Re: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in tc_link_training()

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On 04/12/2019 20:27, Tomi Valkeinen wrote:
Hi Andrey,

On 19/06/2019 08:27, Andrey Smirnov wrote:

@@ -748,22 +748,19 @@ static int tc_set_video_mode(struct tc_data *tc,
  static int tc_wait_link_training(struct tc_data *tc)
  {
-    u32 timeout = 1000;
      u32 value;
      int ret;
-    do {
-        udelay(1);
-        tc_read(DP0_LTSTAT, &value);
-    } while ((!(value & LT_LOOPDONE)) && (--timeout));
-
-    if (timeout == 0) {
+    ret = tc_poll_timeout(tc, DP0_LTSTAT, LT_LOOPDONE,
+                  LT_LOOPDONE, 1, 1000);

This seems to break DP at least with some monitors for me. I think it's just a timeout problem, as increasing the values helps.

Using ktime, I can see that during link training, the first call takes ~2ms, the second ~7ms. I think this worked before, as udelay(1) takes much longer than 1 us.

Also the timeout in tc_aux_link_setup takes ~500us for me, and max is 1000us. So it works, but I think it's a bit tight.

 Tomi

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