Op ma 19 nov. 2018 om 02:10 schreef Finn Thain <fth...@telegraphics.com.au>: > > hp300_gettimeoffset() never checks the timer interrupt flag and will > fail to notice when the timer counter gets reloaded. That means the > clock could jump backwards. > > Remove this code and leave this platform on the 'jiffies' clocksource. > Note that this amounts to a regression in clock precision. However, > adopting the 'jiffies' clocksource does resolve the monotonicity issue. > > Signed-off-by: Finn Thain <fth...@telegraphics.com.au> > --- > hp300_gettimeoffset() cannot be used in a clocksource conversion > unless it can be made monotonic. I can't fix this without knowing the > details of the timer implementation, such as the relationship between > the timer count and the interrupt flag.
I don't really like this regression... According to NetBSD sources, there are 3 timers in the chip (originally an MC6840 PTM). Timer 1 is used as the system timer, timer 3 runs at the same rate and is unused on Linux (on NetBSD it is used as the statistics/profiling timer), and timer 3 is connected to timer 2 so you can make a 32-bit timer out of the two timers together (also unused on Linux). Timers 1 counts down at 25 MHz. The interrupt flag is set when the counter reaches 0 after which it is automatically reloaded and starts counting down again. > --- > arch/m68k/hp300/time.c | 19 ------------------- > 1 file changed, 19 deletions(-)
