[PATCH 9/9] PPS: low level IRQ timestamps recording.

[Rodolfo Giometti <giometti@linux.it>]

Add low level IRQ timestamps recording for x86 (32 and 64 bits)
platforms and enable UART clients in order to use it.

This improves PPS precision. :)

Signed-off-by: Rodolfo Giometti <giometti@linux.it>
---
 arch/x86/kernel/irq_32.c    |   16 ++++++++++++++++
 arch/x86/kernel/irq_64.c    |   21 +++++++++++++++++++--
 drivers/pps/Kconfig         |   12 ++++++++++++
 include/linux/pps.h         |    1 +
 include/linux/serial_core.h |    7 ++++++-
 5 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index a513826..7fce1e2 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -15,6 +15,7 @@
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/delay.h>
+#include <linux/pps.h>
 
 #include <asm/apic.h>
 #include <asm/uaccess.h>
@@ -25,6 +26,11 @@ EXPORT_PER_CPU_SYMBOL(irq_stat);
 DEFINE_PER_CPU(struct pt_regs *, irq_regs);
 EXPORT_PER_CPU_SYMBOL(irq_regs);
 
+#ifdef CONFIG_PPS_IRQ_EVENTS
+struct timespec pps_irq_ts[NR_IRQS];
+EXPORT_SYMBOL(pps_irq_ts);
+#endif
+
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
 /* Debugging check for stack overflow: is there less than 1KB free? */
 static int check_stack_overflow(void)
@@ -204,7 +210,12 @@ unsigned int do_IRQ(struct pt_regs *regs)
 	unsigned vector = ~regs->orig_ax;
 	struct irq_desc *desc;
 	unsigned irq;
+#ifdef CONFIG_PPS_IRQ_EVENTS
+	struct timespec ts;
 
+	/* Get IRQ timestamps as soon as possible for the PPS layer */
+	getnstimeofday(&ts);
+#endif
 
 	old_regs = set_irq_regs(regs);
 	irq_enter();
@@ -219,6 +230,11 @@ unsigned int do_IRQ(struct pt_regs *regs)
 		BUG();
 	}
 
+#ifdef CONFIG_PPS_IRQ_EVENTS
+	/* Then, after sanity check, store the IRQ timestamp */
+	pps_irq_ts[irq] = ts;
+#endif
+
 	if (!execute_on_irq_stack(overflow, desc, irq)) {
 		if (unlikely(overflow))
 			print_stack_overflow();
diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 60eb84e..a1457a0 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -17,6 +17,12 @@
 #include <asm/io_apic.h>
 #include <asm/idle.h>
 #include <asm/smp.h>
+#include <linux/pps.h>
+
+#ifdef CONFIG_PPS_IRQ_EVENTS
+struct timespec pps_irq_ts[NR_IRQS];
+EXPORT_SYMBOL(pps_irq_ts);
+#endif
 
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
 /*
@@ -51,6 +57,12 @@ asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 	struct irq_desc *desc;
+#ifdef CONFIG_PPS_IRQ_EVENTS
+	struct timespec ts;
+
+	/* Get IRQ timestamps as soon as possible for the PPS layer */
+	getnstimeofday(&ts);
+#endif
 
 	/* high bit used in ret_from_ code  */
 	unsigned vector = ~regs->orig_ax;
@@ -65,9 +77,14 @@ asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
 #endif
 
 	desc = irq_to_desc(irq);
-	if (likely(desc))
+	if (likely(desc)) {
+#ifdef CONFIG_PPS_IRQ_EVENTS
+		/* Then, after sanity check, store the IRQ timestamp */
+		pps_irq_ts[irq] = ts;
+#endif
+
 		generic_handle_irq_desc(irq, desc);
-	else {
+	} else {
 		if (!disable_apic)
 			ack_APIC_irq();
 
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
index 1afe4e0..7c0b094 100644
--- a/drivers/pps/Kconfig
+++ b/drivers/pps/Kconfig
@@ -22,6 +22,18 @@ config PPS
 	  To compile this driver as a module, choose M here: the module
 	  will be called pps_core.ko.
 
+config PPS_IRQ_EVENTS
+	bool "Use low level IRQ timestamps"
+	depends on PPS && (X86_32 || X86_64)
+	default yes
+	help
+	  Say Y here if you wish using low level IRQ timestamps to register
+	  PPS events.
+
+	  This should improve PPS resolution but it delays echo functions
+	  call. Note also that this function is not implemented on all
+	  platforms and PPS clients!
+
 config PPS_DEBUG
 	bool "PPS debugging messages"
 	depends on PPS
diff --git a/include/linux/pps.h b/include/linux/pps.h
index b5c3cf9..191190e 100644
--- a/include/linux/pps.h
+++ b/include/linux/pps.h
@@ -181,6 +181,7 @@ struct pps_device {
 
 extern spinlock_t pps_idr_lock;
 extern struct idr pps_idr;
+extern struct timespec pps_irq_ts[];
 
 extern struct device_attribute pps_attrs[];
 
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index cd6af20..eac89e6 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -168,6 +168,7 @@
 #include <linux/tty.h>
 #include <linux/mutex.h>
 #include <linux/sysrq.h>
+#include <linux/pps.h>
 
 struct uart_port;
 struct uart_info;
@@ -495,7 +496,11 @@ uart_handle_dcd_change(struct uart_port *port, unsigned int status)
 	struct timespec ts;
 
 	if (ld && ld->ops->dcd_change)
+#ifdef CONFIG_PPS_IRQ_EVENTS
+		ts = pps_irq_ts[port->irq];
+#else
 		getnstimeofday(&ts);
+#endif
 
 	port->icount.dcd++;
 #ifdef CONFIG_HARD_PPS
@@ -511,7 +516,7 @@ uart_handle_dcd_change(struct uart_port *port, unsigned int status)
 	}
 
 	if (ld && ld->ops->dcd_change)
-		ld->ops->dcd_change(port, status, &ts);
+		ld->ops->dcd_change(info->port.tty, status, &ts);
 	if (ld)
 		tty_ldisc_deref(ld);
 }
-- 
1.5.4.3