: Nicolas Pitre, March 2012
+ * Copyright: (C) 2012-2013 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+#include <asm/bL_entry.h>
+#include <asm/barrier.h>
+#include <asm/proc-fns.h>
+#include <asm/cacheflush.h>
+
+extern volatile unsigned long bL_entry_vectors[BL_MAX_CLUSTERS][BL_MAX_CPUS_PER_CLUSTER];
+
+void bL_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr)
+{
+ unsigned long val = ptr ? virt_to_phys(ptr) : 0;
+ bL_entry_vectors[cluster][cpu] = val;
+ __cpuc_flush_dcache_area((void *)&bL_entry_vectors[cluster][cpu], 4);
+ outer_clean_range(__pa(&bL_entry_vectors[cluster][cpu]),
+ __pa(&bL_entry_vectors[cluster][cpu + 1]));
+}
diff --git a/arch/arm/common/bL_head.S b/arch/arm/common/bL_head.S
new file mode 100644
index 0000000000..072a13da20
--- /dev/null
+++ b/arch/arm/common/bL_head.S
@@ -0,0 +1,81 @@
+/*
+ * arch/arm/common/bL_head.S -- big.LITTLE kernel re-entry point
+ *
+ * Created by: Nicolas Pitre, March 2012
+ * Copyright: (C) 2012-2013 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/linkage.h>
+#include <asm/bL_entry.h>
+
+ .macro pr_dbg cpu, string
+#if defined(CONFIG_DEBUG_LL) && defined(DEBUG)
+ b 1901f
+1902: .ascii "CPU 0: \0CPU 1: \0CPU 2: \0CPU 3: \0"
+ .ascii "CPU 4: \0CPU 5: \0CPU 6: \0CPU 7: \0"
+1903: .asciz "\string"
+ .align
+1901: adr r0, 1902b
+ add r0, r0, \cpu, lsl #3
+ bl printascii
+ adr r0, 1903b
+ bl printascii
+#endif
+ .endm
+
+ .arm
+ .align
+
+ENTRY(bL_entry_point)
+
+ THUMB( adr r12, BSYM(1f) )
+ THUMB( bx r12 )
+ THUMB( .thumb )
+1:
+ mrc p15, 0, r0, c0, c0, 5 @ MPIDR
+ ubfx r9, r0, #0, #4 @ r9 = cpu
+ ubfx r10, r0, #8, #4 @ r10 = cluster
+ mov r3, #BL_MAX_CPUS_PER_CLUSTER
+ mla r4, r3, r10, r9 @ r4 = canonical CPU index
+ cmp r4, #(BL_MAX_CPUS_PER_CLUSTER * BL_MAX_CLUSTERS)
+ blo 2f
+
+ /* We didn't expect this CPU. Try to cheaply make it quiet. */
+1: wfi
+ wfe
+ b 1b
+
+2: pr_dbg r4, "kernel bL_entry_point\n"
+
+ /*
+ * MMU is off so we need to get to bL_entry_vectors in a
+ * position independent way.
+ */
+ adr r5, 3f
+ ldr r6, [r5]
+ add r6, r5, r6 @ r6 = bL_entry_vectors
+
+bL_entry_gated:
+ ldr r5, [r6, r4, lsl #2] @ r5 = CPU entry vector
+ cmp r5, #0
+ wfeeq
+ beq bL_entry_gated
+ pr_dbg r4, "released\n"
+ bx r5
+
+ .align 2
+
+3: .word bL_entry_vectors - .
+
+ENDPROC(bL_entry_point)
+
+ .bss
+ .align 5
+
+ .type bL_entry_vectors, #object
+ENTRY(bL_entry_vectors)
+ .space 4 * BL_MAX_CLUSTERS * BL_MAX_CPUS_PER_CLUSTER
diff --git a/arch/arm/include/asm/bL_entry.h b/arch/arm/include/asm/bL_entry.h
new file mode 100644
index 0000000000..7525614243
--- /dev/null
+++ b/arch/arm/include/asm/bL_entry.h
@@ -0,0 +1,35 @@
+/*
+ * arch/arm/include/asm/bL_entry.h
+ *
+ * Created by: Nicolas Pitre, April 2012
+ * Copyright: (C) 2012-2013 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef BL_ENTRY_H
+#define BL_ENTRY_H
+
+#define BL_MAX_CPUS_PER_CLUSTER 4
+#define BL_MAX_CLUSTERS 2
+
+#ifndef __ASSEMBLY__
+
+/*
+ * Platform specific code should use this symbol to set up secondary
+ * entry location for processors to use when released from reset.
+ */
+extern void bL_entry_point(void);
+
+/*
+ * This is used to indicate where the given CPU from given cluster should
+ * branch once it is ready to re-enter the kernel using ptr, or NULL if it
+ * should be gated. A gated CPU is held in a WFE loop until its vector
+ * becomes non NULL.
+ */
+void bL_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr);
+
+#endif /* ! __ASSEMBLY__ */
+#endif
--
1.8.0
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