ARM: multi-cluster PM: secondary kernel entry code

CPUs in cluster based systems, such as big.LITTLE, 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.

The mcpm prefix stands for "multi cluster power management", however
this is usable on single cluster systems as well.  Only the basic
structure is introduced here.  This will be extended with later patches.

In order not to complexify things more than they currently have to,
the planned work to make runtime adjusted MPIDR based indexing and
dynamic memory allocation for cluster states is postponed to a later
cycle. The MAX_NR_CLUSTERS and MAX_CPUS_PER_CLUSTER static definitions
should be sufficient for those systems expected to be available in the
near future.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 2c3bdce..2d17275 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1599,6 +1599,14 @@ config HAVE_ARM_TWD
        help
          This options enables support for the ARM timer and watchdog unit
 
+config MCPM
+       bool "Multi-Cluster Power Management"
+       depends on CPU_V7 && SMP
+       help
+         This option provides the common power management infrastructure
+         for (multi-)cluster based systems, such as big.LITTLE based
+         systems.
+
 choice
        prompt "Memory split"
        default VMSPLIT_3G

diff --git a/arch/arm/common/Makefile b/arch/arm/common/Makefile
index dc8dd0d..b070671 100644 (file)
--- a/arch/arm/common/Makefile
+++ b/arch/arm/common/Makefile
@@ -11,3 +11,4 @@ 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_MCPM)             += mcpm_head.o mcpm_entry.o

diff --git a/arch/arm/common/mcpm_entry.c b/arch/arm/common/mcpm_entry.c
new file mode 100644 (file)
index 0000000..7cbf700
--- /dev/null
+++ b/arch/arm/common/mcpm_entry.c
@@ -0,0 +1,22 @@
+/*
+ * arch/arm/common/mcpm_entry.c -- entry point for multi-cluster PM
+ *
+ * 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 <asm/mcpm.h>
+#include <asm/cacheflush.h>
+
+extern unsigned long mcpm_entry_vectors[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
+
+void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr)
+{
+       unsigned long val = ptr ? virt_to_phys(ptr) : 0;
+       mcpm_entry_vectors[cluster][cpu] = val;
+       sync_cache_w(&mcpm_entry_vectors[cluster][cpu]);
+}

diff --git a/arch/arm/common/mcpm_head.S b/arch/arm/common/mcpm_head.S
new file mode 100644 (file)
index 0000000..68c9903
--- /dev/null
+++ b/arch/arm/common/mcpm_head.S
@@ -0,0 +1,86 @@
+/*
+ * arch/arm/common/mcpm_head.S -- kernel entry point for multi-cluster PM
+ *
+ * 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/mcpm.h>
+
+       .macro  pr_dbg  string
+#if defined(CONFIG_DEBUG_LL) && defined(DEBUG)
+       b       1901f
+1902:  .asciz  "CPU"
+1903:  .asciz  " cluster"
+1904:  .asciz  ": \string"
+       .align
+1901:  adr     r0, 1902b
+       bl      printascii
+       mov     r0, r9
+       bl      printhex8
+       adr     r0, 1903b
+       bl      printascii
+       mov     r0, r10
+       bl      printhex8
+       adr     r0, 1904b
+       bl      printascii
+#endif
+       .endm
+
+       .arm
+       .align
+
+ENTRY(mcpm_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, #8                  @ r9 = cpu
+       ubfx    r10, r0, #8, #8                 @ r10 = cluster
+       mov     r3, #MAX_CPUS_PER_CLUSTER
+       mla     r4, r3, r10, r9                 @ r4 = canonical CPU index
+       cmp     r4, #(MAX_CPUS_PER_CLUSTER * MAX_NR_CLUSTERS)
+       blo     2f
+
+       /* We didn't expect this CPU.  Try to cheaply make it quiet. */
+1:     wfi
+       wfe
+       b       1b
+
+2:     pr_dbg  "kernel mcpm_entry_point\n"
+
+       /*
+        * MMU is off so we need to get to mcpm_entry_vectors in a
+        * position independent way.
+        */
+       adr     r5, 3f
+       ldr     r6, [r5]
+       add     r6, r5, r6                      @ r6 = mcpm_entry_vectors
+
+mcpm_entry_gated:
+       ldr     r5, [r6, r4, lsl #2]            @ r5 = CPU entry vector
+       cmp     r5, #0
+       wfeeq
+       beq     mcpm_entry_gated
+       pr_dbg  "released\n"
+       bx      r5
+
+       .align  2
+
+3:     .word   mcpm_entry_vectors - .
+
+ENDPROC(mcpm_entry_point)
+
+       .bss
+       .align  5
+
+       .type   mcpm_entry_vectors, #object
+ENTRY(mcpm_entry_vectors)
+       .space  4 * MAX_NR_CLUSTERS * MAX_CPUS_PER_CLUSTER

diff --git a/arch/arm/include/asm/mcpm.h b/arch/arm/include/asm/mcpm.h
new file mode 100644 (file)
index 0000000..470a417
--- /dev/null
+++ b/arch/arm/include/asm/mcpm.h
@@ -0,0 +1,42 @@
+/*
+ * arch/arm/include/asm/mcpm.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 MCPM_H
+#define MCPM_H
+
+/*
+ * Maximum number of possible clusters / CPUs per cluster.
+ *
+ * This should be sufficient for quite a while, while keeping the
+ * (assembly) code simpler.  When this starts to grow then we'll have
+ * to consider dynamic allocation.
+ */
+#define MAX_CPUS_PER_CLUSTER   4
+#define MAX_NR_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 mcpm_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 mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr);
+
+#endif /* ! __ASSEMBLY__ */
+#endif