Re: [PATCH] powerpc: Add support for using doorbells for SMP IPI

Mon, 23 Feb 2009 08:24:57 -0800 


On Feb 22, 2009, at 8:43 PM, Benjamin Herrenschmidt wrote:


On Thu, 2009-02-12 at 17:54 -0600, Kumar Gala wrote:
The e500mc supports the new msgsnd/doorbell mechanisms that were added in the Power ISA 2.05 architecture. We use the normal level doorbell for 
doing SMP IPIs at this point.


Any reason why you don't use the tag ? I'm not too familiar with the
doorbell stuff just yet but can't you use that instead of doing those
atomics ?
tag just conveys the type of doorbell (normal, critical, etc.). So for the 4 IPI msgs we support we need software to keep track. 


On thing we also need to look at is change our low level msg send to
take a CPU mask.

This will be better generically and we need a good cpu mask based IPI
for the TLB stuff anyway. Volunteer ? :-)


yeah.. It something on the list :)

- k


Signed-off-by: Kumar Gala <ga...@kernel.crashing.org>
---
arch/powerpc/include/asm/cputable.h  |    4 ++-
arch/powerpc/include/asm/dbell.h | 43 ++++++++++++++++++++++++ +++++++++ 
arch/powerpc/kernel/Makefile         |    2 +-
arch/powerpc/kernel/dbell.c | 44 ++++++++++++++++++++++++ ++++++++++ 
arch/powerpc/kernel/head_fsl_booke.S |    6 ++++-
arch/powerpc/kernel/traps.c          |   21 ++++++++++++++++
6 files changed, 117 insertions(+), 3 deletions(-)
create mode 100644 arch/powerpc/include/asm/dbell.h
create mode 100644 arch/powerpc/kernel/dbell.c
diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/ include/asm/cputable.h 
index 4911104..fca1611 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -145,6 +145,7 @@ extern const char *powerpc_base_platform;
#define CPU_FTR_USE_TB                  ASM_CONST(0x0000000000000040)
#define CPU_FTR_L2CSR                   ASM_CONST(0x0000000000000080)
#define CPU_FTR_601                     ASM_CONST(0x0000000000000100)
+#define CPU_FTR_DBELL                  ASM_CONST(0x0000000000000200)
#define CPU_FTR_CAN_NAP                 ASM_CONST(0x0000000000000400)
#define CPU_FTR_L3CR                    ASM_CONST(0x0000000000000800)
#define CPU_FTR_L3_DISABLE_NAP          ASM_CONST(0x0000000000001000)
@@ -373,7 +374,8 @@ extern const char *powerpc_base_platform;
            CPU_FTR_NODSISRALIGN | CPU_FTR_NOEXECUTE)
#define CPU_FTRS_E500MC (CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_NODSISRALIGN | \
-           CPU_FTR_L2CSR | CPU_FTR_LWSYNC | CPU_FTR_NOEXECUTE)
+           CPU_FTR_L2CSR | CPU_FTR_LWSYNC | CPU_FTR_NOEXECUTE | \
+           CPU_FTR_DBELL)
#define CPU_FTRS_GENERIC_32     (CPU_FTR_COMMON | CPU_FTR_NODSISRALIGN)

/* 64-bit CPUs */
diff --git a/arch/powerpc/include/asm/dbell.h b/arch/powerpc/ include/asm/dbell.h 
new file mode 100644
index 0000000..501189a
--- /dev/null
+++ b/arch/powerpc/include/asm/dbell.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2009 Freescale Semicondutor, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * provides masks and opcode images for use by code generation, emulation 
+ * and for instructions that older assemblers might not know about
+ */
+#ifndef _ASM_POWERPC_DBELL_H
+#define _ASM_POWERPC_DBELL_H
+
+#include <linux/smp.h>
+#include <linux/threads.h>
+
+#include <asm/ppc-opcode.h>
+
+#define PPC_DBELL_MSG_BRDCAST  (0x04000000)
+#define PPC_DBELL_TYPE(x)      (((x) & 0xf) << 28)
+enum ppc_dbell {
+       PPC_DBELL = 0,          /* doorbell */
+       PPC_DBELL_CRIT = 1,     /* critical doorbell */
+       PPC_G_DBELL = 2,        /* guest doorbell */
+       PPC_G_DBELL_CRIT = 3,   /* guest critical doorbell */
+       PPC_G_DBELL_MC = 4,     /* guest mcheck doorbell */
+};
+
+#ifdef CONFIG_SMP
+extern unsigned long dbell_smp_message[NR_CPUS];
+extern void smp_dbell_message_pass(int target, int msg);
+#endif
+
+static inline void ppc_msgsnd(enum ppc_dbell type, u32 flags, u32 tag) 
+{
+       u32 msg = PPC_DBELL_TYPE(type) | (flags & PPC_DBELL_MSG_BRDCAST) |
+                       (tag & 0x07ffffff);
+
+       __asm__ __volatile__ (PPC_MSGSND(%0) : : "r" (msg));
+}
+
+#endif /* _ASM_POWERPC_DBELL_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/ Makefile 
index d159921..f420844 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -61,7 +61,7 @@ obj-$(CONFIG_HIBERNATION)     += swsusp.o suspend.o \
obj64-$(CONFIG_HIBERNATION)     += swsusp_asm64.o
obj-$(CONFIG_MODULES)           += module.o module_$(CONFIG_WORD_SIZE).o
obj-$(CONFIG_44x)               += cpu_setup_44x.o
-obj-$(CONFIG_FSL_BOOKE)                += cpu_setup_fsl_booke.o
+obj-$(CONFIG_FSL_BOOKE)                += cpu_setup_fsl_booke.o dbell.o

extra-$(CONFIG_PPC_STD_MMU)     := head_32.o
extra-$(CONFIG_PPC64)           := head_64.o
diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/ dbell.c 
new file mode 100644
index 0000000..1493734
--- /dev/null
+++ b/arch/powerpc/kernel/dbell.c
@@ -0,0 +1,44 @@
+/*
+ * Author: Kumar Gala <ga...@kernel.crashing.org>
+ *
+ * Copyright 2009 Freescale Semiconductor Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 of the License, or (at your 
+ * option) any later version.
+ */
+
+#include <linux/stddef.h>
+#include <linux/kernel.h>
+#include <linux/smp.h>
+#include <linux/threads.h>
+
+#include <asm/dbell.h>
+
+#ifdef CONFIG_SMP
+unsigned long dbell_smp_message[NR_CPUS];
+
+void smp_dbell_message_pass(int target, int msg)
+{
+       int i;
+
+       if(target < NR_CPUS) {
+               set_bit(msg, &dbell_smp_message[target]);
+               ppc_msgsnd(PPC_DBELL, 0, target);
+       }
+       else if(target == MSG_ALL_BUT_SELF) {
+               for_each_online_cpu(i) {
+                       if (i == smp_processor_id())
+                               continue;
+                       set_bit(msg, &dbell_smp_message[i]);
+                       ppc_msgsnd(PPC_DBELL, 0, i);
+               }
+       }
+       else { /* target == MSG_ALL */
+               for_each_online_cpu(i)
+                       set_bit(msg, &dbell_smp_message[i]);
+               ppc_msgsnd(PPC_DBELL, PPC_DBELL_MSG_BRDCAST, 0);
+       }
+}
+#endif
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/ kernel/head_fsl_booke.S 
index 4ea6e1a..4c22620 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -698,7 +698,9 @@ interrupt_base:
        /* Performance Monitor */
EXCEPTION(0x2060, PerformanceMonitor, performance_monitor_exception, EXC_XFER_STD) 

-       EXCEPTION(0x2070, Doorbell, unknown_exception, EXC_XFER_STD)
+       EXCEPTION(0x2070, Doorbell, doorbell_exception, EXC_XFER_STD)
+
+       CRITICAL_EXCEPTION(0x2080, CriticalDoorbell, unknown_exception)

        /* Debug Interrupt */
        DEBUG_DEBUG_EXCEPTION
@@ -921,6 +923,8 @@ _GLOBAL(__setup_e500mc_ivors)
        mtspr   SPRN_IVOR35,r3
        li      r3,doorb...@l
        mtspr   SPRN_IVOR36,r3
+       li      r3,criticaldoorb...@l
+       mtspr   SPRN_IVOR37,r3
        sync
        blr
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/ traps.c 
index 970d66e..678fbff 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -53,6 +53,9 @@
#endif
#include <asm/kexec.h>
#include <asm/ppc-opcode.h>
+#ifdef CONFIG_FSL_BOOKE
+#include <asm/dbell.h>
+#endif

#if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
int (*__debugger)(struct pt_regs *regs);
@@ -1122,6 +1125,24 @@ void vsx_assist_exception(struct pt_regs *regs) 
#endif /* CONFIG_VSX */

#ifdef CONFIG_FSL_BOOKE
+
+void doorbell_exception(struct pt_regs *regs)
+{
+#ifdef CONFIG_SMP
+       int cpu = smp_processor_id();
+       int msg;
+
+       if (num_online_cpus() < 2)
+               return;
+
+       for (msg = 0; msg < 4; msg++)
+               if (test_and_clear_bit(msg, &dbell_smp_message[cpu]))
+                       smp_message_recv(msg);
+#else
+       printk(KERN_WARNING "Received doorbell on non-smp system\n");
+#endif
+}
+
void CacheLockingException(struct pt_regs *regs, unsigned long address, 
                           unsigned long error_code)
{


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