drm/bridge: analogix_dp: Set PD_INC_BG first when powering up edp phy

Following the correct power up sequence:
dp_pd=ff => dp_pd=7f => wait 10us => dp_pd=00

Cc: Stéphane Marchesin <marcheu@chromium.org>
Signed-off-by: zain wang <wzz@rock-chips.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180423105003.9004-7-enric.balletbo@collabora.com

drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c

@@ -321,10 +321,16 @@ void analogix_dp_set_analog_power_down(struct analogix_dp_device *dp,
 		break;
 	case POWER_ALL:
 		if (enable) {
-			reg = DP_PHY_PD | AUX_PD | CH3_PD | CH2_PD |
-				CH1_PD | CH0_PD;
+			reg = DP_ALL_PD;
 			writel(reg, dp->reg_base + phy_pd_addr);
 		} else {
+			reg = DP_ALL_PD;
+			writel(reg, dp->reg_base + phy_pd_addr);
+			usleep_range(10, 15);
+			reg &= ~DP_INC_BG;
+			writel(reg, dp->reg_base + phy_pd_addr);
+			usleep_range(10, 15);
+
 			writel(0x00, dp->reg_base + phy_pd_addr);
 		}
 		break;

drivers/gpu/drm/bridge/analogix/analogix_dp_reg.h

@@ -342,12 +342,15 @@
 #define DP_PLL_REF_BIT_1_2500V			(0x7 << 0)
 
 /* ANALOGIX_DP_PHY_PD */
+#define DP_INC_BG				(0x1 << 7)
+#define DP_EXP_BG				(0x1 << 6)
 #define DP_PHY_PD				(0x1 << 5)
 #define AUX_PD					(0x1 << 4)
 #define CH3_PD					(0x1 << 3)
 #define CH2_PD					(0x1 << 2)
 #define CH1_PD					(0x1 << 1)
 #define CH0_PD					(0x1 << 0)
+#define DP_ALL_PD				(0xff)
 
 /* ANALOGIX_DP_PHY_TEST */
 #define MACRO_RST				(0x1 << 5)