Hi All, I try to handle "V4L2: vivid: improve timestamping" task in https://www.linuxtv.org/wiki/index.php/Media_Open_Source_Projects:_Looking_for_Volunteers I do a first try on using hrtimer on vivi-kthread-touch.c I have some doubt on my things :'( In particular on the following formulas: buffers_since_start = denominator * time_since_start / NSEC_PER_SEC; next_time_buf_start = time_since_start / buffers_since_start; I post also the entire hrtimer func: static enum hrtimer_restart vivid_hrtimer_touch_cap(struct hrtimer *hrtimer) { struct vivid_dev *dev = container_of(hrtimer, struct vivid_dev, hrtimer_touch_cap); unsigned int numerator, denominator; ktime_t now; s64 time_since_start, next_time_buf_start; u64 buffers_since_start, numerators_since_start; int dropped_bufs; /* Resets frame counters first time */ if (!dev->hrtimer_touch_cap_started) { dprintk(dev, 1, "Touch Capture Thread Start\n"); dev->touch_cap_seq_offset = 0; dev->touch_cap_seq_count = 0; dev->touch_cap_seq_resync = false; dev->time_touch_cap = hrtimer_cb_get_time(hrtimer); if (dev->time_wrap) dev->time_wrap_offset = dev->time_wrap - ktime_get_ns(); else dev->time_wrap_offset = 0; dev->hrtimer_touch_cap_started = true; } now = hrtimer_cb_get_time(hrtimer); if (dev->touch_cap_seq_resync) { dev->time_touch_cap = hrtimer_cb_get_time(hrtimer); dev->touch_cap_seq_offset = dev->touch_cap_seq_count + 1; dev->touch_cap_seq_count = 0; dev->cap_seq_resync = false; } denominator = dev->timeperframe_tch_cap.denominator; numerator = dev->timeperframe_tch_cap.numerator; time_since_start = ktime_to_ns(now) - ktime_to_ns(dev->time_touch_cap); // printk("ktime_to_ms(now) = %lld", ktime_to_ms(now)); // printk("ktime_to_ms(dev->time_touch_cap) = %lld", ktime_to_ms(dev->time_touch_cap)); // printk("time_since_start = %lld\n",time_since_start); buffers_since_start = denominator * time_since_start / NSEC_PER_SEC; // printk("buffer_since_start = %lld\n",buffers_since_start); dropped_bufs = buffers_since_start + dev->touch_cap_seq_offset - dev->touch_cap_seq_count; dev->touch_cap_seq_count = buffers_since_start + dev->touch_cap_seq_offset; dev->touch_cap_with_seq_wrap_count = dev->touch_cap_seq_count - dev->touch_cap_seq_start; vivid_thread_tch_cap_tick(dev, dropped_bufs); numerators_since_start = ++buffers_since_start * numerator; now = hrtimer_cb_get_time(hrtimer); time_since_start = ktime_to_ns(now) - ktime_to_ns(dev->time_touch_cap); // printk("time_since_start = %lld\n",time_since_start); mutex_unlock(&dev->mutex); next_time_buf_start = time_since_start / buffers_since_start; // printk("next_time_buf_start = %lld", next_time_buf_start); hrtimer_forward_now(hrtimer, ns_to_ktime(next_time_buf_start)); return HRTIMER_RESTART; } References: - https://github.com/Scott31393/linux/commit/b0e7b7eea1921ab3faad46c8ad8538c083cac2b4 During test I got the following result, delta is quite costant but sometimes I got some delay of 2 time the, let me say "nice to have delay". /usr/bin/v4l2-ctl -d /dev/v4l-touch0 --stream-mmap --verbose cap dqbuf: 1 seq: 3839 bytesused: 504 ts: 628.527612 delta: 99.995 ms fps: 10.00 (ts-monotonic, ts-src-eof) TD16: 0 1 0 0 0 0 0 0 0 0 0 0 -3 -1 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 TD16: 0 3 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 TD16: 0 0 0 1 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 -1 0 TD16: 0 0 0 0 -1 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 2 0 0 0 0 0 TD16: 3 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 3 0 TD16: 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 3 cap dqbuf: 2 seq: 3840 bytesused: 504 ts: 628.627602 delta: 99.990 ms fps: 10.00 (ts-monotonic, ts-src-eof) TD16: 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 2 0 0 TD16: 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 -2 0 2 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 2 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 -2 0 0 0 -3 0 0 0 -1 0 0 0 1 0 0 0 0 0 TD16: -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -3 0 0 0 0 0 TD16: 0 3 0 -3 1 0 0 -3 0 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 1 0 0 0 0 0 0 -3 0 0 0 0 0 0 0 0 0 0 0 0 3 TD16: 0 1 0 0 0 2 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 cap dqbuf: 3 seq: 3841 bytesused: 504 ts: 628.727597 delta: 99.995 ms fps: 10.00 (ts-monotonic, ts-src-eof) TD16: 0 1 0 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 -1 0 -1 -3 0 0 -1 0 0 -3 0 0 TD16: 0 0 0 0 -1 3 0 0 0 0 0 0 0 -1 0 0 0 0 -2 0 0 TD16: 0 0 0 -1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -2 0 0 0 0 0 TD16: 0 0 0 0 0 0 2 0 0 0 2 0 0 0 0 0 0 0 0 0 0 TD16: 0 0 0 0 0 -3 0 0 0 0 1 0 0 0 0 0 0 -3 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 -2 0 0 0 0 3 0 -3 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -2 0 0 TD16: 0 0 0 0 0 0 0 0 -1 0 3 0 0 0 0 2 0 0 0 1 0 TD16: 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 -1 0 0 0 0 0 0 TD16: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 cap dqbuf: 0 seq: 3843 bytesused: 504 ts: 628.927577 delta: 199.980 ms fps: 10.00 dropped: 1 (ts-monotonic, ts-src-eof) This is just a work in progress. For this reason I don't post the entire patch. But if we need I can post it too :) Let me know. What do you think about. Thanks in advance. Tommaso -- Tommaso Merciai Embedded Linux Engineer tommaso.merciai@xxxxxxxxxxxxxxxxxxxx __________________________________ Amarula Solutions SRL Via Le Canevare 30, 31100 Treviso, Veneto, IT T. +39 042 243 5310 info@xxxxxxxxxxxxxxxxxxxx www.amarulasolutions.com
