Am Montag, den 26.05.2014, 16:36 +0530 schrieb Viresh Kumar: > On 26 May 2014 16:15, Lucas Stach <l.stach@xxxxxxxxxxxxxx> wrote: > > This driver handles the i.MX5 specific clock reparenting to be able to > > reprogramm the PLL. cpufreq-cpu0 can only change a postdivider of the > > PLL, which means we can't reach the exact OPP frequencies and can not > > profit from the additional power savings of a slower running PLL. > > > > Also without reprogramming the PLL we could possibly not scale to the > > highest OPPs if the bootloader left the PLL at a slower rate. This is > > the case for many i.MX53 boards, as the CPU regulator normally does > > start up with the voltage required for 800MHz operation. If the > > bootloader decides to not touch the regulator and set the PLL to 800MHz > > the 1GHz and 1.2GHz operating points won't be useable. > > Almost all users of cpufreq-cpu0 has such situations and they have > written a clock-driver for "cpu clock" to get this fixed. And they handle > all this PLL stuff in clk_set_rate() for this new clock.. > > I still couldn't find anything so special here that can't be fixed this way. > There is no point adding and maintaining a cpufreq driver if we can > use cpufreq-cpu0. Ok I can push down the clock handling into the imx5 clk driver. This leaves two more differences between imx5-cpufreq and cpufreq-cpu0: 1. Disabling of OPPs that could not be supported by the connected regulator. I think this part can easily be made generic and pushed into cpu0, as it should be beneficial to other SoCs too. 2. Usage of a fixed max voltage, rather than a voltage-tolerance. i.MX5 has a fixed maximum voltage, which is valid across all operating points. I'm really opposed to using a tolerance value, where we instead could have a well defined range. So for merging imx5-cpufreq into cpufreq-cpu0 this driver really need to handle this case. Does adding a separate property for this, while keeping the voltage-tolerance for the existing users, sound like a change you would accept? Regards, Lucas -- Pengutronix e.K. | Lucas Stach | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
