On Fri, 5 Jul 2013, Jonas Jensen wrote: > On 4 July 2013 23:42, Thomas Gleixner <t...@linutronix.de> wrote: > > You just modify bits on the "cache" variable. though you are not > > caching it. As it seems to work it looks like this register simply can > > be written with constants. > > I agree, the global "cache" variable wasn't very good. The only good thing, > that > it eliminated all TIMER_CR reads in moxart_clkevt_next_event.
Well, you can use a global cache variable. But that wants to be implemented as a real cache, i.e. it always contains the current state of the register. cache = 0; cache |= T2_ENABLE; write(cache, CR); .... > Yes it could be written with constants, and it wouldn't be so bad, because in > this case so few need to be set. If more constants were set from init > the benefit > would be more clear. > > >> + timereg_cache = readl(base + TIMER_CR) | TIMEREG_CR_2_ENABLE; > > > > Why are you reading that back? You know excactly which of the timers > > you are using and none of those should be enabled before you reach > > that code. If it one of them is enabled by the boot loader you better > > disable it in this init function. > > Removed. All timers except TIMER2 should be disabled in init. > > > Now if you disable all of those timers and just use a known set, then > > you can do without a pseudo cache variable and just write constants > > into the control register, right ? > > Yes, please take a look at v6. You are still reading from the control register. What's wrong with: #define T1_ENABLE (TIMEREG_CR_2_ENABLE | TIMEREG_CR_1_ENABLE) #define T1_DISABLE (TIMEREG_CR_2_ENABLE) Because you need to preserve the CR2 enable bit so your clocksource does not get switched off. Then the set_mode/next_event functions simply do: write(T1_DISABLE) write(data) write(T1_ENABLE) Hmm? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/