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

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Date:	Mon, 23 Nov 2015 17:20:21 +0800
From:	hl <hl@...k-chips.com>
To:	Heiko Stuebner <heiko@...ech.de>
CC:	dianders@...omium.org, mturquette@...libre.com,
	myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
	linux-clk@...r.kernel.org, sboyd@...eaurora.org,
	dbasehore@...omium.org, linux-rockchip@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] clk: rockchip: dmc: support rk3399 dmc clock driver

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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