On Tue, 9 Aug 2016 18:02:47 +0800 Chen-Yu Tsai <[email protected]> wrote:
> > The 'parent's of the bus gates are of no interest. > > They are supposed to be (no clear documentation) apb1, apb2, ahb1 and > > ahb2, but, as you well noticed in the patch 5/7, these clocks are fixed > > and have no gate. Some of them are parents of real clocks, but they > > don't bring anything to the bus gates of the other clocks. > > Yes they are. Some devices, such as UARTs and I2C controllers, need > to get the clock rate of the gate and calculate the proper internal > divider. You are right, the clocks of some subsystems have only a gate, but these are exceptions. Look at an ordinary clock, say the mmc0 of the H3. There is a "bus" gate (see below) in the CCU register 0x60, bit 8, and the "clock" gate in the CCU register 0x88, bit 31. The 'simple-gates' says that the "bus gate" is child of ahb1 (in all sunxi versions, the one prior to 'simple-gate', in the 'simple-gate', in 'sunxi-ng', and now in André's patch). But, where do you see a hardware relation between the mmc0 clock and the ahb1 clock? > > As I wrote previously, the simplest is to ungate/gate the clocks in > > both the bus and clock registers on clk_prepare/unprepare. > > Then, your 'multi-bus-gates' would be simply a generic 'multi-gates'. > > This is somewhat misleading. What "clock" registers are you referring > to? There are no "bus" registers. The reason we call them "bus clock > gates" is because they are mashed together, instead of having clearly > separated registers for each AHB/APB bus. > > And if you want just a generic clock gates driver, we already have > the "simple-gates" driver. Maybe I used the wrong words. The "clock" register is the one which defines the parameters of the clock (parents, mul/div factors, gate). For the H3 mmc0, it is the CCU register 0x60. The "bus" register is one of the so-called "Bus Clock Gating Register"s. For the H3 mmc0, it is the CCU register 0x88. -- Ken ar c'hentañ | ** Breizh ha Linux atav! ** Jef | http://moinejf.free.fr/
