Messages in this thread | | | Date | Tue, 18 May 2010 09:38:32 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH 7/8] x86/mrst: add vrtc driver which serves as a wall clock device |
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On Tue, 18 May 2010, Feng Tang wrote: > Hi Thomas, > > > On Mon, 17 May 2010 17:15:55 +0800 > Thomas Gleixner <tglx@linutronix.de> wrote: > > > > > > > > Actually when to init the vrtc register is a big problem for me, > > > vrtc need be inited before timekeeping_init(), and I thought better > > > to put it somewhere in setup_arch(), as it is architecture > > > specific, and ioremap is not working at that time. Also that's the > > > reason I created a new wallclock_init func for x86_platforms, I > > > could not find a better way to do the vrtc init. > > > > There is no particular reason why we need to read it in > > timekeeping_init(). Nothing in the kernel needs the correct wall time > > at that point. So we can safely move the setting of xtime to rtc wall > > clock time to a separate timekeeping_late_init() function. > > > > John ??? > > > Yeah, good suggestion, if xtime init is moved to a later time in kernel > init flow, then vrtc's init function can be set a arch_initcall()
John was away yesterday, so we have to wait for his answer, but I don't expect a nono from him.
> > > > > + lock_cmos_prefix(reg); > > > > > > > > This lock_cmos magic should just die. I have no idea why > > > > something wants or wanted to access the RTC from an NMI. > > > > > > I will try to reuse the rtc_lock defined in rtc.c whose get/set_time > > > service won't be called with vrtc's at the same time. > > > > Please don't create artifical dependencies. Use a separate vrtc_lock > > to serialize the access to vrtc. > I just checked the code, when wall clock's get/set_time service is called, > it is always protected by rtc_lock(code in arch/x86/kernel/rtc.c), then > no need to add the lock for each individual register read/write operation.
Grr. Yes, missed that the code is called under rtc_lock already. So you can drop the locking in your code completely.
Thanks,
tglx
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