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Message-ID: <1553234563.21474.6.camel@mtksdaap41>
Subject: Re: [PATCH v6 1/8] drm/mediatek: recalculate hdmi phy clock of
 MT2701 by querying hardware
From:   CK Hu <ck.hu@mediatek.com>
To:     wangyan wang <wangyan.wang@mediatek.com>
CC:     Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        "Philipp Zabel" <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        "Daniel Vetter" <daniel@ffwll.ch>,
        chunhui dai <chunhui.dai@mediatek.com>,
        "Colin Ian King" <colin.king@canonical.com>,
        Sean Wang <sean.wang@mediatek.com>,
        "Ryder Lee" <ryder.lee@mediatek.com>, <linux-clk@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>,
        <dri-devel@lists.freedesktop.org>, <srv_heupstream@mediatek.com>
Date:   Fri, 22 Mar 2019 14:02:43 +0800
In-Reply-To: <1553138590.18216.26.camel@mtksdaap41>
References: <20190225020912.29120-1-wangyan.wang@mediatek.com>
         <20190225020912.29120-2-wangyan.wang@mediatek.com>
         <1551866854.1001.6.camel@mtksdaap41> <1553138590.18216.26.camel@mtksdaap41>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi, Wangyan:

On Thu, 2019-03-21 at 11:23 +0800, CK Hu wrote:
> Hi, Wangyan:
> 
> On Wed, 2019-03-06 at 18:07 +0800, CK Hu wrote:
> > Hi, Wangyan:
> > 
> > On Mon, 2019-02-25 at 10:09 +0800, wangyan wang wrote:
> > > From: chunhui dai <chunhui.dai@mediatek.com>
> > > 
> > > Recalculate the rate of this clock, by querying hardware.
> > > 
> > > Signed-off-by: chunhui dai <chunhui.dai@mediatek.com>
> > > Signed-off-by: wangyan wang <wangyan.wang@mediatek.com>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_hdmi_phy.c        |  7 ++----
> > >  drivers/gpu/drm/mediatek/mtk_hdmi_phy.h        |  3 +--
> > >  drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c | 35 ++++++++++++++++++++++++++
> > >  drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c |  8 ++++++
> > >  4 files changed, 46 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> > > index 4ef9c57ffd44..13c5e65b9ead 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> > > @@ -29,12 +29,9 @@ long mtk_hdmi_pll_round_rate(struct clk_hw *hw, unsigned long rate,
> > >  	return rate;
> > >  }
> > >  
> > > -unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > > -				       unsigned long parent_rate)
> > > +u32 mtk_hdmi_phy_read(struct mtk_hdmi_phy *hdmi_phy, u32 offset)
> > >  {
> > > -	struct mtk_hdmi_phy *hdmi_phy = to_mtk_hdmi_phy(hw);
> > > -
> > > -	return hdmi_phy->pll_rate;
> > > +	return readl(hdmi_phy->regs + offset);

Inside mtk_hdmi_pll_recalc_rate(), there is just one function, why not
directly call readl() in the caller function?

> > >  }
> > >  
> > >  void mtk_hdmi_phy_clear_bits(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h
> > > index f39b1fc66612..fdad8b17a915 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h
> > > +++ b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h
> > > @@ -41,6 +41,7 @@ struct mtk_hdmi_phy {
> > >  	unsigned int ibias_up;
> > >  };
> > >  
> > > +u32 mtk_hdmi_phy_read(struct mtk_hdmi_phy *hdmi_phy, u32 offset);
> > >  void mtk_hdmi_phy_clear_bits(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > >  			     u32 bits);
> > >  void mtk_hdmi_phy_set_bits(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > > @@ -50,8 +51,6 @@ void mtk_hdmi_phy_mask(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > >  struct mtk_hdmi_phy *to_mtk_hdmi_phy(struct clk_hw *hw);
> > >  long mtk_hdmi_pll_round_rate(struct clk_hw *hw, unsigned long rate,
> > >  			     unsigned long *parent_rate);
> > > -unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > > -				       unsigned long parent_rate);
> > >  
> > >  extern struct platform_driver mtk_hdmi_phy_driver;
> > >  extern struct mtk_hdmi_phy_conf mtk_hdmi_phy_8173_conf;
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> > > index fcc42dc6ea7f..b25c9dfc432a 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> > > @@ -153,6 +153,41 @@ static int mtk_hdmi_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> > >  			  RG_HDMITX_DRV_IBIAS_MASK);
> > >  	return 0;
> > >  }
> > > +static unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > > +				       unsigned long parent_rate)
> > > +{
> > > +	struct mtk_hdmi_phy *hdmi_phy = to_mtk_hdmi_phy(hw);
> > > +	unsigned long out_rate, val;
> > > +
> > > +	val = (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON6)
> > > +			& RG_HTPLL_PREDIV_MASK) >> RG_HTPLL_PREDIV;
> > > +	switch (val) {
> > > +	case 0x00:
> > > +		out_rate = parent_rate;
> > > +		break;
> > > +	case 0x01:
> > > +		out_rate = parent_rate / 2;
> > > +		break;
> > > +	default:
> > > +		out_rate = parent_rate / 4;
> > > +		break;
> > > +	}
> > > +
> > > +	val = (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON6)
> > > +			& RG_HTPLL_FBKDIV_MASK) >> RG_HTPLL_FBKDIV;
> > > +	out_rate *= (val + 1) * 2;
> > > +	val = (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON2)
> > > +			& RG_HDMITX_TX_POSDIV_MASK);
> > > +
> > > +	out_rate >>= (val >> RG_HDMITX_TX_POSDIV);
> > > +
> > > +	if (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON2) & RG_HDMITX_EN_TX_POSDIV)
> > > +		out_rate = out_rate / 5;
> > > +
> > 
> > All the register you read here is set in mtk_hdmi_pll_set_rate(), so I
> > think you could determine the out_rate in mtk_hdmi_pll_set_rate().
> 
> As offline discuss, you mention that when
> cat /sys/kernel/debug/ckl/clk_summary, mtk_hdmi_pll_recalc_rate() is
> called, so read register to get the real clock. The clk_summary call
> clk_core_get_rate() to get rate, and clk_core_get_rate() would check the
> flag CLK_GET_RATE_NOCACHE to call __clk_recalc_rates(), but mtk_hdmi_phy
> does not have this flag, so this function would not be called when
> clk_summary. So I still think you could determine the out_rate in
> mtk_hdmi_pll_set_rate().

As offline discuss, recalc_rate is defined as follow:

 * @recalc_rate	Recalculate the rate of this clock, by querying
hardware. The
 *		parent rate is an input parameter.  It is up to the caller to
 *		ensure that the prepare_mutex is held across this call.
 *		Returns the calculated rate.  Optional, but recommended - if
 *		this op is not set then clock rate will be initialized to 0.

So it looks that recalc_rate is expected to query hardware to get the
out_rate. So this implementation is OK.

> 
> Regards,
> CK
> 
> > 
> > Regards,
> > CK
> > 
> > > +	hdmi_phy->pll_rate = out_rate;

I think you don't need to assign hdmi_phy->pll_rate in MT2701 because
it's useless in MT2701.

Regards,
CK

> > > +
> > > +	return hdmi_phy->pll_rate;
> > > +}
> > >  
> > >  static const struct clk_ops mtk_hdmi_phy_pll_ops = {
> > >  	.prepare = mtk_hdmi_pll_prepare,
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c
> > > index ed5916b27658..cb23c1e4692a 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c
> > > @@ -285,6 +285,14 @@ static int mtk_hdmi_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> > >  	return 0;
> > >  }
> > >  
> > > +static unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > > +				       unsigned long parent_rate)
> > > +{
> > > +	struct mtk_hdmi_phy *hdmi_phy = to_mtk_hdmi_phy(hw);
> > > +
> > > +	return hdmi_phy->pll_rate;
> > > +}
> > > +
> > >  static const struct clk_ops mtk_hdmi_phy_pll_ops = {
> > >  	.prepare = mtk_hdmi_pll_prepare,
> > >  	.unprepare = mtk_hdmi_pll_unprepare,
> > 
>