linux-kernel - Re: [PATCH 12/15] drm/sun4i: Add support for second clock parent to DW HDMI PHY clk driver

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Date:   Mon, 21 May 2018 10:12:53 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Jernej Skrabec <jernej.skrabec@...l.net>
Cc:     wens@...e.org, robh+dt@...nel.org, mark.rutland@....com,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH 12/15] drm/sun4i: Add support for second clock parent to
 DW HDMI PHY clk driver

On Sat, May 19, 2018 at 08:31:24PM +0200, Jernej Skrabec wrote:
> Expand HDMI PHY clock driver to support second clock parent.
> 
> Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> ---
>  drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h      |  6 +-
>  drivers/gpu/drm/sun4i/sun8i_hdmi_phy.c     | 29 ++++++-
>  drivers/gpu/drm/sun4i/sun8i_hdmi_phy_clk.c | 90 ++++++++++++++++------
>  3 files changed, 98 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h
> index 801a17222762..aadbe0a10b0c 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h
> +++ b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h
> @@ -98,7 +98,8 @@
>  #define SUN8I_HDMI_PHY_PLL_CFG1_LDO2_EN		BIT(29)
>  #define SUN8I_HDMI_PHY_PLL_CFG1_LDO1_EN		BIT(28)
>  #define SUN8I_HDMI_PHY_PLL_CFG1_HV_IS_33	BIT(27)
> -#define SUN8I_HDMI_PHY_PLL_CFG1_CKIN_SEL	BIT(26)
> +#define SUN8I_HDMI_PHY_PLL_CFG1_CKIN_SEL_MSK	BIT(26)
> +#define SUN8I_HDMI_PHY_PLL_CFG1_CKIN_SEL_SHIFT	26
>  #define SUN8I_HDMI_PHY_PLL_CFG1_PLLEN		BIT(25)
>  #define SUN8I_HDMI_PHY_PLL_CFG1_LDO_VSET(x)	((x) << 22)
>  #define SUN8I_HDMI_PHY_PLL_CFG1_UNKNOWN(x)	((x) << 20)
> @@ -190,6 +191,7 @@ void sun8i_hdmi_phy_remove(struct sun8i_dw_hdmi *hdmi);
>  void sun8i_hdmi_phy_init(struct sun8i_hdmi_phy *phy);
>  const struct dw_hdmi_phy_ops *sun8i_hdmi_phy_get_ops(void);
>  
> -int sun8i_phy_clk_create(struct sun8i_hdmi_phy *phy, struct device *dev);
> +int sun8i_phy_clk_create(struct sun8i_hdmi_phy *phy, struct device *dev,
> +			 bool second_parent);
>  
>  #endif /* _SUN8I_DW_HDMI_H_ */
> diff --git a/drivers/gpu/drm/sun4i/sun8i_hdmi_phy.c b/drivers/gpu/drm/sun4i/sun8i_hdmi_phy.c
> index deba47ed69d8..7a911f0a3ae3 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_hdmi_phy.c
> +++ b/drivers/gpu/drm/sun4i/sun8i_hdmi_phy.c
> @@ -183,7 +183,13 @@ static int sun8i_hdmi_phy_config_h3(struct dw_hdmi *hdmi,
>  	regmap_update_bits(phy->regs, SUN8I_HDMI_PHY_ANA_CFG1_REG,
>  			   SUN8I_HDMI_PHY_ANA_CFG1_TXEN_MASK, 0);
>  
> -	regmap_write(phy->regs, SUN8I_HDMI_PHY_PLL_CFG1_REG, pll_cfg1_init);
> +	/*
> +	 * NOTE: We have to be careful not to overwrite PHY parent
> +	 * clock selection bit and clock divider.
> +	 */
> +	regmap_update_bits(phy->regs, SUN8I_HDMI_PHY_PLL_CFG1_REG,
> +			   ~SUN8I_HDMI_PHY_PLL_CFG1_CKIN_SEL_MSK,
> +			   pll_cfg1_init);

It feels like it belongs in a separate patch.

>  	regmap_update_bits(phy->regs, SUN8I_HDMI_PHY_PLL_CFG2_REG,
>  			   (u32)~SUN8I_HDMI_PHY_PLL_CFG2_PREDIV_MSK,
>  			   pll_cfg2_init);
> @@ -352,6 +358,10 @@ static void sun8i_hdmi_phy_init_h3(struct sun8i_hdmi_phy *phy)
>  			   SUN8I_HDMI_PHY_ANA_CFG3_SCLEN |
>  			   SUN8I_HDMI_PHY_ANA_CFG3_SDAEN);
>  
> +	/* reset PLL clock configuration */
> +	regmap_write(phy->regs, SUN8I_HDMI_PHY_PLL_CFG1_REG, 0);
> +	regmap_write(phy->regs, SUN8I_HDMI_PHY_PLL_CFG2_REG, 0);
> +

Ditto,

> +
> +		/*
> +		 * Even though HDMI PHY clock doesn't have enable/disable
> +		 * handlers, we have to enable it. Otherwise it could happen
> +		 * that parent PLL is not enabled by clock framework in a
> +		 * highly unlikely event when parent PLL is used solely for
> +		 * HDMI PHY clock.
> +		 */
> +		clk_prepare_enable(phy->clk_phy);

The implementation of the clock doesn't really matter in our API
usage. If we're using a clock, we have to call
clk_prepare_enable. That's documented everywhere, and mentionning how
the clock is implemented is an abstraction leakage and it's
irrelevant. I'd simply remove the comment here.

And it should be in a separate patch as well.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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