stm class: p_sys-t: Add support for CLOCKSYNC packets

This adds support for CLOCKSYNC SyS-T packets, that establish correlation
between the transport clock (STP timestamps) and SyS-T timestamps. These
packets are sent periodically to allow the decoder to keep both time
sources in sync.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 80 insertions, 0 deletions

diff --git a/drivers/hwtracing/stm/p_sys-t.c b/drivers/hwtracing/stm/p_sys-t.c
index ffeb057b777c..b178a5495b67 100644
--- a/drivers/hwtracing/stm/p_sys-t.c
+++ b/drivers/hwtracing/stm/p_sys-t.c
@@ -72,15 +72,20 @@ enum sys_t_message_string_subtype {
                          MIPI_SYST_SEVERITY(INFO)               | \
                          MIPI_SYST_OPT_GUID)
 
+#define CLOCK_SYNC_HEADER       (MIPI_SYST_TYPES(CLOCK, TRANSPORT_SYNC) | \
+                                 MIPI_SYST_SEVERITY(MAX))
+
 struct sys_t_policy_node {
         uuid_t          uuid;
         bool            do_len;
         unsigned long   ts_interval;
+        unsigned long   clocksync_interval;
 };
 
 struct sys_t_output {
         struct sys_t_policy_node        node;
         unsigned long   ts_jiffies;
+        unsigned long   clocksync_jiffies;
 };
 
 static void sys_t_policy_node_init(void *priv)
@@ -191,10 +196,42 @@ sys_t_policy_ts_interval_store(struct config_item *item, const char *page,
 
 CONFIGFS_ATTR(sys_t_policy_, ts_interval);
 
+static ssize_t sys_t_policy_clocksync_interval_show(struct config_item *item,
+                                                    char *page)
+{
+        struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+
+        return sprintf(page, "%u\n", jiffies_to_msecs(pn->clocksync_interval));
+}
+
+static ssize_t
+sys_t_policy_clocksync_interval_store(struct config_item *item,
+                                      const char *page, size_t count)
+{
+        struct mutex *mutexp = &item->ci_group->cg_subsys->su_mutex;
+        struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+        unsigned int ms;
+        int ret;
+
+        mutex_lock(mutexp);
+        ret = kstrtouint(page, 10, &ms);
+        mutex_unlock(mutexp);
+
+        if (!ret) {
+                pn->clocksync_interval = msecs_to_jiffies(ms);
+                return count;
+        }
+
+        return ret;
+}
+
+CONFIGFS_ATTR(sys_t_policy_, clocksync_interval);
+
 static struct configfs_attribute *sys_t_policy_attrs[] = {
         &sys_t_policy_attr_uuid,
         &sys_t_policy_attr_do_len,
         &sys_t_policy_attr_ts_interval,
+        &sys_t_policy_attr_clocksync_interval,
         NULL,
 };
 
@@ -210,6 +247,43 @@ static inline bool sys_t_need_ts(struct sys_t_output *op)
         return false;
 }
 
+static bool sys_t_need_clock_sync(struct sys_t_output *op)
+{
+        if (op->node.clocksync_interval &&
+            time_after(op->clocksync_jiffies + op->node.clocksync_interval,
+                       jiffies)) {
+                op->clocksync_jiffies = jiffies;
+
+                return true;
+        }
+
+        return false;
+}
+
+static ssize_t
+sys_t_clock_sync(struct stm_data *data, unsigned int m, unsigned int c)
+{
+        u32 header = CLOCK_SYNC_HEADER;
+        const unsigned char nil = 0;
+        u64 payload[2]; /* Clock value and frequency */
+        ssize_t sz;
+
+        sz = data->packet(data, m, c, STP_PACKET_DATA, STP_PACKET_TIMESTAMPED,
+                          4, (u8 *)&header);
+        if (sz <= 0)
+                return sz;
+
+        payload[0] = ktime_get_real_ns();
+        payload[1] = NSEC_PER_SEC;
+        sz = stm_data_write(data, m, c, false, &payload, sizeof(payload));
+        if (sz <= 0)
+                return sz;
+
+        data->packet(data, m, c, STP_PACKET_FLAG, 0, 0, &nil);
+
+        return sizeof(header) + sizeof(payload);
+}
+
 static ssize_t sys_t_write(struct stm_data *data, struct stm_output *output,
                            unsigned int chan, const char *buf, size_t count)
 {
@@ -224,6 +298,12 @@ static ssize_t sys_t_write(struct stm_data *data, struct stm_output *output,
         if (!op)
                 return -EINVAL;
 
+        if (sys_t_need_clock_sync(op)) {
+                sz = sys_t_clock_sync(data, m, c);
+                if (sz <= 0)
+                        return sz;
+        }
+
         if (op->node.do_len)
                 header |= MIPI_SYST_OPT_LEN;
         if (sys_t_need_ts(op))