Re: [PATCH] clk: rockchip: rk3399: add pll up and down when change pll freq

[Doug Anderson]

Xing,

On Tue, Aug 2, 2016 at 6:13 AM, Xing Zheng <zhengxing@xxxxxxxxxxxxxx> wrote:
> From: Elaine Zhang <zhangqing@xxxxxxxxxxxxxx>
>
> The suggestion that is from IC designer, the correct pll sequence setting
> should be like these:
> ----
>   set pll to slow mode or other plls
>   set pll down
>   set pll params
>   set pll up
>   wait pll lock status
>   set pll to normal mode
> ----
>
> Hence, there are potential risks that we need to fix:
> rockchip_rk3399_wait_pll_lock - timeout waiting for pll to lock
> rockchip_rk3399_pll_set_params - pll update unsucessful, trying to restore old params

I still don't understand how that groks with the statement in the TRM:

> In most cases the PLL programming can be changed on-the-fly and the PLL will simply slew to the new frequency

That makes it sound like these PLLs are super great at dynamic updates.