linux-kernel - Re: [PATCH v4 4/8] drm/msm/dsi: 14nm PHY: Get ref clock from the DT

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Message-ID: <154525873917.79149.9742850766307036349@swboyd.mtv.corp.google.com>
Date:   Wed, 19 Dec 2018 14:32:19 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        David Brown <david.brown@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Clark <robdclark@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Archit Taneja <architt@...eaurora.org>,
        Sean Paul <seanpaul@...omium.org>,
        Rajesh Yadav <ryadav@...eaurora.org>,
        Douglas Anderson <dianders@...omium.org>,
        Jeykumar Sankaran <jsanka@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/8] drm/msm/dsi: 14nm PHY: Get ref clock from the DT

Quoting Matthias Kaehlcke (2018-12-19 14:22:22)
> On Mon, Dec 10, 2018 at 07:51:19AM -0800, Stephen Boyd wrote:
> > Quoting Matthias Kaehlcke (2018-12-04 14:42:30)
> > > diff --git a/drivers/gpu/drm/msm/dsi/pll/dsi_pll_14nm.c b/drivers/gpu/drm/msm/dsi/pll/dsi_pll_14nm.c
> > > index 71fe60e5f01f1..032bf3e8614bd 100644
> > > --- a/drivers/gpu/drm/msm/dsi/pll/dsi_pll_14nm.c
> > > +++ b/drivers/gpu/drm/msm/dsi/pll/dsi_pll_14nm.c
> > > @@ -40,7 +40,6 @@
> > >  
> > >  #define NUM_PROVIDED_CLKS              2
> > >  
> > > -#define VCO_REF_CLK_RATE               19200000
> > >  #define VCO_MIN_RATE                   1300000000UL
> > >  #define VCO_MAX_RATE                   2600000000UL
> > >  
> > > @@ -139,6 +138,7 @@ struct dsi_pll_14nm {
> > >         /* protects REG_DSI_14nm_PHY_CMN_CLK_CFG0 register */
> > >         spinlock_t postdiv_lock;
> > >  
> > > +       struct clk *vco_ref_clk;
> > 
> > Is there any need to keep it in the struct? Or just get the clk, find
> > the rate, and then put the clk and call pll_14nm_postdiv_register()?
> 
> I suppose you mean passing the clock name to pll_14nm_register()?

Yes, whatever makes it possible to avoid storing the pointer in the
struct.

> 
> Is putting the clock really needed or preferable, or is it just fine
> to auto-put it when the device is deleted?

Up to you. If you don't have a need for the clk anymore it seems fine to
just put the clk and be done.