[PATCH 1/3] Implement arch disable/enable irq hooks.

These hooks ensure that a decrementer interrupt is not pending when
suspending; otherwise, problems may occur.  For example, with deep sleep
on the 831x, a pending decrementer will cause a system freeze because the
SoC thinks the decrementer interrupt would have woken the system, but the
core must have interrupts disabled due to the setup required for deep
sleep.

Signed-off-by: Scott Wood <redacted>
---
 arch/powerpc/kernel/time.c    |   41 +++++++++++++++++++++++++++++++++++++++++
 include/asm-powerpc/machdep.h |   13 +++++++++++++
 2 files changed, 54 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index b5944d8..bf7c4d3 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c

@@ -728,6 +728,47 @@ void wakeup_decrementer(void)
 	set_dec(ticks);
 }
 
+#ifdef CONFIG_SUSPEND
+void generic_suspend_disable_irqs(void)
+{
+	preempt_disable();
+
+	/* Disable the decrementer, so that it doesn't interfere
+	 * with suspending.
+	 */
+
+	set_dec(0x7fffffff);
+	local_irq_disable();
+	set_dec(0x7fffffff);
+}
+
+void generic_suspend_enable_irqs(void)
+{
+	wakeup_decrementer();
+
+	local_irq_enable();
+	preempt_enable();
+}
+
+/* Overrides the weak version in kernel/power/main.c */
+void arch_suspend_disable_irqs(void)
+{
+	if (ppc_md.suspend_disable_irqs)
+		ppc_md.suspend_disable_irqs();
+	else
+		generic_suspend_disable_irqs();
+}
+
+/* Overrides the weak version in kernel/power/main.c */
+void arch_suspend_enable_irqs(void)
+{
+	if (ppc_md.suspend_enable_irqs)
+		ppc_md.suspend_enable_irqs();
+	else
+		generic_suspend_enable_irqs();
+}
+#endif
+
 #ifdef CONFIG_SMP
 void __init smp_space_timers(unsigned int max_cpus)
 {

diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/machdep.h
index 71c6e7e..7d6d2cb 100644
--- a/include/asm-powerpc/machdep.h
+++ b/include/asm-powerpc/machdep.h

@@ -253,6 +253,16 @@ struct machdep_calls {
 	 */
 	void (*machine_kexec)(struct kimage *image);
 #endif /* CONFIG_KEXEC */
+
+#ifdef CONFIG_SUSPEND
+	/* These are called to disable and enable, respectively, IRQs when
+	 * entering a suspend state.  If NULL, then the generic versions
+	 * will be called.  The generic versions disable/enable the
+	 * decrementer along with interrupts.
+	 */
+	void (*suspend_disable_irqs)(void);
+	void (*suspend_enable_irqs)(void);
+#endif
 };
 
 extern void power4_idle(void);

@@ -326,5 +336,8 @@ static inline void log_error(char *buf, unsigned int err_type, int fatal)
 		ppc_md.log_error(buf, err_type, fatal);
 }
 
+void generic_suspend_disable_irqs(void);
+void generic_suspend_enable_irqs(void);
+
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_MACHDEP_H */

-- 
1.5.3

Scott Wood writes:

These hooks ensure that a decrementer interrupt is not pending when
suspending; otherwise, problems may occur.  For example, with deep sleep
on the 831x, a pending decrementer will cause a system freeze because the
SoC thinks the decrementer interrupt would have woken the system, but the
core must have interrupts disabled due to the setup required for deep
sleep.

+	set_dec(0x7fffffff);
+	local_irq_disable();
+	set_dec(0x7fffffff);

It might be better to use hard_irq_disable rather than
local_irq_disable here, since I think we will need that on 64-bit (and
on 32-bit if we ever do lazy irq disabling there).

+/* Overrides the weak version in kernel/power/main.c */
+void arch_suspend_disable_irqs(void)
+{
+	if (ppc_md.suspend_disable_irqs)
+		ppc_md.suspend_disable_irqs();
+	else
+		generic_suspend_disable_irqs();

Any particular reason why we need a ppc_md hook here?  Do we expect
some platform to need to do something different?

Paul.

Paul Mackerras wrote:

It might be better to use hard_irq_disable rather than
local_irq_disable here, since I think we will need that on 64-bit (and
on 32-bit if we ever do lazy irq disabling there).

OK.

quoted

+/* Overrides the weak version in kernel/power/main.c */
+void arch_suspend_disable_irqs(void)
+{
+	if (ppc_md.suspend_disable_irqs)
+		ppc_md.suspend_disable_irqs();
+	else
+		generic_suspend_disable_irqs();

Any particular reason why we need a ppc_md hook here?  Do we expect
some platform to need to do something different?

Not that I know the details of, but others requested it.

-Scott

On Wed, 2007-09-12 at 07:16 +1000, Paul Mackerras wrote:

quoted

+/* Overrides the weak version in kernel/power/main.c */
+void arch_suspend_disable_irqs(void)
+{
+	if (ppc_md.suspend_disable_irqs)
+		ppc_md.suspend_disable_irqs();
+	else
+		generic_suspend_disable_irqs();

Any particular reason why we need a ppc_md hook here?  Do we expect
some platform to need to do something different?

Yes, we need to hook into these for the PMU and platform functions on
powermac. Once I get to convert that to the generic infrastructure...

johannes