Re: [PATCH v6 1/8] drm/mediatek: recalculate hdmi phy clock of MT2701 by querying hardware

[CK Hu]

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@xxxxxxxxxxxx>
> > 
> > Recalculate the rate of this clock, by querying hardware.
> > 
> > Signed-off-by: chunhui dai <chunhui.dai@xxxxxxxxxxxx>
> > Signed-off-by: wangyan wang <wangyan.wang@xxxxxxxxxxxx>
> > ---
> >  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);
> >  }
> >  
> >  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().

Regards,
CK

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