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: <200406022039.07672.toojays@toojays.net> References: <200405302331.35357.toojays@toojays.net> <200405311807.59356.toojays@toojays.net> <1086047232.1930.74.camel@gaston> <200406022039.07672.toojays@toojays.net> Content-Type: text/plain Message-Id: <1086301583.1838.39.camel@gaston> Mime-Version: 1.0 Date: Fri, 04 Jun 2004 08:26:24 +1000 Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: On Wed, 2004-06-02 at 21:08, John Steele Scott wrote: > I don't know much about manipulating the GPIO stuff, but I guess I will learn > it sometime in the next few days and hopefully get to a fully working patch. GPIO just means "general purpose IO", it's just IO bits hanging out of the KeyLargo chipsets and connected to various things on the motherboard, in that case, one is connected to the power supply controller to control the power to the CPU. Look at the cpufreq code for gpios_set_cpuspeed(), it's used on models were both the clock frequency and the voltage are controller by GPIOs, keep the voltage part. Remember to ramp up the voltage before setting the frequency to high, and ramp it down after setting the frequency to low. Ben. ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/