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Subject[PATCH 09/10] PPS: low level IRQ timestamps recording.
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 | 18 ++++++++++++++++++
arch/x86/kernel/irq_64.c | 22 ++++++++++++++++++++--
drivers/pps/Kconfig | 12 ++++++++++++
drivers/pps/clients/pps-ldisc.c | 18 ++++++++++++++++++
include/linux/pps.h | 1 +
5 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index 1cf8c1f..3013d0d 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 pps_ktime pps_irq_ts[NR_IRQS];
+EXPORT_SYMBOL(pps_irq_ts);
+#endif
+
/*
* 'what should we do if we get a hw irq event on an illegal vector'.
* each architecture has to answer this themselves.
@@ -225,6 +231,12 @@ unsigned int do_IRQ(struct pt_regs *regs)
/* high bit used in ret_from_ code */
int overflow, irq = ~regs->orig_ax;
struct irq_desc *desc = irq_desc + irq;
+#ifdef CONFIG_PPS_IRQ_EVENTS
+ struct timespec __ts;
+
+ /* Get IRQ timestamps as soon as possible for the PPS layer */
+ getnstimeofday(&__ts);
+#endif

if (unlikely((unsigned)irq >= NR_IRQS)) {
printk(KERN_EMERG "%s: cannot handle IRQ %d\n",
@@ -232,6 +244,12 @@ 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].sec = __ts.tv_sec;
+ pps_irq_ts[irq].nsec = __ts.tv_nsec;
+#endif
+
old_regs = set_irq_regs(regs);
irq_enter();

diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 1f78b23..1ea77a7 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -17,9 +17,15 @@
#include <asm/io_apic.h>
#include <asm/idle.h>
#include <asm/smp.h>
+#include <linux/pps.h>

atomic_t irq_err_count;

+#ifdef CONFIG_PPS_IRQ_EVENTS
+struct pps_ktime pps_irq_ts[NR_IRQS];
+EXPORT_SYMBOL(pps_irq_ts);
+#endif
+
/*
* 'what should we do if we get a hw irq event on an illegal vector'.
* each architecture has to answer this themselves.
@@ -188,6 +194,12 @@ u64 arch_irq_stat(void)
asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
+#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;
@@ -201,9 +213,15 @@ asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
stack_overflow_check(regs);
#endif

- if (likely(irq < NR_IRQS))
+ if (likely(irq < NR_IRQS)) {
+#ifdef CONFIG_PPS_IRQ_EVENTS
+ /* Then, after sanity check, store the IRQ timestamp */
+ pps_irq_ts[irq].sec = __ts.tv_sec;
+ pps_irq_ts[irq].nsec = __ts.tv_nsec;
+#endif
+
generic_handle_irq(irq);
- 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/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
index f1efa26..20d2c2e 100644
--- a/drivers/pps/clients/pps-ldisc.c
+++ b/drivers/pps/clients/pps-ldisc.c
@@ -26,6 +26,22 @@

#define PPS_TTY_MAGIC 0x0001

+#ifdef CONFIG_PPS_IRQ_EVENTS
+
+static void pps_tty_dcd_change(struct uart_port *port, unsigned int status,
+ struct timespec *ts)
+{
+ int id = (int) port->info->port.tty->disc_data;
+
+ pps_event(id, &pps_irq_ts[port->irq],
+ status ? PPS_CAPTUREASSERT : PPS_CAPTURECLEAR, port);
+
+ pr_debug("[IRQev] PPS %s at %lu on source #%d\n",
+ status ? "assert" : "clear", jiffies, id);
+}
+
+#else
+
static void pps_tty_dcd_change(struct uart_port *port, unsigned int status,
struct timespec *ts)
{
@@ -53,6 +69,8 @@ static void pps_tty_dcd_change(struct uart_port *port, unsigned int status,
status ? "assert" : "clear", jiffies, id);
}

+#endif /* CONFIG_PPS_IRQ_EVENTS */
+
static int pps_tty_open(struct tty_struct *tty)
{
struct pps_source_info info;
diff --git a/include/linux/pps.h b/include/linux/pps.h
index 53e171c..bb9a2e6 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 pps_ktime pps_irq_ts[];

extern struct device_attribute pps_attrs[];

--
1.5.4.3


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