drm/bridge: ti-sn65dsi86: Group DP link training bits in a function

We'll re-organize the ti_sn_bridge_enable() function a bit to group
together all the parts relating to link training and split them into a
sub-function.  This is not intended to have any functional change and
is in preparation for trying link training several times at different
rates.  One small side effect here is that if link training fails
we'll now leave the DP PLL disabled, but that seems like a sane thing
to do.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191218143416.v3.7.I1fc75ad11db9048ef08cfe1ab7322753d9a219c7@changeid

drivers/gpu/drm/bridge/ti-sn65dsi86.c

@@ -530,6 +530,46 @@ static unsigned int ti_sn_get_max_lanes(struct ti_sn_bridge *pdata)
 	return data & DP_LANE_COUNT_MASK;
 }
 
+static int ti_sn_link_training(struct ti_sn_bridge *pdata)
+{
+	unsigned int val;
+	int ret;
+
+	/* set dp clk frequency value */
+	ti_sn_bridge_set_dp_rate(pdata);
+
+	/* enable DP PLL */
+	regmap_write(pdata->regmap, SN_PLL_ENABLE_REG, 1);
+
+	ret = regmap_read_poll_timeout(pdata->regmap, SN_DPPLL_SRC_REG, val,
+				       val & DPPLL_SRC_DP_PLL_LOCK, 1000,
+				       50 * 1000);
+	if (ret) {
+		DRM_ERROR("DP_PLL_LOCK polling failed (%d)\n", ret);
+		goto exit;
+	}
+
+	/* Semi auto link training mode */
+	regmap_write(pdata->regmap, SN_ML_TX_MODE_REG, 0x0A);
+	ret = regmap_read_poll_timeout(pdata->regmap, SN_ML_TX_MODE_REG, val,
+				       val == ML_TX_MAIN_LINK_OFF ||
+				       val == ML_TX_NORMAL_MODE, 1000,
+				       500 * 1000);
+	if (ret) {
+		DRM_ERROR("Training complete polling failed (%d)\n", ret);
+	} else if (val == ML_TX_MAIN_LINK_OFF) {
+		DRM_ERROR("Link training failed, link is off\n");
+		ret = -EIO;
+	}
+
+exit:
+	/* Disable the PLL if we failed */
+	if (ret)
+		regmap_write(pdata->regmap, SN_PLL_ENABLE_REG, 0);
+
+	return ret;
+}
+
 static void ti_sn_bridge_enable(struct drm_bridge *bridge)
 {
 	struct ti_sn_bridge *pdata = bridge_to_ti_sn_bridge(bridge);
@@ -555,29 +595,8 @@ static void ti_sn_bridge_enable(struct drm_bridge *bridge)
 	regmap_update_bits(pdata->regmap, SN_DSI_LANES_REG,
 			   CHA_DSI_LANES_MASK, val);
 
-	/* Set the DP output format (18 bpp or 24 bpp) */
-	val = (ti_sn_bridge_get_bpp(pdata) == 18) ? BPP_18_RGB : 0;
-	regmap_update_bits(pdata->regmap, SN_DATA_FORMAT_REG, BPP_18_RGB, val);
-
-	/* DP lane config */
-	val = DP_NUM_LANES(min(pdata->dp_lanes, 3));
-	regmap_update_bits(pdata->regmap, SN_SSC_CONFIG_REG, DP_NUM_LANES_MASK,
-			   val);
-
-	/* set dsi/dp clk frequency value */
+	/* set dsi clk frequency value */
 	ti_sn_bridge_set_dsi_rate(pdata);
-	ti_sn_bridge_set_dp_rate(pdata);
-
-	/* enable DP PLL */
-	regmap_write(pdata->regmap, SN_PLL_ENABLE_REG, 1);
-
-	ret = regmap_read_poll_timeout(pdata->regmap, SN_DPPLL_SRC_REG, val,
-				       val & DPPLL_SRC_DP_PLL_LOCK, 1000,
-				       50 * 1000);
-	if (ret) {
-		DRM_ERROR("DP_PLL_LOCK polling failed (%d)\n", ret);
-		return;
-	}
 
 	/**
 	 * The SN65DSI86 only supports ASSR Display Authentication method and
@@ -588,19 +607,18 @@ static void ti_sn_bridge_enable(struct drm_bridge *bridge)
 	drm_dp_dpcd_writeb(&pdata->aux, DP_EDP_CONFIGURATION_SET,
 			   DP_ALTERNATE_SCRAMBLER_RESET_ENABLE);
 
-	/* Semi auto link training mode */
-	regmap_write(pdata->regmap, SN_ML_TX_MODE_REG, 0x0A);
-	ret = regmap_read_poll_timeout(pdata->regmap, SN_ML_TX_MODE_REG, val,
-				       val == ML_TX_MAIN_LINK_OFF ||
-				       val == ML_TX_NORMAL_MODE, 1000,
-				       500 * 1000);
-	if (ret) {
-		DRM_ERROR("Training complete polling failed (%d)\n", ret);
-		return;
-	} else if (val == ML_TX_MAIN_LINK_OFF) {
-		DRM_ERROR("Link training failed, link is off\n");
+	/* Set the DP output format (18 bpp or 24 bpp) */
+	val = (ti_sn_bridge_get_bpp(pdata) == 18) ? BPP_18_RGB : 0;
+	regmap_update_bits(pdata->regmap, SN_DATA_FORMAT_REG, BPP_18_RGB, val);
+
+	/* DP lane config */
+	val = DP_NUM_LANES(min(pdata->dp_lanes, 3));
+	regmap_update_bits(pdata->regmap, SN_SSC_CONFIG_REG, DP_NUM_LANES_MASK,
+			   val);
+
+	ret = ti_sn_link_training(pdata);
+	if (ret)
 		return;
-	}
 
 	/* config video parameters */
 	ti_sn_bridge_set_video_timings(pdata);