Re: [PATCH v6 4/7] clk: mediatek: Add MT2701 clock support

[James Liao <jamesjj.liao-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>]

Hi Mike,

Sorry to use this old email to ask questions. Do you have any concern to
apply this patch series into next version of kernel? Or do you really
need a new patch series with less CLK_OF_DECLARE()?


Best regards,

James


On Thu, 2016-02-25 at 14:24 +0800, James Liao wrote:
> Hi Mike,
> 
> On Wed, 2016-02-24 at 13:25 -0800, Michael Turquette wrote:
> > Hi James,
> > 
> > Quoting James Liao (2016-02-15 01:19:42)
> > > Hi Mike,
> > > 
> > > On Wed, 2016-02-10 at 12:08 -0800, Michael Turquette wrote:
> > > > Quoting James Liao (2016-02-05 01:37:27)
> > > > > +CLK_OF_DECLARE(mtk_topckgen, "mediatek,mt2701-topckgen", mtk_topckgen_init);
> > > > > +CLK_OF_DECLARE(mtk_infrasys, "mediatek,mt2701-infracfg", mtk_infrasys_init);
> > > > > +CLK_OF_DECLARE(mtk_pericfg, "mediatek,mt2701-pericfg", mtk_pericfg_init);
> > > > > +CLK_OF_DECLARE(mtk_mmsys, "mediatek,mt2701-mmsys", mtk_mmsys_init);
> > > > > +CLK_OF_DECLARE(mtk_imgsys, "mediatek,mt2701-imgsys", mtk_imgsys_init);
> > > > > +CLK_OF_DECLARE(mtk_vdecsys, "mediatek,mt2701-vdecsys", mtk_vdecsys_init);
> > > > > +CLK_OF_DECLARE(mtk_hifsys, "mediatek,mt2701-hifsys", mtk_hifsys_init);
> > > > > +CLK_OF_DECLARE(mtk_ethsys, "mediatek,mt2701-ethsys", mtk_ethsys_init);
> > > > > +CLK_OF_DECLARE(mtk_bdpsys, "mediatek,mt2701-bdpsys", mtk_bdpsys_init);
> > > > > +CLK_OF_DECLARE(mtk_apmixedsys, "mediatek,mt2701-apmixedsys",
> > > > 
> > > > :-/
> > > > 
> > > > This is way too much CLK_OF_DECLARE and not enough Linux Driver Model.
> > > > 
> > > > I understand that some platforms really must initialize some clocks very
> > > > early, but can we please separate those into one table and call
> > > > CLK_OF_DECLARE on only that set, and then register the rest through a
> > > > platform_driver later on?
> > > 
> > > I know CLK_OF_DECLARE is much earlier than platform_driver, so it can
> > > ensure all drivers lookup their clocks successfully during
> > > platform_driver probe. Is there anything different to init these clock
> > > providers in CLK_OF_DECLARE and platform_driver?
> > 
> > This a common pattern we're seeing right now. Joachim did a nice job of
> > supporting early clocks with CLK_OF_DECLARE, and also using a proper
> > driver in his lpc18xx implementation:
> > 
> > http://marc.info/?l=devicetree&m=145618160610001
> 
> Do you mean we should keep most clock init in platform_driver_probe and
> use CLK_OF_DECLARE for some early clocks only?
> 
> Using CLK_OF_DECLARE() for all clock providers is convenient. The
> convenience includes coding structure and driver init order. The coding
> structure means we can use a consistency way to add clock providers, so
> we can reduce errors and apply code generator on clock drivers.
> 
> The driver init order is another issue. In lpc18xx driver you mentioned
> in [1], it uses ERR_PTR(-EPROBE_DEFER) to be the place holder for
> non-early clocks in arch_init (CLK_OF_DECLARE), and then register early
> and non-early clocks again in module_init. The EPROBE_DEFER place holder
> is an interesting idea to resolve init order issue. But to register
> clocks twice on the same clock provider seems not a good idea, although
> it can still work in current CCF implementation.
> 
> Is it important to move clock init into platform_driver? If not, I
> prefer to keep current implementation on MT2701, and look for a better
> way to init clocks in platform_driver in new SoCs.
> 
> 
> [1] http://marc.info/?l=devicetree&m=145618160610001
> 
> 


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