Re: [PATCH v2 12/15] clk: sunxi-ng: a64: Add min and max rate for PLL_MIPI

[Maxime Ripard]

On Thu, Oct 25, 2018 at 09:21:31PM +0530, Jagan Teki wrote:
> On Wed, Oct 24, 2018 at 11:43 PM Maxime Ripard
> <maxime.ripard@xxxxxxxxxxx> wrote:
> >
> > On Tue, Oct 23, 2018 at 09:20:32PM +0530, Jagan Teki wrote:
> > > A64 manual say PLL_MIPI rates are 500MHz to 1.4GHz, but
> > > using minimum 500MHz can't release the clock and which
> > > is not working.
> > >
> > > So use working minimum rate as 300MHz which is tested on
> > > Bananapi DSI panel.
> >
> > I'm not quite sure what you mean by that. What do you mean by "500MHz
> > can't release the clock"? Why would 300MHz work better then? Should be
> > avoid reaching 500MHz if it's a frequency in the valid range?
> 
> PLL_MIPI can't be work with existing nkm where rate set to 270MHz
> (from PLL_VIDEO)
> /*** round rate call in ccu_nkm.c */
> [    2.408356] round: rate = 118800000
> [    2.408359] round: parent_rate = 158740688
> [    2.408417] round: rate = 148500000
> [    2.408420] round: parent_rate = 158740688
> [    2.408439] round: rate = 178200000
> [    2.408441] round: parent_rate = 158740688
> [    2.408460] round: rate = 205615384
> [    2.408462] round: parent_rate = 158740688
> [    2.408481] round: rate = 237600000
> [    2.408483] round: parent_rate = 158740688
> [    2.408502] round: rate = 270000000
> [    2.408504] round: parent_rate = 158740688
> [    2.408523] round: rate = 118800000
> [    2.408525] round: parent_rate = 158740560
> [    2.408544] round: rate = 148500000
> [    2.408546] round: parent_rate = 158740560
> [    2.408565] round: rate = 178200000
> [    2.408567] round: parent_rate = 158740560
> [    2.408586] round: rate = 205615384
> [    2.408588] round: parent_rate = 158740560
> [    2.408607] round: rate = 237600000
> [    2.408609] round: parent_rate = 158740560
> [    2.408627] round: rate = 270000000
> [    2.408630] round: parent_rate = 158740560
> [    2.408648] round: rate = 270000000
> [    2.408651] round: parent_rate = 158740640
> [    2.408670] round: rate = 270000000
> [    2.408672] round: parent_rate = 158740704
> 
> /** set rate call in ccu_nkm **/
> [    2.408685] set: rate = 270000000
> [    2.408688] set: parent_rate = 297000000
> 
> By using min and max rate as per A64 manual page 94 range of PLL can
> be 500MHz~1.4GHz getting 1,2,1 nkm dividers which can't be work.
> [    2.423589] sun4i_dclk_round_rate: min_div = 4 max_div = 127, rate = 55000000
> [    2.423643] ideal = 220000000, rounded = 0
> [    2.423647] ideal = 275000000, rounded = 0
> [    2.423651] ideal = 330000000, rounded = 0
> [    2.423692] ideal = 385000000, rounded = 384000000
> [    2.423732] ideal = 440000000, rounded = 440000000
> [    2.423736] sun4i_dclk_round_rate: div = 8 rate = 55000000
> [    2.423740] sun4i_dclk_round_rate: min_div = 4 max_div = 127, rate = 55000000
> [    2.423744] ideal = 220000000, rounded = 0
> [    2.423748] ideal = 275000000, rounded = 0
> [    2.423751] ideal = 330000000, rounded = 0
> [    2.423791] ideal = 385000000, rounded = 384000000
> [    2.423831] ideal = 440000000, rounded = 440000000
> [    2.423834] sun4i_dclk_round_rate: div = 8 rate = 55000000
> [    2.423957] sun4i_dclk_recalc_rate: val = 1, rate = 440000000
> [    2.423961] sun4i_dclk_recalc_rate: val = 1, rate = 440000000
> [    2.424378] ccu_nkm_set_rate: rate = 440000000, parent_rate = 220000000
> [    2.424381] ccu_nkm_set_rate: _nkm.n = 1
> [    2.424383] ccu_nkm_set_rate: _nkm.k = 2
> [    2.424385] ccu_nkm_set_rate: _nkm.m = 1
> [    2.424725] sun4i_dclk_set_rate div 8
> [    2.424732] sun4i_dclk_recalc_rate: val = 8, rate = 55000000
> [    2.561271] usb 3-1: new high-speed USB device number 2 using ehci-platform
> [    2.718486] hub 3-1:1.0: USB hub found
> [    2.718606] hub 3-1:1.0: 4 ports detected
> [    3.437263] ------------[ cut here ]------------
> [    3.437270] [CRTC:36:crtc-0] vblank wait timed out
> 
> So, lowering the min rate by 300MHz seems working with bounded nkm
> dividers 5, 2, 9. Tested on two different panels.
> 
> [    2.415773] [drm] No driver support for vblank timestamp query.
> [    2.424116] sun4i_dclk_round_rate: min_div = 4 max_div = 127, rate = 55000000
> [    2.424172] ideal = 220000000, rounded = 0
> [    2.424176] ideal = 275000000, rounded = 0
> [    2.424194] ccu_nkm_round_rate: rate = 330000000
> [    2.424197] ideal = 330000000, rounded = 330000000
> [    2.424201] sun4i_dclk_round_rate: div = 6 rate = 55000000
> [    2.424205] sun4i_dclk_round_rate: min_div = 4 max_div = 127, rate = 55000000
> [    2.424209] ideal = 220000000, rounded = 0
> [    2.424213] ideal = 275000000, rounded = 0
> [    2.424230] ccu_nkm_round_rate: rate = 330000000
> [    2.424233] ideal = 330000000, rounded = 330000000
> [    2.424236] sun4i_dclk_round_rate: div = 6 rate = 55000000
> [    2.424253] ccu_nkm_round_rate: rate = 330000000
> [    2.424270] ccu_nkm_round_rate: rate = 330000000
> [    2.424278] sun4i_dclk_recalc_rate: val = 1, rate = 330000000
> [    2.424281] sun4i_dclk_recalc_rate: val = 1, rate = 330000000
> [    2.424306] ccu_nkm_set_rate: rate = 330000000, parent_rate = 297000000
> [    2.424309] ccu_nkm_set_rate: _nkm.n = 5
> [    2.424311] ccu_nkm_set_rate: _nkm.k = 2
> [    2.424313] ccu_nkm_set_rate: _nkm.m = 9
> [    2.424661] sun4i_dclk_set_rate div 6
> [    2.424668] sun4i_dclk_recalc_rate: val = 6, rate = 55000000
> 
> Note: BPI-M64-bsp is setting the rate directly to 180MHz with 297MHz
> parent with resulting dividers as 1, 2, 5. ans we can't produce this
> 180MHz rate with dclk_round_rate and ccu_nkm.

I'm still not quite sure what you mean by "500MHz can't release the
clock".

From what you're saying, this seems to be related to the boundaries of
the dividers rather than the rate itself.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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