[U-Boot] [linux-sunxi] Re: [PATCH] sunxi: set up PLL1 on sun6i+ without use dividers

[Ondřej Jirman]

icenowy at aosc.io píše v Po 10. 04. 2017 v 18:15 +0800:
> 在 2017-04-10 18:06，Ondřej Jirman 写道：
> > Hi Maxime,
> > 
> > Maxime Ripard píše v Po 10. 04. 2017 v 08:59 +0200:
> > > On Mon, Apr 10, 2017 at 12:19:41AM +0800, Icenowy Zheng wrote:
> > > > According to the researching result of Ondrej Jirman, the factor M of
> > > > PLL1 shouldn't be used and the factor P should be used only if the
> > > > intended frequency is lower than 288MHz. This is proven by the
> > > > clk-sun8iw7_tbl.c in the BSP source code -- in there the M value is
> > > > always 0 and the maximum frequency that P is not 0 is 224MHz.
> > > > 
> > > > As P is ignored on sun6i, it's not currently used. This patch removed
> > > > the usage of M.
> > > > 
> > > > This patch is an original work by Ondrej Jirman, however, he didn't add
> > > > a Signed-off-by tag here to his commit. So I take this code and added my
> > > > Signed-off-by.
> > > > 
> > > > Signed-off-by: Icenowy Zheng <icenowy at aosc.io>
> > > > ---
> > > > 
> > > > This is a critical patch, and should be added to 2017.05.
> > > > 
> > > > It has been verified by the Armbian.
> > > 
> > > This doesn't mean anything. How has this been verified?
> > 
> > We already discussed this here: https://patchwork.kernel.org/patch/9446
> > 365/
> 
> P.S. as Chen-Yu dig out, it's not the correct work to restrict factors,
> but we need to gate the PLL_CPUX when adjusting. (Of course the mux 
> should
> also be switched to osc24M when PLL_CPUX is gated)
> 
> I tried this on your h3-firmware code, and it succeeded with even P 
> overused
> (for any frequency) (and M is also free in this situation).

Interesting, I was only switching the source of the CPUX clock, and not
gating the CPUX_PLL for the test. I guess the kernel still doesn't gate
CPUX_PLL, so this whole situation should be fixed by adding the gating
of PLL during the chnage and that would be it?

Sounds like the cleanest solution so far.

regards,
  o.j.

> > 
> > regards,
> >   o.j.
> > 
> > > Maxime
> > > 
> > > --
> > > Maxime Ripard, Free Electrons
> > > Embedded Linux and Kernel engineering
> > > http://free-electrons.com
> > > 
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