linux-kernel - Re: [v2,PATCH 1/3] drm/mediatek: dpi dual edge sample mode support

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Date:   Mon, 19 Apr 2021 09:36:42 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Rex-BC Chen <rex-bc.chen@...iatek.com>, chunkuang.hu@...nel.org,
        matthias.bgg@...il.com
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        Jitao Shi <jitao.shi@...iatek.com>
Subject: Re: [v2,PATCH 1/3] drm/mediatek: dpi dual edge sample mode support

Hi,

On 14/04/2021 15:35, Rex-BC Chen wrote:
> DPI can sample on falling, rising or both edge.
> When DPI sample the data both rising and falling edge.
> It can reduce half data io pins.
> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> Signed-off-by: Rex-BC Chen <rex-bc.chen@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dpi.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index b05f900d9322..21a3a7b78835 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -83,6 +83,7 @@ struct mtk_dpi {
>  	struct pinctrl *pinctrl;
>  	struct pinctrl_state *pins_gpio;
>  	struct pinctrl_state *pins_dpi;
> +	bool ddr_edge_sel;
>  	int refcount;
>  };
>  
> @@ -121,6 +122,7 @@ struct mtk_dpi_conf {
>  	unsigned int (*cal_factor)(int clock);
>  	u32 reg_h_fre_con;
>  	bool edge_sel_en;
> +	bool dual_edge;
>  };
>  
>  static void mtk_dpi_mask(struct mtk_dpi *dpi, u32 offset, u32 val, u32 mask)
> @@ -380,6 +382,15 @@ static void mtk_dpi_config_color_format(struct mtk_dpi *dpi,
>  	}
>  }
>  
> +static void mtk_dpi_dual_edge(struct mtk_dpi *dpi)
> +{
> +	if (dpi->conf->dual_edge) {
> +		mtk_dpi_mask(dpi, DPI_DDR_SETTING, DDR_EN | DDR_4PHASE,
> +			     DDR_EN | DDR_4PHASE);
> +		mtk_dpi_mask(dpi, DPI_OUTPUT_SETTING, dpi->ddr_edge_sel ? EDGE_SEL : 0, EDGE_SEL);
> +	}
> +}
> +

By using the downstream code as reference:

-       clk_set_rate(dpi->pixel_clk, vm.pixelclock);
+       clk_set_rate(dpi->pixel_clk, vm.pixelclock * (dpi->conf->dual_edge ? 2 : 1));

is missing in mtk_dpi_set_display_mode()

>  static void mtk_dpi_power_off(struct mtk_dpi *dpi)
>  {
>  	if (WARN_ON(dpi->refcount == 0))
> @@ -518,6 +529,7 @@ static int mtk_dpi_set_display_mode(struct mtk_dpi *dpi,
>  	mtk_dpi_config_yc_map(dpi, dpi->yc_map);
>  	mtk_dpi_config_color_format(dpi, dpi->color_format);
>  	mtk_dpi_config_2n_h_fre(dpi);
> +	mtk_dpi_dual_edge(dpi);
>  	mtk_dpi_config_disable_edge(dpi);
>  	mtk_dpi_sw_reset(dpi, false);
>  
> 

Neil