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Date:   Fri, 9 Apr 2021 13:35:32 +0800
From:   Xin Ji <xji@analogixsemi.com>
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        Nicolas Boichat <drinkcat@google.com>,
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Subject: [PATCH 1/1] drm/bridge: anx7625: send DPCD command to downstream
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Send DPCD command to downstream before anx7625 power down,
tell downstream into standby mode.

Signed-off-by: Xin Ji <xji@analogixsemi.com>
---
 drivers/gpu/drm/bridge/analogix/anx7625.c | 75 +++++++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
index 65cc05982f82..53d2f0d0ee30 100644
--- a/drivers/gpu/drm/bridge/analogix/anx7625.c
+++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
@@ -124,6 +124,23 @@ static int anx7625_reg_write(struct anx7625_data *ctx,
 	return ret;
 }
 
+static int anx7625_reg_block_write(struct anx7625_data *ctx,
+				   struct i2c_client *client,
+				   u8 reg_addr, u8 len, u8 *buf)
+{
+	int ret;
+	struct device *dev = &client->dev;
+
+	i2c_access_workaround(ctx, client);
+
+	ret = i2c_smbus_write_i2c_block_data(client, reg_addr, len, buf);
+	if (ret < 0)
+		DRM_DEV_ERROR(dev, "write i2c block failed id=%x\n:%x",
+			      client->addr, reg_addr);
+
+	return ret;
+}
+
 static int anx7625_write_or(struct anx7625_data *ctx,
 			    struct i2c_client *client,
 			    u8 offset, u8 mask)
@@ -195,6 +212,55 @@ static int wait_aux_op_finish(struct anx7625_data *ctx)
 	return val;
 }
 
+static int anx7625_aux_dpcd_write(struct anx7625_data *ctx,
+				  u8 addrh, u8 addrm, u8 addrl,
+				  u8 len, u8 *buf)
+{
+	struct device *dev = &ctx->client->dev;
+	int ret;
+	u8 cmd;
+
+	if (len > MAX_DPCD_BUFFER_SIZE) {
+		DRM_DEV_ERROR(dev, "exceed aux buffer len.\n");
+		return -EINVAL;
+	}
+
+	cmd = ((len - 1) << 4) | 0x08;
+
+	/* Set command and length */
+	ret = anx7625_reg_write(ctx, ctx->i2c.rx_p0_client,
+				AP_AUX_COMMAND, cmd);
+
+	/* Set aux access address */
+	ret |= anx7625_reg_write(ctx, ctx->i2c.rx_p0_client,
+				 AP_AUX_ADDR_7_0, addrl);
+	ret |= anx7625_reg_write(ctx, ctx->i2c.rx_p0_client,
+				 AP_AUX_ADDR_15_8, addrm);
+	ret |= anx7625_write_and(ctx, ctx->i2c.rx_p0_client,
+				 AP_AUX_ADDR_19_16, addrh);
+
+	/* Set write data */
+	ret |= anx7625_reg_block_write(ctx, ctx->i2c.rx_p0_client,
+				       AP_AUX_BUFF_START, len, buf);
+	/* Enable aux access */
+	ret |= anx7625_write_or(ctx, ctx->i2c.rx_p0_client,
+				AP_AUX_CTRL_STATUS, AP_AUX_CTRL_OP_EN);
+	if (ret < 0) {
+		DRM_DEV_ERROR(dev, "cannot access aux related register.\n");
+		return -EIO;
+	}
+
+	usleep_range(2000, 2100);
+
+	ret = wait_aux_op_finish(ctx);
+	if (ret) {
+		DRM_DEV_ERROR(dev, "aux IO error: wait aux op finish.\n");
+		return ret;
+	}
+
+	return 0;
+}
+
 static int anx7625_video_mute_control(struct anx7625_data *ctx,
 				      u8 status)
 {
@@ -617,6 +683,7 @@ static void anx7625_dp_stop(struct anx7625_data *ctx)
 {
 	struct device *dev = &ctx->client->dev;
 	int ret;
+	u8 data;
 
 	DRM_DEV_DEBUG_DRIVER(dev, "stop dp output\n");
 
@@ -628,8 +695,16 @@ static void anx7625_dp_stop(struct anx7625_data *ctx)
 	ret |= anx7625_write_and(ctx, ctx->i2c.tx_p2_client, 0x08, 0x7f);
 
 	ret |= anx7625_video_mute_control(ctx, 1);
+
+	DRM_DEV_DEBUG_DRIVER(dev, "notify downstream enter into standby\n");
+
+	/* Downstream monitor enter into standby mode */
+	data = 2;
+	ret |= anx7625_aux_dpcd_write(ctx, 0x00, 0x06, 0x00, 1, &data);
 	if (ret < 0)
 		DRM_DEV_ERROR(dev, "IO error : mute video fail\n");
+
+	return;
 }
 
 static int sp_tx_rst_aux(struct anx7625_data *ctx)
-- 
2.25.1