linux-kernel - Re: [PATCH] drm/meson: fix G12A HDMI PLL settings for 4K60 1000/1001 variations

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Date:   Thu, 06 Jun 2019 09:30:52 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Neil Armstrong <narmstrong@...libre.com>,
        dri-devel@...ts.freedesktop.org
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/meson: fix G12A HDMI PLL settings for 4K60 1000/1001 variations

Neil Armstrong <narmstrong@...libre.com> writes:

> The Amlogic G12A HDMI PLL needs some specific settings to lock with
> different fractional values for the 5,4GHz mode.
>
> Handle the 1000/1001 variation fractional case here to avoid having
> the PLL in an non lockable state.
>
> Fixes: 202b9808f8ed ("drm/meson: Add G12A Video Clock setup")
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  drivers/gpu/drm/meson/meson_vclk.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/meson/meson_vclk.c b/drivers/gpu/drm/meson/meson_vclk.c
> index 44250eff8a3f..83fc2fc82001 100644
> --- a/drivers/gpu/drm/meson/meson_vclk.c
> +++ b/drivers/gpu/drm/meson/meson_vclk.c
> @@ -553,8 +553,17 @@ void meson_hdmi_pll_set_params(struct meson_drm *priv, unsigned int m,
>  
>  		/* G12A HDMI PLL Needs specific parameters for 5.4GHz */
>  		if (m >= 0xf7) {
> -			regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL4, 0xea68dc00);
> -			regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL5, 0x65771290);
> +			if (frac < 0x10000) {
> +				regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL4,
> +							0x6a685c00);
> +				regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL5,
> +							0x11551293);
> +			} else {
> +				regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL4,
> +							0xea68dc00);
> +				regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL5,
> +							0x65771290);
> +			}
>  			regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL6, 0x39272000);
>  			regmap_write(priv->hhi, HHI_HDMI_PLL_CNTL7, 0x55540000);
>  		} else {

Reviewed-by: Kevin Hilman <khilman@...libre.com>

nit: this is continuing with more magic constants, and it would be nice
to have them converted to #define'd bitfields.  But since that isn't a
new problem in this patch, it's fine to cleanup later.

Kevin