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. 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. Cheers Jon -- 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
