* Matthijs van Duin <matthijsvanduin@xxxxxxxxx> [151112 01:21]: > On 11 November 2015 at 18:40, Tony Lindgren <tony@xxxxxxxxxxx> wrote: > > Well we do first try to set the rate using the divider only at least for > > drivers/clk/ti/fapll.c used on dm816x. I'm thinking about doing a similar > > driver for the dm814x adpll where we have a PLL and separate output clocks > > in a single driver as the PLL and output control registers are all mixed in. > > Well the output control *is* part of the PLL block. More importantly, > due to the constraints of DPLL-LJ you may need to consider the > postdivider and PLL config together to produce the desired output > frequency. Yup. > Note BTW that afaik exactly the same two DPLL types are used in nearly > all TI SoCs (with exception of DM816x, and some enhancements have been > made in the latest SoCs), but since the PLLs themselves only have > wires sticking out, the register interface can vary significantly > between devices. Most of them also wrap a layer of abstraction around > them, while it seems the DM814x just directly wired all available > signals into registers, no added sugar. > > Another difference is that normally nearly all DPLLs are DPLL-S (aka > "type A") and often only one is -LJ (aka "type B"), while the > situation is reversed on the DM814x which has only one instance of > DPLL-S and 12 instances of DPLL-LJ. Also unusual is that none have > more than one output divider (no HSDIVIDER blocks present) and only > two (HDMI and USB) make direct use of the undivided dco clock. This > means that, with those two exceptions, you do have complete freedom in > configuring the PLL for the needs of its single output clock. OK > It does however also mean you can't really escape dealing with the > fussiness of DPLL-LJ like you can on other devices (e.g. the am335x > has only one, which is configured correctly by ROM and can't be > reconfigured without breaking USB.) Does the old TI kernel tree driver correctly handle that? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
