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Re: [Qemu-devel] [PATCH v11 7/7] arm_mptimer: Convert to use ptimer


From: Dmitry Osipenko
Subject: Re: [Qemu-devel] [PATCH v11 7/7] arm_mptimer: Convert to use ptimer
Date: Sun, 24 Jan 2016 17:59:53 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0

Hello Peter,

24.01.2016 08:25, Peter Crosthwaite пишет:

[snip]

+        timerblock_run(tb->timer, control, (value != 0) && (control & 1));
          break;
      case 8: /* Control.  */
-        old = tb->control;
-        tb->control = value;
-        if (value & 1) {
-            if ((old & 1) && (tb->count != 0)) {
-                /* Do nothing if timer is ticking right now.  */
-                break;
+        if ((value & 1) && (control & 3) != (value & 3)) {
+            uint64_t count = (value & 0xff00) ? 1 : 
ptimer_get_count(tb->timer);
+            if ((count == 0) && (value & 2)) {
+                timerblock_set_count(tb->timer, value, &count);

This looks like a weird corner-case, what does it do exactly? I can't
follow it so it needs a comment :)


It does the following:

mode     | prescaler | reload if counter == 0 | tick immediately if counter == 0
--------------------------------------------------------------------------------
oneshot      == 0               0                         0
oneshot      != 0               0                         1
periodic     == 0               1                         0
periodic     != 0               0                         1

If writing control register with prescaler = 0, then for one-shot timer with counter == 0 or periodic timer with load = counter == 0 this is NOP. Will add a comment.

Thanks for review!

--
Dmitry



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