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Date:   Mon, 21 Oct 2019 13:47:19 -0400
From:   Sean Paul <sean@poorly.run>
To:     Stephan Gerhold <stephan@gerhold.net>
Cc:     Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, Hai Li <hali@codeaurora.org>,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Nikita Travkin <nikitos.tr@gmail.com>
Subject: Re: [PATCH] drm/msm/dsi: Implement qcom,dsi-phy-regulator-ldo-mode
 for 28nm PHY
Message-ID: <20191021174719.GC85762@art_vandelay>
References: <20191021163425.83697-1-stephan@gerhold.net>
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On Mon, Oct 21, 2019 at 06:34:25PM +0200, Stephan Gerhold wrote:
> The DSI PHY regulator supports two regulator modes: LDO and DCDC.
> This mode can be selected using the "qcom,dsi-phy-regulator-ldo-mode"
> device tree property.
> 
> However, at the moment only the 20nm PHY driver actually implements
> that option. Add a check in the 28nm PHY driver to program the
> registers correctly for LDO mode.
> 
> Tested-by: Nikita Travkin <nikitos.tr@gmail.com> # l8150
> Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
> ---
> This is needed to make the display work on Longcheer L8150,
> which has recently gained mainline support in:
> https://git.kernel.org/pub/scm/linux/kernel/git/qcom/linux.git/commit/?id=16e8e8072108426029f0c16dff7fbe77fae3df8f
> 
> This patch is based on code from the downstream kernel:
> https://source.codeaurora.org/quic/la/kernel/msm-3.10/tree/drivers/video/msm/mdss/msm_mdss_io_8974.c?h=LA.BR.1.2.9.1-02310-8x16.0#n152
> 
> The LDO regulator configuration is taken from msm8916-qrd.dtsi:
> https://source.codeaurora.org/quic/la/kernel/msm-3.10/tree/arch/arm/boot/dts/qcom/msm8916-qrd.dtsi?h=LA.BR.1.2.9.1-02310-8x16.0#n56
> ---
>  drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
> index b3f678f6c2aa..4579e6de4532 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
> @@ -48,6 +48,25 @@ static void dsi_28nm_phy_regulator_ctrl(struct msm_dsi_phy *phy, bool enable)
>  		return;
>  	}
>  
> +	if (phy->regulator_ldo_mode) {
> +		u32 ldo_ctrl;
> +
> +		if (phy->cfg->type == MSM_DSI_PHY_28NM_LP)
> +			ldo_ctrl = 0x05;
> +		else
> +			ldo_ctrl = 0x0d;
> +
> +		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_0, 0x0);
> +		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CAL_PWR_CFG, 0);
> +		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_5, 0x7);
> +		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_3, 0);
> +		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_2, 0x1);
> +		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_1, 0x1);
> +		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_4, 0x20);
> +		dsi_phy_write(phy->base + REG_DSI_28nm_PHY_LDO_CNTRL, ldo_ctrl);
> +		return;
> +	}

nit: Since this has minimal overlap with DCDC mode, I think it would read better
if you split this into 2 functions:
dsi_28nm_phy_regulator_enable_dcdc() and dsi_28nm_phy_regulator_enable_ldo()

So regulator_ctrl would look like:

static void dsi_28nm_phy_regulator_ctrl(struct msm_dsi_phy *phy, bool enable)
{
	void __iomem *base = phy->reg_base;

	if (!enable) {
		dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CAL_PWR_CFG, 0);
		return;
	}

	if (phy->regulator_ldo_mode)
                dsi_28nm_phy_regulator_enable_ldo()
        else
                dsi_28nm_phy_regulator_enable_dcdc()
}


> +
>  	dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_0, 0x0);
>  	dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CAL_PWR_CFG, 1);
>  	dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_5, 0);
> @@ -56,6 +75,7 @@ static void dsi_28nm_phy_regulator_ctrl(struct msm_dsi_phy *phy, bool enable)
>  	dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_1, 0x9);
>  	dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_0, 0x7);
>  	dsi_phy_write(base + REG_DSI_28nm_PHY_REGULATOR_CTRL_4, 0x20);
> +	dsi_phy_write(phy->base + REG_DSI_28nm_PHY_LDO_CNTRL, 0x00);
>  }
>  
>  static int dsi_28nm_phy_enable(struct msm_dsi_phy *phy, int src_pll_id,
> @@ -77,8 +97,6 @@ static int dsi_28nm_phy_enable(struct msm_dsi_phy *phy, int src_pll_id,
>  
>  	dsi_28nm_phy_regulator_ctrl(phy, true);
>  
> -	dsi_phy_write(base + REG_DSI_28nm_PHY_LDO_CNTRL, 0x00);
> -
>  	dsi_28nm_dphy_set_timing(phy, timing);
>  
>  	dsi_phy_write(base + REG_DSI_28nm_PHY_CTRL_1, 0x00);
> -- 
> 2.23.0
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS