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timer session: add elapsed_us method

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As timer sessions are not expected to be microseconds precise (because
of RPC latency and scheduling), the session interface provided only a
method 'elapsed_ms' although the back end of this method in the timer
driver works with microseconds.

However, in some cases it makes sense to have a method 'elapsed_us'. The
values it returns might be milliseconds away from the "real" time but it
allows you to work with delays smaller than a millisecond without
getting a zero delta value.

This commit is motivated by the need for fast bursts of calibration
steps for the time interpolation in the new timer connection.

Ref #2400
This commit is contained in:
Martin Stein 2017-08-04 15:11:27 +02:00 committed by Christian Helmuth
parent f7f2c86c41
commit 8750e373a0
3 changed files with 11 additions and 3 deletions
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2
repos/os/include/timer_session/client.h
View File

@ -34,6 +34,8 @@ struct Timer::Session_client : Genode::Rpc_client<Session>
void sigh(Signal_context_capability sigh) override { call<Rpc_sigh>(sigh); }
unsigned long elapsed_ms() const override { return call<Rpc_elapsed_ms>(); }
unsigned long elapsed_us() const override { return call<Rpc_elapsed_us>(); }
};
#endif /* _INCLUDE__TIMER_SESSION__CLIENT_H_ */

5
repos/os/include/timer_session/timer_session.h
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@ -58,6 +58,8 @@ struct Timer::Session : Genode::Session
*/
virtual unsigned long elapsed_ms() const = 0;
virtual unsigned long elapsed_us() const = 0;
/**
* Client-side convenience method for sleeping the specified number
* of milliseconds
@ -79,9 +81,10 @@ struct Timer::Session : Genode::Session
GENODE_RPC(Rpc_trigger_periodic, void, trigger_periodic, unsigned);
GENODE_RPC(Rpc_sigh, void, sigh, Genode::Signal_context_capability);
GENODE_RPC(Rpc_elapsed_ms, unsigned long, elapsed_ms);
GENODE_RPC(Rpc_elapsed_us, unsigned long, elapsed_us);
GENODE_RPC_INTERFACE(Rpc_trigger_once, Rpc_trigger_periodic,
Rpc_sigh, Rpc_elapsed_ms);
Rpc_sigh, Rpc_elapsed_ms, Rpc_elapsed_us);
};
#endif /* _INCLUDE__TIMER_SESSION__TIMER_SESSION_H_ */

7
repos/os/src/drivers/timer/include/session_component.h
View File

@ -71,8 +71,11 @@ class Timer::Session_component : public Genode::Rpc_object<Session>,
}
unsigned long elapsed_ms() const override {
return (_timeout_scheduler.curr_time().trunc_to_plain_us().value -
_init_time_us) / 1000; }
return elapsed_us() / 1000; }
unsigned long elapsed_us() const override {
return _timeout_scheduler.curr_time().trunc_to_plain_us().value -
_init_time_us; }
void msleep(unsigned) override { /* never called at the server side */ }
void usleep(unsigned) override { /* never called at the server side */ }