Re: [PATCH 1/9] drm/mediatek: recalculate hdmi phy clock of MT2701 by querying hardware

[Matthias Brugger]

On 04/01/2019 08:03, chunhui dai wrote:
> Recalculate the rate of this clock, by querying hardware.
> 
> Signed-off-by: chunhui dai <chunhui.dai@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 | 49 ++++++++++++++++++++++++++
>  drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c |  8 +++++
>  4 files changed, 61 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> index 4ef9c57..79e737d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> +++ b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> @@ -29,12 +29,11 @@ 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);
> +	void __iomem *reg = hdmi_phy->regs + offset;
>  
> -	return hdmi_phy->pll_rate;
> +	return readl(reg);
>  }
>  
>  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 f39b1fc..fdad8b1 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 fcc42dc..b5ed6b7 100644
> --- a/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> +++ b/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> @@ -153,6 +153,55 @@ 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 = out_rate * (val + 1) * 2;
> +	val = (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON2)
> +			& RG_HDMITX_TX_POSDIV_MASK) >> RG_HDMITX_TX_POSDIV;
> +	switch (val) {
> +	case 0x00:
> +		out_rate = out_rate;
> +		break;
> +	case 0x01:
> +		out_rate = out_rate / 2;
> +		break;
> +	case 0x02:
> +		out_rate = out_rate / 4;
> +		break;
> +	case 0x03:
> +		out_rate = out_rate / 8;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	if (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON2) & RG_HDMITX_EN_TX_POSDIV)

Is this path time critical? You are reading the same register twice instead of
saving the read in a local varibale.

Regards,
Matthias

> +		out_rate = out_rate / 5;
> +
> +	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 ed5916b..cb23c1e 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,
>