From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: nearly-working support for cpufreq on 2004 iBook G4 with 7447A cpu From: Benjamin Herrenschmidt To: John Steele Scott Cc: linuxppc-dev list , Christiaan Welvaart In-Reply-To: <200405311807.59356.toojays@toojays.net> References: <200405302331.35357.toojays@toojays.net> <200405311003.21439.toojays@toojays.net> <1085975390.1930.31.camel@gaston> <200405311807.59356.toojays@toojays.net> Content-Type: text/plain Message-Id: <1086047232.1930.74.camel@gaston> Mime-Version: 1.0 Date: Tue, 01 Jun 2004 09:47:12 +1000 Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Oh, and when switching to high speed, think about tweaking the voltage too. I don't know if it's high or low when setting the GPIO bit, you may want to check out OF code, it certainly have methods for that. Or you can read the voltage value back from the adt themometer chip I think, as it does voltage control. (see cpu-vcore-select GPIO) I suspect that the machine boots at low speed & low voltage. You should either set it to high speed in pmac_feature (before bogomips calculation) or assume it has booted low speed in your driver. You need to ramp up voltage & wait before swiotching to high speed and ramp down voltage after switching to low speed. The delay is unknown, I suppose 100ms should be plenty enough though (probably even too much). Ben. ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/