firewire: cdev: add more flexible cycle timer ioctl

The system time from CLOCK_REALTIME is not monotonic, hence problematic
for the main user of the FW_CDEV_IOC_GET_CYCLE_TIMER ioctl.  This issue
exists in its successor ABI, i.e. raw1394, too.
http://subversion.ffado.org/ticket/242

We now offer an alternative ioctl which lets the caller choose between
CLOCK_REALTIME, CLOCK_MONOTONIC, and CLOCK_MONOTONIC_RAW as source of
the local time, very similar to the clock_gettime libc function.  The
format of the local time return value matches that of clock_gettime
(seconds and nanoseconds, instead of a single microseconds value from
the existing ioctl).

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

2 files changed, 59 insertions, 10 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index 3c1ac0933d24..a4aa477b9b2c 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1031,22 +1031,46 @@ static int ioctl_stop_iso(struct client *client, void *buffer)
         return fw_iso_context_stop(client->iso_context);
 }
 
-static int ioctl_get_cycle_timer(struct client *client, void *buffer)
+static int ioctl_get_cycle_timer2(struct client *client, void *buffer)
 {
-        struct fw_cdev_get_cycle_timer *request = buffer;
+        struct fw_cdev_get_cycle_timer2 *request = buffer;
         struct fw_card *card = client->device->card;
-        struct timeval tv;
+        struct timespec ts = {0, 0};
         u32 cycle_time;
+        int ret = 0;
 
         local_irq_disable();
 
         cycle_time = card->driver->get_cycle_time(card);
-        do_gettimeofday(&tv);
+
+        switch (request->clk_id) {
+        case CLOCK_REALTIME:      getnstimeofday(&ts);                   break;
+        case CLOCK_MONOTONIC:     do_posix_clock_monotonic_gettime(&ts); break;
+        case CLOCK_MONOTONIC_RAW: getrawmonotonic(&ts);                  break;
+        default:
+                ret = -EINVAL;
+        }
 
         local_irq_enable();
 
-        request->local_time = tv.tv_sec * 1000000ULL + tv.tv_usec;
-        request->cycle_timer = cycle_time;
+        request->tv_sec         = ts.tv_sec;
+        request->tv_nsec        = ts.tv_nsec;
+        request->cycle_timer    = cycle_time;
+
+        return ret;
+}
+
+static int ioctl_get_cycle_timer(struct client *client, void *buffer)
+{
+        struct fw_cdev_get_cycle_timer *request = buffer;
+        struct fw_cdev_get_cycle_timer2 ct2;
+
+        ct2.clk_id = CLOCK_REALTIME;
+        ioctl_get_cycle_timer2(client, &ct2);
+
+        request->local_time     = ct2.tv_sec * USEC_PER_SEC +
+                                  ct2.tv_nsec / NSEC_PER_USEC;
+        request->cycle_timer    = ct2.cycle_timer;
 
         return 0;
 }
@@ -1320,6 +1344,7 @@ static int (* const ioctl_handlers[])(struct client *client, void *buffer) = {
         ioctl_get_speed,
         ioctl_send_broadcast_request,
         ioctl_send_stream_packet,
+        ioctl_get_cycle_timer2,
 };
 
 static int dispatch_ioctl(struct client *client,
@@ -1341,6 +1366,7 @@ static int dispatch_ioctl(struct client *client,
                 struct fw_cdev_get_cycle_timer          _0c;
                 struct fw_cdev_allocate_iso_resource    _0d;
                 struct fw_cdev_send_stream_packet       _13;
+                struct fw_cdev_get_cycle_timer2         _14;
         })];
         int ret;
 
diff --git a/include/linux/firewire-cdev.h b/include/linux/firewire-cdev.h
index 520ecf86cbb3..baa8290c8416 100644
--- a/include/linux/firewire-cdev.h
+++ b/include/linux/firewire-cdev.h
@@ -248,6 +248,9 @@ union fw_cdev_event {
 #define FW_CDEV_IOC_SEND_BROADCAST_REQUEST       _IOW('#', 0x12, struct fw_cdev_send_request)
 #define FW_CDEV_IOC_SEND_STREAM_PACKET           _IOW('#', 0x13, struct fw_cdev_send_stream_packet)
 
+/* available since kernel version 2.6.34 */
+#define FW_CDEV_IOC_GET_CYCLE_TIMER2   _IOWR('#', 0x14, struct fw_cdev_get_cycle_timer2)
+
 /*
  * FW_CDEV_VERSION History
  *  1  (2.6.22)  - initial version
@@ -544,14 +547,15 @@ struct fw_cdev_stop_iso {
 /**
  * struct fw_cdev_get_cycle_timer - read cycle timer register
  * @local_time:   system time, in microseconds since the Epoch
- * @cycle_timer:  isochronous cycle timer, as per OHCI 1.1 clause 5.13
+ * @cycle_timer:  Cycle Time register contents
  *
  * The %FW_CDEV_IOC_GET_CYCLE_TIMER ioctl reads the isochronous cycle timer
- * and also the system clock.  This allows to express the receive time of an
- * isochronous packet as a system time with microsecond accuracy.
+ * and also the system clock (%CLOCK_REALTIME).  This allows to express the
+ * receive time of an isochronous packet as a system time.
  *
  * @cycle_timer consists of 7 bits cycleSeconds, 13 bits cycleCount, and
- * 12 bits cycleOffset, in host byte order.
+ * 12 bits cycleOffset, in host byte order.  Cf. the Cycle Time register
+ * per IEEE 1394 or Isochronous Cycle Timer register per OHCI-1394.
  */
 struct fw_cdev_get_cycle_timer {
         __u64 local_time;
@@ -559,6 +563,25 @@ struct fw_cdev_get_cycle_timer {
 };
 
 /**
+ * struct fw_cdev_get_cycle_timer2 - read cycle timer register
+ * @tv_sec:       system time, seconds
+ * @tv_nsec:      system time, sub-seconds part in nanoseconds
+ * @clk_id:       input parameter, clock from which to get the system time
+ * @cycle_timer:  Cycle Time register contents
+ *
+ * The %FW_CDEV_IOC_GET_CYCLE_TIMER2 works like
+ * %FW_CDEV_IOC_GET_CYCLE_TIMER but lets you choose a clock like with POSIX'
+ * clock_gettime function.  Supported @clk_id values are POSIX' %CLOCK_REALTIME
+ * and %CLOCK_MONOTONIC and Linux' %CLOCK_MONOTONIC_RAW.
+ */
+struct fw_cdev_get_cycle_timer2 {
+        __s64 tv_sec;
+        __s32 tv_nsec;
+        __s32 clk_id;
+        __u32 cycle_timer;
+};
+
+/**
  * struct fw_cdev_allocate_iso_resource - (De)allocate a channel or bandwidth
  * @closure:    Passed back to userspace in correponding iso resource events
  * @channels:   Isochronous channels of which one is to be (de)allocated