[PATCH] drm/msm/dsi: Implement qcom,dsi-phy-regulator-ldo-mode for 28nm PHY

[Stephan Gerhold <stephan@gerhold.net>]

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;
+	}
+
 	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