On 05/05/2015 04:17 PM, Marek Vasut wrote:
On Tuesday, May 05, 2015 at 11:46:56 PM, Stephen Warren wrote:
On 05/04/2015 02:54 PM, Marek Vasut wrote:
Switch to generic timer implementation from lib/time.c .
This also fixes a signed overflow which was in __udelay()
implementation.
Can you explain that a bit more?
-void __udelay(unsigned long usec)
-{
- ulong endtime;
- signed long diff;
-
- endtime = get_timer_us(0) + usec;
-
- do {
- ulong now = get_timer_us(0);
- diff = endtime - now;
- } while (diff >= 0);
-}
I believe since endtime and now hold micro seconds, there shouldn't be
any overflow so long as the microsecond difference fits into 31 bits,
i.e. so long as usec is less than ~36 minutes. I doubt anything is
calling __udelay() with that large of a value. Perhaps the issue this
patch fixes is in get_timer_us(0) instead, or something else changed as
a side-effect?
The generic implementation caters for full 32-bit range, that's all.
Since the argument of this function is unsigned, it can overflow if
you use argument which is bigger than 31 bits. OK like that ?
Sorry, I still don't understand. Both the __udelay() here and in
lib/time.c take an unsigned long argument. I don't see how switching one
out for the other can affect anything if the argument type is the issue.
Besides, what's passing a value >~36 minutes to udelay()?
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