Currently, whenever we idle a device _idle_sysc() is called and writes to the devices SYSCONFIG register to set the idle mode. A lot devices are using the smart-idle mode and so the write to the SYSCONFIG register is programming the same value that is already stored in the register. Writes to the devices SYSCONFIG register can be slow, for example, writing to the DMTIMER SYSCONFIG register takes 3 interface clock cycles and 3 functional clock cycles. If the DMTIMER is using the slow 32kHz functional clock this can take ~100us. Furthermore, during boot on an OMAP4430 panda board, I see that there are 100 calls to _idle_sysc(), however, only 3 out of the 100 calls actually write the SYSCONFIG register with a new value. Therefore, to avoid unnecessary writes to device SYSCONFIG registers when idling the device, only write the value if the value has changed. It should be safe to do this on idle as the context of the register will never be lost while the device is active. Verified that suspend, CORE off and retention states are working with this change on OMAP3430 Beagle board. Signed-off-by: Jon Hunter <jon-hunter@xxxxxx> --- arch/arm/mach-omap2/omap_hwmod.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c index b969ab1..962773b 100644 --- a/arch/arm/mach-omap2/omap_hwmod.c +++ b/arch/arm/mach-omap2/omap_hwmod.c @@ -1389,6 +1389,10 @@ static void _idle_sysc(struct omap_hwmod *oh) if ((sf & SYSC_HAS_SIDLEMODE) && !(oh->flags & HWMOD_SWSUP_SIDLE)) _enable_wakeup(oh, &v); + /* If the cached value is the same as the new value, skip the write */ + if (oh->_sysc_cache == v) + return; + _write_sysconfig(v, oh); } -- 1.7.9.5 -- 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
