Adapt to kernel 5.6+ time API changes

Building EtherCAT master debug ring on Linux v6.6 Phytium kernel
failed with:
- incomplete type 'struct timeval'
- struct timespec64 has no tv_usec member
- implicit function declaration do_gettimeofday

Linux 5.6 upstream deprecated timeval/do_gettimeofday and migrated
fully to timespec64.

Conditional compile based on LINUX_VERSION_CODE >= KERNEL_VERSION(5,6,0):
- Header: include linux/version.h in device.h for version judgment
- Data structure: ec_debug_frame_t / ec_device use timespec64 for new
  kernel, timeval for legacy
- Time subtraction: custom timerspec64_sub to replace timersub on new
  kernel
- Timestamp fetch: ktime_get_real_ts64 (5.6+), do_gettimeofday (legacy)
- Member initialization: tv_nsec / tv_usec assigned conditionally
- Log printing: divide tv_nsec by 1000 to restore us display, unified
  log format

Signed-off-by: powertree <powertree@163.com>

master/device.c

@@ -35,6 +35,7 @@
 #include "master.h"
 
 #ifdef EC_DEBUG_RING
+#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 6, 0)
 #define timersub(a, b, result) \
     do { \
         (result)->tv_sec = (a)->tv_sec - (b)->tv_sec; \
@@ -45,6 +46,7 @@
         } \
     } while (0)
 #endif
+#endif
 
 /****************************************************************************/
 
@@ -85,7 +87,11 @@ int ec_device_init(
 #endif
 #ifdef EC_DEBUG_RING
     device->timeval_poll.tv_sec = 0;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+    device->timeval_poll.tv_nsec = 0;
+#else
     device->timeval_poll.tv_usec = 0;
+#endif
 #endif
     device->jiffies_poll = 0;
 
@@ -96,7 +102,11 @@ int ec_device_init(
         ec_debug_frame_t *df = &device->debug_frames[i];
         df->dir = TX;
         df->t.tv_sec = 0;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+        df->t.tv_nsec = 0;
+#else
         df->t.tv_usec = 0;
+#endif
         memset(df->data, 0, EC_MAX_DATA_SIZE);
         df->data_size = 0;
     }
@@ -397,7 +407,11 @@ void ec_device_debug_ring_append(
 
     df->dir = dir;
     if (dir == TX) {
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+        ktime_get_real_ts64(&df->t);
+#else
         do_gettimeofday(&df->t);
+#endif
     }
     else {
         df->t = device->timeval_poll;
@@ -422,7 +436,11 @@ void ec_device_debug_ring_print(
     int i;
     unsigned int ring_index;
     const ec_debug_frame_t *df;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+    struct timespec64 t0, diff;
+#else
     struct timeval t0, diff;
+#endif
 
     // calculate index of the newest frame in the ring to get its time
     ring_index = (device->debug_frame_index + EC_DEBUG_RING_SIZE - 1)
@@ -437,13 +455,25 @@ void ec_device_debug_ring_print(
 
     for (i = 0; i < device->debug_frame_count; i++) {
         df = &device->debug_frames[ring_index];
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+        diff = timespec64_sub(t0, df->t);
+#else
         timersub(&t0, &df->t, &diff);
+#endif
 
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+        EC_MASTER_DBG(device->master, 1, "Frame %u, dt=%u.%06u s, %s:\n",
+                i + 1 - device->debug_frame_count,
+                (unsigned int) diff.tv_sec,
+                (unsigned int) (diff.tv_nsec / 1000),
+                (df->dir == TX) ? "TX" : "RX");
+#else
         EC_MASTER_DBG(device->master, 1, "Frame %u, dt=%u.%06u s, %s:\n",
                 i + 1 - device->debug_frame_count,
                 (unsigned int) diff.tv_sec,
                 (unsigned int) diff.tv_usec,
                 (df->dir == TX) ? "TX" : "RX");
+#endif
         ec_print_data(df->data, df->data_size);
 
         ring_index++;
@@ -469,7 +499,11 @@ void ec_device_poll(
 #endif
     device->jiffies_poll = jiffies;
 #ifdef EC_DEBUG_RING
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+    ktime_get_real_ts64(&device->timeval_poll);
+#else
     do_gettimeofday(&device->timeval_poll);
+#endif
 #endif
     device->poll(device->dev);
 }

master/device.h

@@ -47,6 +47,7 @@
 #endif
 
 #ifdef EC_DEBUG_RING
+#include <linux/version.h>
 #define EC_DEBUG_RING_SIZE 10
 
 typedef enum {
@@ -55,7 +56,11 @@ typedef enum {
 
 typedef struct {
     ec_debug_frame_dir_t dir;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+    struct timespec64 t;
+#else
     struct timeval t;
+#endif
     uint8_t data[EC_MAX_DATA_SIZE];
     unsigned int data_size;
 } ec_debug_frame_t;
@@ -84,7 +89,11 @@ struct ec_device
     cycles_t cycles_poll; /**< cycles of last poll */
 #endif
 #ifdef EC_DEBUG_RING
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
+    struct timespec64 timeval_poll;
+#else
     struct timeval timeval_poll;
+#endif
 #endif
     unsigned long jiffies_poll; /**< jiffies of last poll */