[PATCH 0/3] hw_breakpoint updates for 3.9

[PATCH 0/3] hw_breakpoint updates for 3.9

[Will Deacon]

Hello,

I have a small handful of hw_breakpoint updates, all from Dietmar, that
I plan to send via Russell for 3.9.

Any comments, please shout.

Will


Dietmar Eggemann (3):
  ARM: coresight: common definition for (OS) Lock Access Register key
    value
  ARM: hw_breakpoint: Check function for OS Save and Restore mechanism
  ARM: hw_breakpoint: Debug powerdown support for self-hosted debug

 arch/arm/include/asm/cti.h                | 10 ++---
 arch/arm/include/asm/hardware/coresight.h |  6 +--
 arch/arm/include/asm/hw_breakpoint.h      |  3 ++
 arch/arm/kernel/hw_breakpoint.c           | 61 +++++++++++++++++++++++++++----
 4 files changed, 62 insertions(+), 18 deletions(-)

-- 
1.8.0

[PATCH 1/3] ARM: coresight: common definition for (OS) Lock Access Register key value

[Will Deacon]

From: Dietmar Eggemann <dietmar.eggemann@arm.com>

Coresight components and debug are using a common lock control mechansim.
Writing 0xC5ACCE55 to the Lock Access Register (LAR) in case of a coresight
components enables further access to the coresight device registers. Writing
any other value to it removes the write access.
Writing 0xC5ACCE55 to the OS Lock Access Register (OSLAR) in case of debug
locks the debug register for further access to the debug registers. Writing
any other value to it unlocks the debug registers.

Unfortunately, the existing coresight code uses the terms lock and unlock the
other way around. Unlocking stands for enabling write access and locking for
removing write access.

That is why the definition of the LAR and OSLAR key value has been changed to
CS_LAR_KEY.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm/include/asm/cti.h                | 10 +++-------
 arch/arm/include/asm/hardware/coresight.h |  6 +++---
 arch/arm/kernel/hw_breakpoint.c           |  5 +++--
 3 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/arm/include/asm/cti.h b/arch/arm/include/asm/cti.h
index f2e5cad..2381199 100644
--- a/arch/arm/include/asm/cti.h
+++ b/arch/arm/include/asm/cti.h
@@ -2,6 +2,7 @@
 #define __ASMARM_CTI_H
 
 #include	<asm/io.h>
+#include	<asm/hardware/coresight.h>
 
 /* The registers' definition is from section 3.2 of
  * Embedded Cross Trigger Revision: r0p0
@@ -35,11 +36,6 @@
 #define		LOCKACCESS		0xFB0
 #define		LOCKSTATUS		0xFB4
 
-/* write this value to LOCKACCESS will unlock the module, and
- * other value will lock the module
- */
-#define		LOCKCODE		0xC5ACCE55
-
 /**
  * struct cti - cross trigger interface struct
  * @base: mapped virtual address for the cti base
@@ -146,7 +142,7 @@ static inline void cti_irq_ack(struct cti *cti)
  */
 static inline void cti_unlock(struct cti *cti)
 {
-	__raw_writel(LOCKCODE, cti->base + LOCKACCESS);
+	__raw_writel(CS_LAR_KEY, cti->base + LOCKACCESS);
 }
 
 /**
@@ -158,6 +154,6 @@ static inline void cti_unlock(struct cti *cti)
  */
 static inline void cti_lock(struct cti *cti)
 {
-	__raw_writel(~LOCKCODE, cti->base + LOCKACCESS);
+	__raw_writel(~CS_LAR_KEY, cti->base + LOCKACCESS);
 }
 #endif
diff --git a/arch/arm/include/asm/hardware/coresight.h b/arch/arm/include/asm/hardware/coresight.h
index 7ecd793..0cf7a6b 100644
--- a/arch/arm/include/asm/hardware/coresight.h
+++ b/arch/arm/include/asm/hardware/coresight.h
@@ -36,7 +36,7 @@
 /* CoreSight Component Registers */
 #define CSCR_CLASS	0xff4
 
-#define UNLOCK_MAGIC	0xc5acce55
+#define CS_LAR_KEY	0xc5acce55
 
 /* ETM control register, "ETM Architecture", 3.3.1 */
 #define ETMR_CTRL		0
@@ -147,11 +147,11 @@
 
 #define etm_lock(t) do { etm_writel((t), 0, CSMR_LOCKACCESS); } while (0)
 #define etm_unlock(t) \
-	do { etm_writel((t), UNLOCK_MAGIC, CSMR_LOCKACCESS); } while (0)
+	do { etm_writel((t), CS_LAR_KEY, CSMR_LOCKACCESS); } while (0)
 
 #define etb_lock(t) do { etb_writel((t), 0, CSMR_LOCKACCESS); } while (0)
 #define etb_unlock(t) \
-	do { etb_writel((t), UNLOCK_MAGIC, CSMR_LOCKACCESS); } while (0)
+	do { etb_writel((t), CS_LAR_KEY, CSMR_LOCKACCESS); } while (0)
 
 #endif /* __ASM_HARDWARE_CORESIGHT_H */
 
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 5ff2e77..34e9375 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -35,6 +35,7 @@
 #include <asm/hw_breakpoint.h>
 #include <asm/kdebug.h>
 #include <asm/traps.h>
+#include <asm/hardware/coresight.h>
 
 /* Breakpoint currently in use for each BRP. */
 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
@@ -955,9 +956,9 @@ static void reset_ctrl_regs(void *unused)
 
 	/*
 	 * Unconditionally clear the OS lock by writing a value
-	 * other than 0xC5ACCE55 to the access register.
+	 * other than CS_LAR_KEY to the access register.
 	 */
-	ARM_DBG_WRITE(c1, c0, 4, 0);
+	ARM_DBG_WRITE(c1, c0, 4, ~CS_LAR_KEY);
 	isb();
 
 	/*
-- 
1.8.0

[PATCH 2/3] ARM: hw_breakpoint: Check function for OS Save and Restore mechanism

[Will Deacon]

From: Dietmar Eggemann <dietmar.eggemann@arm.com>

v7 debug introduced OS Save and Restore mechanism. On a v7 debug SinglePower
system, i.e a system without a separate core and debug power domain, which does
not support external debug over powerdown, it is implementation defined whether
OS Save and Restore is implemented.
v7.1 debug requires OS Save and Restore mechanism. v6 debug and v6.1 debug do
not implement it.

A new global variable bool has_ossr is introduced and is determined in
arch_hw_breakpoint_init() like debug_arch or the number of BRPs/WRPs.

The logic how to check if OS Save and Restore is supported has changed with
this patch. In reset_ctrl_regs() a mask consisting of OSLM[1] (OSLSR.3) and
OSLM[0] (OSLSR.0) was used to check if the system supports OS Save and
Restore. In the new function core_has_os_save_restore() only OSLM[0] is used.
It is not necessary to check OSLM[1] too since it is v7.1 debug specific and
v7.1 debug requires OS Save and Restore and thus OS Lock.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm/include/asm/hw_breakpoint.h |  3 +++
 arch/arm/kernel/hw_breakpoint.c      | 28 +++++++++++++++++++++++-----
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/arch/arm/include/asm/hw_breakpoint.h b/arch/arm/include/asm/hw_breakpoint.h
index 01169dd..eef55ea 100644
--- a/arch/arm/include/asm/hw_breakpoint.h
+++ b/arch/arm/include/asm/hw_breakpoint.h
@@ -85,6 +85,9 @@ static inline void decode_ctrl_reg(u32 reg,
 #define ARM_DSCR_HDBGEN		(1 << 14)
 #define ARM_DSCR_MDBGEN		(1 << 15)
 
+/* OSLSR os lock model bits */
+#define ARM_OSLSR_OSLM0		(1 << 0)
+
 /* opcode2 numbers for the co-processor instructions. */
 #define ARM_OP2_BVR		4
 #define ARM_OP2_BCR		5
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 34e9375..201d440 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -50,6 +50,9 @@ static int core_num_wrps;
 /* Debug architecture version. */
 static u8 debug_arch;
 
+/* Does debug architecture support OS Save and Restore? */
+static bool has_ossr;
+
 /* Maximum supported watchpoint length. */
 static u8 max_watchpoint_len;
 
@@ -904,6 +907,23 @@ static struct undef_hook debug_reg_hook = {
 	.fn		= debug_reg_trap,
 };
 
+/* Does this core support OS Save and Restore? */
+static bool core_has_os_save_restore(void)
+{
+	u32 oslsr;
+
+	switch (get_debug_arch()) {
+	case ARM_DEBUG_ARCH_V7_1:
+		return true;
+	case ARM_DEBUG_ARCH_V7_ECP14:
+		ARM_DBG_READ(c1, c1, 4, oslsr);
+		if (oslsr & ARM_OSLSR_OSLM0)
+			return true;
+	default:
+		return false;
+	}
+}
+
 static void reset_ctrl_regs(void *unused)
 {
 	int i, raw_num_brps, err = 0, cpu = smp_processor_id();
@@ -931,11 +951,7 @@ static void reset_ctrl_regs(void *unused)
 		if ((val & 0x1) == 0)
 			err = -EPERM;
 
-		/*
-		 * Check whether we implement OS save and restore.
-		 */
-		ARM_DBG_READ(c1, c1, 4, val);
-		if ((val & 0x9) == 0)
+		if (!has_ossr)
 			goto clear_vcr;
 		break;
 	case ARM_DEBUG_ARCH_V7_1:
@@ -1025,6 +1041,8 @@ static int __init arch_hw_breakpoint_init(void)
 		return 0;
 	}
 
+	has_ossr = core_has_os_save_restore();
+
 	/* Determine how many BRPs/WRPs are available. */
 	core_num_brps = get_num_brps();
 	core_num_wrps = get_num_wrps();
-- 
1.8.0

[PATCH 3/3] ARM: hw_breakpoint: Debug powerdown support for self-hosted debug

[Will Deacon]

From: Dietmar Eggemann <dietmar.eggemann@arm.com>

This patch introduces debug powerdown support for self-hosted debug for v7
and v7.1 debug architecture for a SinglePower system, i.e. a system without a
separate core and debug power domain. On a SinglePower system the OS Lock is
lost over a powerdown.

If CONFIG_CPU_PM is set the new function pm_init() registers hw_breakpoint
with CPU PM for a system supporting OS Save and Restore.

Receiving a CPU PM EXIT notifier indicates that a single CPU has exited a low
power state. A call to reset_ctrl_regs() is hooked into the CPU PM EXIT
notifier chain. This function makes sure that the sticky power-down is clear
(only v7 debug), the OS Double Lock is clear (only v7.1 debug) and it clears
the OS Lock for v7 debug (for a system supporting OS Save and Restore) and
v7.1 debug. Furthermore, it clears any vector-catch events and all
breakpoint/watchpoint control/value registers for v7 and v7.1 debug.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
[will: removed redundant has_ossr check]
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm/kernel/hw_breakpoint.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 201d440..5eae53e 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -28,6 +28,7 @@
 #include <linux/perf_event.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/smp.h>
+#include <linux/cpu_pm.h>
 
 #include <asm/cacheflush.h>
 #include <asm/cputype.h>
@@ -1032,6 +1033,30 @@ static struct notifier_block __cpuinitdata dbg_reset_nb = {
 	.notifier_call = dbg_reset_notify,
 };
 
+#ifdef CONFIG_CPU_PM
+static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action,
+			     void *v)
+{
+	if (action == CPU_PM_EXIT)
+		reset_ctrl_regs(NULL);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata dbg_cpu_pm_nb = {
+	.notifier_call = dbg_cpu_pm_notify,
+};
+
+static void __init pm_init(void)
+{
+	cpu_pm_register_notifier(&dbg_cpu_pm_nb);
+}
+#else
+static inline void pm_init(void)
+{
+}
+#endif
+
 static int __init arch_hw_breakpoint_init(void)
 {
 	debug_arch = get_debug_arch();
@@ -1081,8 +1106,9 @@ static int __init arch_hw_breakpoint_init(void)
 	hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
 			TRAP_HWBKPT, "breakpoint debug exception");
 
-	/* Register hotplug notifier. */
+	/* Register hotplug and PM notifiers. */
 	register_cpu_notifier(&dbg_reset_nb);
+	pm_init();
 	return 0;
 }
 arch_initcall(arch_hw_breakpoint_init);
-- 
1.8.0