| Message ID | 1381748590-14279-9-git-send-email-lorenzo.pieralisi@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Oct 14, 2013 at 12:03:05PM +0100, Lorenzo Pieralisi wrote: > When a CPU is shutdown either through CPU idle or suspend to RAM, the > content of debug monitor registers must be reset or restored to proper > values when CPU resume from low power states. This patch implements a > CPU PM notifier that allows to restore the content of debug monitor > registers to allow proper suspend/resume operations. How do you deal with pstate in this series? In particular, the single-step state machine is partially driven by bits in the SPSR, so you need to be careful with preserving that (may even require a dummy exception return... not sure). > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > --- > arch/arm64/kernel/debug-monitors.c | 38 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c > index cbfacf7..28ce685 100644 > --- a/arch/arm64/kernel/debug-monitors.c > +++ b/arch/arm64/kernel/debug-monitors.c > @@ -19,6 +19,7 @@ > */ > > #include <linux/cpu.h> > +#include <linux/cpu_pm.h> > #include <linux/debugfs.h> > #include <linux/hardirq.h> > #include <linux/init.h> > @@ -154,6 +155,42 @@ static struct notifier_block os_lock_nb = { > .notifier_call = os_lock_notify, > }; > > +#ifdef CONFIG_CPU_PM > +static DEFINE_PER_CPU(u32, mdscr); > + > +static int dm_cpu_pm_notify(struct notifier_block *self, unsigned long action, > + void *v) > +{ > + switch (action) { > + case CPU_PM_ENTER: > + __get_cpu_var(mdscr) = mdscr_read(); I'm concerned about simply saving/restoring the mdscr. Both the MDE and KDE bits are ref-counted for each CPU, so we'd need to guarantee no context switching between the CPU_PM_ENTER and CPU_PM_EXIT invocations of this notifier. Is that the case? > + break; > + case CPU_PM_EXIT: > + clear_os_lock(NULL); > + mdscr_write(__get_cpu_var(mdscr)); I think you should do this the other way round. Also, back to PSTATE, you need to take care when clearing the D bit, since you definitely want to either restore or zero the mdscr first. Will
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index cbfacf7..28ce685 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -19,6 +19,7 @@ */ #include <linux/cpu.h> +#include <linux/cpu_pm.h> #include <linux/debugfs.h> #include <linux/hardirq.h> #include <linux/init.h> @@ -154,6 +155,42 @@ static struct notifier_block os_lock_nb = { .notifier_call = os_lock_notify, }; +#ifdef CONFIG_CPU_PM +static DEFINE_PER_CPU(u32, mdscr); + +static int dm_cpu_pm_notify(struct notifier_block *self, unsigned long action, + void *v) +{ + switch (action) { + case CPU_PM_ENTER: + __get_cpu_var(mdscr) = mdscr_read(); + break; + case CPU_PM_EXIT: + clear_os_lock(NULL); + mdscr_write(__get_cpu_var(mdscr)); + break; + case CPU_PM_ENTER_FAILED: + default: + return NOTIFY_DONE; + } + + return NOTIFY_OK; +} + +static struct notifier_block dm_cpu_pm_nb = { + .notifier_call = dm_cpu_pm_notify, +}; + +static void __init debug_monitors_pm_init(void) +{ + cpu_pm_register_notifier(&dm_cpu_pm_nb); +} +#else +static inline void debug_monitors_pm_init(void) +{ +} +#endif + static int debug_monitors_init(void) { /* Clear the OS lock. */ @@ -162,6 +199,7 @@ static int debug_monitors_init(void) /* Register hotplug handler. */ register_cpu_notifier(&os_lock_nb); + debug_monitors_pm_init(); return 0; } postcore_initcall(debug_monitors_init);
When a CPU is shutdown either through CPU idle or suspend to RAM, the content of debug monitor registers must be reset or restored to proper values when CPU resume from low power states. This patch implements a CPU PM notifier that allows to restore the content of debug monitor registers to allow proper suspend/resume operations. Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> --- arch/arm64/kernel/debug-monitors.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)