diff options
Diffstat (limited to 'include/hw/ptimer.h')
| -rw-r--r-- | include/hw/ptimer.h | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/include/hw/ptimer.h b/include/hw/ptimer.h index c443218475..4dc02b0de4 100644 --- a/include/hw/ptimer.h +++ b/include/hw/ptimer.h @@ -33,9 +33,17 @@ * to stderr when the guest attempts to enable the timer. */ -/* The default ptimer policy retains backward compatibility with the legacy - * timers. Custom policies are adjusting the default one. Consider providing - * a correct policy for your timer. +/* + * The 'legacy' ptimer policy retains backward compatibility with the + * traditional ptimer behaviour from before policy flags were introduced. + * It has several weird behaviours which don't match typical hardware + * timer behaviour. For a new device using ptimers, you should not + * use PTIMER_POLICY_LEGACY, but instead check the actual behaviour + * that you need and specify the right set of policy flags to get that. + * + * If you are overhauling an existing device that uses PTIMER_POLICY_LEGACY + * and are in a position to check or test the real hardware behaviour, + * consider updating it to specify the right policy flags. * * The rough edges of the default policy: * - Starting to run with a period = 0 emits error message and stops the @@ -54,7 +62,7 @@ * since the last period, effectively restarting the timer with a * counter = counter value at the moment of change (.i.e. one less). */ -#define PTIMER_POLICY_DEFAULT 0 +#define PTIMER_POLICY_LEGACY 0 /* Periodic timer counter stays with "0" for a one period before wrapping * around. */ |