Re: [PATCH 1/2] clk: rockchip: dmc: support rk3399 dmc clock driver

[hl]

Hi Heiko,

On 22/11/15 02:30, Heiko Stuebner wrote:
> Hi Lin,
>
> Am Freitag, 20. November 2015, 09:37:15 schrieb hl:
> > On 20/11/15 05:47, Heiko Stuebner wrote:
> > > Hi Lin,
> > >
> > > Am Donnerstag, 19. November 2015, 18:21:10 schrieb Lin Huang:
> > > > support rk3399 dmc clock driver. Note, ddr set rate function will
> > > > use dcf controller which run in ATF, it need to fishish it when rk3399
> > > > arm trust firmware ready.
> > > this unfinalized state is slightly unfortunate and I think this code will
> > > need to wait until CRU and DDRC specs are available.
> > >
> > > Because this is clearly part of the CRU (labeled CRU_CLKSEL6_CON etc)
> > > so shouldn't be a separate driver at all and also what your driver currently
> > > only does can still simply be described in the regular scheme as part of
> > > a full clock driver like
> > >
> > > PNAME(mux_ddrc_p) = { "pll_dpll", "pll_gpll", "pll_alpll", "pll_abpll" };
> > > COMPOSITE_NOGATE(0, "ddrc", mux_ddrc_p, 0,
> > > 					RK3399_CLKSEL_CON(6), 4, 2, MFLAGS, 0, 3,
> > > 					DFLAGS | CLK_DIVIDER_POWER_OF_TWO),
> > >
> > > So the code needs to actually demonstrate why a separate clock type is
> > > really necessary.
> > >
> > > I do understand that we will probably need a special way to talk to this
> > > dcf controller but seeing how this interaction will work is really a
> > > prequisite to finding a correct solution.
> >       if we can use common clock driver, i can put the dfi controller as
> > a  independent driver
> >       into devfreq,  this is the best way. But how do we separate the ddr
> > clk_set_rate() ,
> >       so we can manipulate dcf controller(actually, we use SMC handle dcf
> > controller in arm trust firmware ),
> >       i check clock driver code, it seem there is not way to do that for now.
> the core problem I have right now is, that I don't understand how the
> interaction with the dfi controller works at all :-) .
>
> One thing that might work, is that your dfi-driver takes the ddrc-clock
> from the clock controller and then registers a clock notifier to get
> notified before and after the clock-rate changes. But that depends as
> stated above on how the dfi-controller needs to be handled.
>
> For example the current armclk-handling uses a clock notifier around the
> actual rate change ... so you could use that as inspiration.
    Thank you for your inspiration. I think i can handle ddrc clk like 
the armclk.
    About the dfi, it will monitor ddr utilization, according this 
result to do
    ddr frequency scaling. I think i can implement a dfi drvier, and 
register it to devfreq,
    then call the dmc_set_rate fucntion in the dfi drvier, meanwhile i 
will implement a ddrc clk driver
    like the armclk, implement set rate funciton, and call the 
dcf(implement in ATF) in this function.
> Heiko

--
Lin Huang


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