* Jon Hunter <jon-hunter@xxxxxx> [120910 15:00]: > > On 09/07/2012 05:22 PM, Tony Lindgren wrote: > > * Jon Hunter <jon-hunter@xxxxxx> [120905 12:05]: > >> The dmtimer functions to read and write the dmtimer registers are currently > >> defined as follows ... > >> > >> static inline u32 __omap_dm_timer_read(struct omap_dm_timer *timer, u32 reg, > >> int posted); > >> static inline void __omap_dm_timer_write(struct omap_dm_timer *timer, > >> u32 reg, u32 val, int posted); > >> > >> The posted variable indicates if the timer is configured to use the posted mode > >> when performing register accesses. The posted mode configuration of the dmtimer > >> is stored in the omap_dm_timer structure that is also being passed to the above > >> functions and therefore we do not need to pass the posted variable separately. > >> Therefore, simplify the above functions by removing the posted variable as an > >> argument as this is not necessary. > > > > I believe the reason for passing the posted flag was to optimize out some > > functions from the timer code as that's being run all the time. > > > > Care to check the assembly before and after this patch for the timer > > functions with objdump -d to make sure it does not add tons of bloat > > there? > > Hi Tony, > > Thanks for the details here. I see that makes sense and that the > compiler could take advantage of this as the functions are inlined. > > I have taken a look at the disassembled output using objdump as you > mentioned. What I see is ... > > 1. For dmtimer.c the impact appears negligible, the total number of > lines outputted by objdump only changed by 8 with (1215 lines) and > without (1207 lines) the patch applied. > > 2. For timer.c the impact is greater. I see that > omap2_gp_timer_set_next_event() increased by 6 instructions from 29 > to 35. clocksource_read_cycles() increased by 2 instructions 15 to > 17 instructions. dmtimer_read_sched_clock() increased by 2 > instructions from 17 to 19. omap2_gp_timer_set_mode() increased by > 21 instructions from 102 to 123. > > I imagine that we are mainly concerned about > omap2_gp_timer_set_next_event(), clocksource_read_cycles() and > dmtimer_read_sched_clock() as these will be called often. Therefore, I > am not sure if you wish to drop this patch. Well does it at lots of new ldr to the critical code? > By the way, if we do drop this patch, I would then need to fix the > setting of the posted variable in mach-omap2/timer.c for clock-source in > the case where a dmtimer is used. Today the code assumes that for > clock-source and clock-events posted mode is always used. However, with > the errata i103/i767 we will disable posted mode for clock-source on > omap2/3/4/5/am33xx devices. Yes I see, I guess that means just adding a new systimer entry? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
