Messages in this thread | | | Date | Sat, 15 May 2010 09:29:08 -0700 | From | Jesse Barnes <> | Subject | Re: [PATCH 2/2] x86 platform driver: intelligent power sharing driver |
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On Sat, 15 May 2010 01:54:56 -0700 Andy Isaacson <adi@hexapodia.org> wrote:
> On Mon, May 10, 2010 at 10:00:46PM -0400, Andrew Morton wrote: > > > + int i; > > > + u16 avg; > > > + > > > + for (i = 0; i < IPS_SAMPLE_COUNT; i++) > > > + total += (u64)(array[i] * 100); > > > > Actually, that does work. Somehow the compiler will promote > > array[i] to u64 _before_ doing the multiplication. I think. > > Still, it looks like a deliberate attempt to trick the compiler > > into doing a multiplicative overflow ;) > > It seems to promote to int, probably due to the implicit type of > "100". Aind since array is u16, * 100 can't overflow int. So yes, > it's safe, but it does catch the eye as potentially unsafe.
Newest version uses do_div, I think I got it right there.
> > > > + cur_seqno = (thm_readl(THM_ITV) & > > > ITV_ME_SEQNO_MASK) >> > > > + ITV_ME_SEQNO_SHIFT; > > > + if (cur_seqno == last_seqno && > > > + time_after(jiffies, seqno_timestamp + HZ)) { > > > + dev_warn(&ips->dev->dev, "ME failed to > > > update for more than 1s, likely hung\n"); > > > + } else { > > > + seqno_timestamp = get_jiffies_64(); > > > + last_seqno = cur_seqno; > > > + } > > > + > > > + last_msecs = jiffies_to_msecs(jiffies); > > Once it triggers, this will print the "likely hung" message every > second until the end of time, won't it?
The ME should eventually reset itself, but in the interim we can't trust its data. So I should add some better handling for that case (e.g. disable turbo); however this was more of a debug feature for early MEs, I don't think it'll happen on production hardware.
Jesse
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