This patchset updates OS Save and Restore mechanism for v7 and v7.1 debug for self-hosted debug powerdown support to Linux 3.8-rc2.
v7 debug for self-hosted debug tested on Pandaboard (A9) which unfortunately does not support OS Save and Restore.
v7.1 debug for self-hosted debug tested on TC2 big.LITTLE testchip (cpuidle, on both A7 and A15 clusters).
Gdb (version 7.5.50.20121105-cvs) was used as the self-hosted debugger.
This patchset is against commit e01b52e 'Merge branch 'next-armlt-arm64' into integration-next' on linaro_landing_team/integration-next .
It replaces the patch 'ARM: hw_breakpoint: v7.1 self-hosted debug powerdown support'.
Dietmar Eggemann (2): 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/hw_breakpoint.h | 3 ++ arch/arm/kernel/hw_breakpoint.c | 56 +++++++++++++++++++++++++++++++--- 2 files changed, 54 insertions(+), 5 deletions(-)
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 5ff2e77..28f3c62 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -49,6 +49,9 @@ 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;
@@ -903,6 +906,23 @@ 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(); @@ -930,11 +950,7 @@ 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: @@ -1024,6 +1040,8 @@ 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();
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 Signed-off-by: Will Deacon will.deacon@arm.com --- arch/arm/kernel/hw_breakpoint.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 28f3c62..f031a4f 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> @@ -1031,6 +1032,31 @@ 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) +{ + if (has_ossr) + 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(); @@ -1082,6 +1108,8 @@ static int __init arch_hw_breakpoint_init(void)
/* Register hotplug notifier. */ register_cpu_notifier(&dbg_reset_nb); + + pm_init(); return 0; } arch_initcall(arch_hw_breakpoint_init);
-
Dietmar Eggemann