linux-kernel - Re: [v4 2/5] drm/mediatek: dpi dual edge support

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Date:   Mon, 20 May 2019 13:56:46 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Jitao Shi <jitao.shi@...iatek.com>
CC:     Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
        "Mark Rutland" <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Kumar Gala <galak@...eaurora.org>, <linux-pwm@...r.kernel.org>,
        David Airlie <airlied@...ux.ie>,
        "Matthias Brugger" <matthias.bgg@...il.com>,
        Thierry Reding <treding@...dia.com>,
        "Ajay Kumar" <ajaykumar.rs@...sung.com>,
        Inki Dae <inki.dae@...sung.com>,
        "Rahul Sharma" <rahul.sharma@...sung.com>,
        Sean Paul <seanpaul@...omium.org>,
        Vincent Palatin <vpalatin@...omium.org>,
        Andy Yan <andy.yan@...k-chips.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "Russell King" <rmk+kernel@....linux.org.uk>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>,
        Sascha Hauer <kernel@...gutronix.de>,
        <yingjoe.chen@...iatek.com>, <eddie.huang@...iatek.com>,
        <cawa.cheng@...iatek.com>, <bibby.hsieh@...iatek.com>,
        <stonea168@....com>
Subject: Re: [v4 2/5] drm/mediatek: dpi dual edge support

Hi, Jitao:

On Sat, 2019-05-18 at 17:56 +0800, Jitao Shi wrote:
> DPI sample the data both rising and falling edge.
> It can reduce half data io pins.

All the registers which you control in this patch exist in MT8173. So I
think this is not a SoC-level feature. This feature depends on how much
io pins you want to use in this platform. Could we get the io pins
information from device tree or calling any driver's api to get? If
there is no way to get this information, I could just temporarily apply
this patch and need plan to fix this temporary solution.

Regards,
CK

> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dpi.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index 22e68a100e7b..ccef3ac1c560 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -117,6 +117,7 @@ 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)
> @@ -353,6 +354,13 @@ static void mtk_dpi_config_disable_edge(struct mtk_dpi *dpi)
>  		mtk_dpi_mask(dpi, dpi->conf->reg_h_fre_con, 0, EDGE_SEL_EN);
>  }
>  
> +static void mtk_dpi_enable_dual_edge(struct mtk_dpi *dpi)
> +{
> +	mtk_dpi_mask(dpi, DPI_DDR_SETTING, DDR_EN | DDR_4PHASE,
> +		     DDR_EN | DDR_4PHASE);
> +	mtk_dpi_mask(dpi, DPI_OUTPUT_SETTING, EDGE_SEL, EDGE_SEL);
> +}
> +
>  static void mtk_dpi_config_color_format(struct mtk_dpi *dpi,
>  					enum mtk_dpi_out_color_format format)
>  {
> @@ -444,7 +452,8 @@ static int mtk_dpi_set_display_mode(struct mtk_dpi *dpi,
>  	pll_rate = clk_get_rate(dpi->tvd_clk);
>  
>  	vm.pixelclock = pll_rate / factor;
> -	clk_set_rate(dpi->pixel_clk, vm.pixelclock);
> +	clk_set_rate(dpi->pixel_clk,
> +		     vm.pixelclock * (dpi->conf->dual_edge ? 2 : 1));
>  	vm.pixelclock = clk_get_rate(dpi->pixel_clk);
>  
>  	dev_dbg(dpi->dev, "Got  PLL %lu Hz, pixel clock %lu Hz\n",
> @@ -509,6 +518,8 @@ static int mtk_dpi_set_display_mode(struct mtk_dpi *dpi,
>  	mtk_dpi_config_color_format(dpi, dpi->color_format);
>  	mtk_dpi_config_2n_h_fre(dpi);
>  	mtk_dpi_config_disable_edge(dpi);
> +	if (dpi->conf->dual_edge)
> +		mtk_dpi_enable_dual_edge(dpi);
>  	mtk_dpi_sw_reset(dpi, false);
>  
>  	return 0;