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From: Dmitry Osipenko <digetx@gmail.com>
Message-ID: <56A4E6E9.2010103@gmail.com>
Date: Sun, 24 Jan 2016 17:59:53 +0300
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Subject: Re: [Qemu-devel] [PATCH v11 7/7] arm_mptimer: Convert to use ptimer
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To: Peter Crosthwaite <crosthwaitepeter@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-arm <qemu-arm@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>

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