You mean the longhaul driver can change the frequency of the PCI
bus? Oh, that's a recipe for disaster...
No. Sorry. My English is bad. I mean changing CPU frequency.
No, it's a hack :)
Again :-)
No, this is not acceptable. What exactly do you want to do here? Make
sure the PCI drivers are not doing DMA when the longhaul driver wants to
change the pci bus speed?
I'm trying not to break DMA. Current version of longhaul (marked broken
in 2.6.16.2) simply clears bus master bit on every device.
Does it really save battery?
Yes. And CPU temperature is lower.
And what about PCI devices that always do DMA? (think USB controllers,
they can easily saturate the PCI bus all the time).
This is worst for SATA. USB (this is strange) seems to work correcly.
I know that this is 10% coverage, but it is better then nothing.
It is always possible to add support for longhaul to driver.
Why not just suspend all PCI devices make the bus change, and then
resume them? That would require no PCI core, or driver changes.
This was my first idea. But trust me in current kernel this is simply
worst idea.
greg k-h
Though currently in the driver, voltage scaling is missing,
so we never save any power, and just run at the maximum voltage
the whole time.
I added this to longhaul, but it only works on non EBGA CPU's.
EBGA CPU's (at least Nehemiah) seem to have voltage scaling
disabled.
It needs there to be no bus mastering occuring at the time
of a CPU speed transition. Though I'm unable to find the part that mentions
this in the specs I have right now.
Dave
"Once this is set, the processor will switch to the
value in [26:23] on the next AUTOHALT transition. The duration of the AUTOHALT
should be >=1ms to ensure the CPU's internal PLL is resynchronized. For
AUTOHALT, this means interrupts must be disabled except for the time tick,
which should be reset to >=1ms. Care must be taken to avoid other system events
that could interfere with this operation. A few examples are snooping, NMI,
INIT, SMI and FLUSH."
For CPU's with Longhaul MSR this time is equal to 200us.
Rafał
----------------------------------------------------------------------
PS. Fajny portal... >>> http://link.interia.pl/f196a
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
