Messages in this thread | | | Date | Thu, 3 Feb 2005 12:02:34 -0800 | From | Venkatesh Pallipadi <> | Subject | Re: i386 HPET code |
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On Thu, Feb 03, 2005 at 11:30:56AM -0800, john stultz wrote: > On Thu, 2005-02-03 at 06:28 -0800, Pallipadi, Venkatesh wrote: > > Can you check whether only the following change makes the problem go > > away. If yes, then it looks like a hardware issue. > > > > > hpet_writel(hpet_tick, HPET_T0_CMP); > > >+ hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */ > > > > > Yep. Adding only the second write seems to make the box boot. > > Since this isn't just affecting our hardware (see Andrew Walrond's > comment in the thread), would doing two writes like x86-64 does be > acceptable? >
Yes. As this is just the initialization code, I think adding second write is OK. But, I am not sure why two writes are required and will the two write be sufficient for all systems. I don't seem to remember anything about this in HPET specs. I will double check it.
Basically I am thinking of something like this will be a good generic solution in place of simple two writes.
for (i = 0 ; i <some number for max retries>; i++) { hpet_writel(hpet_tick, HPET_T0_CMP); if (hpet_tick == hpet_readl(hpet_tick, HPET_T0_CMP)) break; }
I think we can wait for result from Andrew's system and chose either one of the above approaches.
Thanks, Venki
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