drm/bridge: anx7625: Support reading edid through aux channel

Support reading edid through aux channel if panel is connected to aux
bus. Extend anx7625_aux_dpcd_trans() to implement aux transfer function:

1. panel is populated in devm_of_dp_aux_populate_ep_devices(), so move
   anx7625_parse_dt() after.
2. Use pm runtime autosuspend since aux transfer function is called
   multiple times when reading edid.
3. No-op if aux transfer length is 0.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Xin Ji <xji@analogixsemi.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220213103437.3363848-3-hsinyi@chromium.org

drivers/gpu/drm/bridge/analogix/Kconfig

@@ -32,6 +32,8 @@ config DRM_ANALOGIX_ANX7625
 	tristate "Analogix Anx7625 MIPI to DP interface support"
 	depends on DRM
 	depends on OF
+	select DRM_DP_AUX_BUS
+	select DRM_DP_HELPER
 	select DRM_MIPI_DSI
 	help
 	  ANX7625 is an ultra-low power 4K mobile HD transmitter

drivers/gpu/drm/bridge/analogix/anx7625.c

@@ -24,6 +24,7 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_crtc_helper.h>
+#include <drm/dp/drm_dp_aux_bus.h>
 #include <drm/dp/drm_dp_helper.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_hdcp.h>
@@ -231,19 +232,23 @@ static int wait_aux_op_finish(struct anx7625_data *ctx)
 	return 0;
 }
 
-static int anx7625_aux_dpcd_trans(struct anx7625_data *ctx, u8 op,
-				  u32 address, u8 len, u8 *buf)
+static int anx7625_aux_trans(struct anx7625_data *ctx, u8 op, u32 address,
+			     u8 len, u8 *buf)
 {
 	struct device *dev = &ctx->client->dev;
 	int ret;
 	u8 addrh, addrm, addrl;
 	u8 cmd;
+	bool is_write = !(op & DP_AUX_I2C_READ);
 
-	if (len > MAX_DPCD_BUFFER_SIZE) {
+	if (len > DP_AUX_MAX_PAYLOAD_BYTES) {
 		dev_err(dev, "exceed aux buffer len.\n");
 		return -EINVAL;
 	}
 
+	if (!len)
+		return len;
+
 	addrl = address & 0xFF;
 	addrm = (address >> 8) & 0xFF;
 	addrh = (address >> 16) & 0xFF;
@@ -262,7 +267,7 @@ static int anx7625_aux_dpcd_trans(struct anx7625_data *ctx, u8 op,
 	ret |= anx7625_reg_write(ctx, ctx->i2c.rx_p0_client,
 				 AP_AUX_ADDR_19_16, addrh);
 
-	if (op == DP_AUX_NATIVE_WRITE)
+	if (is_write)
 		ret |= anx7625_reg_block_write(ctx, ctx->i2c.rx_p0_client,
 					       AP_AUX_BUFF_START, len, buf);
 	/* Enable aux access */
@@ -275,14 +280,14 @@ static int anx7625_aux_dpcd_trans(struct anx7625_data *ctx, u8 op,
 	}
 
 	ret = wait_aux_op_finish(ctx);
-	if (ret) {
+	if (ret < 0) {
 		dev_err(dev, "aux IO error: wait aux op finish.\n");
 		return ret;
 	}
 
 	/* Write done */
-	if (op == DP_AUX_NATIVE_WRITE)
-		return 0;
+	if (is_write)
+		return len;
 
 	/* Read done, read out dpcd data */
 	ret = anx7625_reg_block_read(ctx, ctx->i2c.rx_p0_client,
@@ -292,7 +297,7 @@ static int anx7625_aux_dpcd_trans(struct anx7625_data *ctx, u8 op,
 		return -EIO;
 	}
 
-	return 0;
+	return len;
 }
 
 static int anx7625_video_mute_control(struct anx7625_data *ctx,
@@ -867,7 +872,7 @@ static int anx7625_hdcp_enable(struct anx7625_data *ctx)
 	}
 
 	/* Read downstream capability */
-	anx7625_aux_dpcd_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
+	anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
 	if (!(bcap & 0x01)) {
 		pr_warn("downstream not support HDCP 1.4, cap(%x).\n", bcap);
 		return 0;
@@ -956,7 +961,7 @@ static void anx7625_dp_stop(struct anx7625_data *ctx)
 	dev_dbg(dev, "notify downstream enter into standby\n");
 	/* Downstream monitor enter into standby mode */
 	data = 2;
-	ret |= anx7625_aux_dpcd_trans(ctx, DP_AUX_NATIVE_WRITE, 0x000600, 1, &data);
+	ret |= anx7625_aux_trans(ctx, DP_AUX_NATIVE_WRITE, 0x000600, 1, &data);
 	if (ret < 0)
 		DRM_DEV_ERROR(dev, "IO error : mute video fail\n");
 
@@ -1655,11 +1660,56 @@ static int anx7625_parse_dt(struct device *dev,
 	return 0;
 }
 
+static bool anx7625_of_panel_on_aux_bus(struct device *dev)
+{
+	struct device_node *bus, *panel;
+
+	bus = of_get_child_by_name(dev->of_node, "aux-bus");
+	if (!bus)
+		return false;
+
+	panel = of_get_child_by_name(bus, "panel");
+	of_node_put(bus);
+	if (!panel)
+		return false;
+	of_node_put(panel);
+
+	return true;
+}
+
 static inline struct anx7625_data *bridge_to_anx7625(struct drm_bridge *bridge)
 {
 	return container_of(bridge, struct anx7625_data, bridge);
 }
 
+static ssize_t anx7625_aux_transfer(struct drm_dp_aux *aux,
+				    struct drm_dp_aux_msg *msg)
+{
+	struct anx7625_data *ctx = container_of(aux, struct anx7625_data, aux);
+	struct device *dev = &ctx->client->dev;
+	u8 request = msg->request & ~DP_AUX_I2C_MOT;
+	int ret = 0;
+
+	pm_runtime_get_sync(dev);
+	msg->reply = 0;
+	switch (request) {
+	case DP_AUX_NATIVE_WRITE:
+	case DP_AUX_I2C_WRITE:
+	case DP_AUX_NATIVE_READ:
+	case DP_AUX_I2C_READ:
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	if (!ret)
+		ret = anx7625_aux_trans(ctx, msg->request, msg->address,
+					msg->size, msg->buffer);
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	return ret;
+}
+
 static struct edid *anx7625_get_edid(struct anx7625_data *ctx)
 {
 	struct device *dev = &ctx->client->dev;
@@ -2066,6 +2116,13 @@ static int anx7625_bridge_attach(struct drm_bridge *bridge,
 		return -ENODEV;
 	}
 
+	ctx->aux.drm_dev = bridge->dev;
+	err = drm_dp_aux_register(&ctx->aux);
+	if (err) {
+		dev_err(dev, "failed to register aux channel: %d\n", err);
+		return err;
+	}
+
 	if (ctx->pdata.panel_bridge) {
 		err = drm_bridge_attach(bridge->encoder,
 					ctx->pdata.panel_bridge,
@@ -2079,6 +2136,13 @@ static int anx7625_bridge_attach(struct drm_bridge *bridge,
 	return 0;
 }
 
+static void anx7625_bridge_detach(struct drm_bridge *bridge)
+{
+	struct anx7625_data *ctx = bridge_to_anx7625(bridge);
+
+	drm_dp_aux_unregister(&ctx->aux);
+}
+
 static enum drm_mode_status
 anx7625_bridge_mode_valid(struct drm_bridge *bridge,
 			  const struct drm_display_info *info,
@@ -2344,6 +2408,7 @@ static struct edid *anx7625_bridge_get_edid(struct drm_bridge *bridge,
 
 static const struct drm_bridge_funcs anx7625_bridge_funcs = {
 	.attach = anx7625_bridge_attach,
+	.detach = anx7625_bridge_detach,
 	.mode_valid = anx7625_bridge_mode_valid,
 	.mode_set = anx7625_bridge_mode_set,
 	.atomic_check = anx7625_bridge_atomic_check,
@@ -2501,6 +2566,12 @@ static const struct dev_pm_ops anx7625_pm_ops = {
 			   anx7625_runtime_pm_resume, NULL)
 };
 
+static void anx7625_runtime_disable(void *data)
+{
+	pm_runtime_dont_use_autosuspend(data);
+	pm_runtime_disable(data);
+}
+
 static int anx7625_i2c_probe(struct i2c_client *client,
 			     const struct i2c_device_id *id)
 {
@@ -2523,13 +2594,6 @@ static int anx7625_i2c_probe(struct i2c_client *client,
 
 	pdata = &platform->pdata;
 
-	ret = anx7625_parse_dt(dev, pdata);
-	if (ret) {
-		if (ret != -EPROBE_DEFER)
-			DRM_DEV_ERROR(dev, "fail to parse DT : %d\n", ret);
-		return ret;
-	}
-
 	platform->client = client;
 	i2c_set_clientdata(client, platform);
 
@@ -2577,13 +2641,32 @@ static int anx7625_i2c_probe(struct i2c_client *client,
 		}
 	}
 
+	platform->aux.name = "anx7625-aux";
+	platform->aux.dev = dev;
+	platform->aux.transfer = anx7625_aux_transfer;
+	drm_dp_aux_init(&platform->aux);
+	devm_of_dp_aux_populate_ep_devices(&platform->aux);
+
+	ret = anx7625_parse_dt(dev, pdata);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			DRM_DEV_ERROR(dev, "fail to parse DT : %d\n", ret);
+		return ret;
+	}
+
 	if (anx7625_register_i2c_dummy_clients(platform, client) != 0) {
 		ret = -ENOMEM;
 		DRM_DEV_ERROR(dev, "fail to reserve I2C bus.\n");
 		goto free_wq;
 	}
 
 	pm_runtime_enable(dev);
+	pm_runtime_set_autosuspend_delay(dev, 1000);
+	pm_runtime_use_autosuspend(dev);
+	pm_suspend_ignore_children(dev, true);
+	ret = devm_add_action_or_reset(dev, anx7625_runtime_disable, dev);
+	if (ret)
+		return ret;
 
 	if (!platform->pdata.low_power_mode) {
 		anx7625_disable_pd_protocol(platform);
@@ -2596,7 +2679,8 @@ static int anx7625_i2c_probe(struct i2c_client *client,
 
 	platform->bridge.funcs = &anx7625_bridge_funcs;
 	platform->bridge.of_node = client->dev.of_node;
-	platform->bridge.ops = DRM_BRIDGE_OP_EDID;
+	if (!anx7625_of_panel_on_aux_bus(&client->dev))
+		platform->bridge.ops |= DRM_BRIDGE_OP_EDID;
 	if (!platform->pdata.panel_bridge)
 		platform->bridge.ops |= DRM_BRIDGE_OP_HPD |
 					DRM_BRIDGE_OP_DETECT;

drivers/gpu/drm/bridge/analogix/anx7625.h

@@ -472,6 +472,7 @@ struct anx7625_data {
 	u8 bridge_attached;
 	struct drm_connector *connector;
 	struct mipi_dsi_device *dsi;
+	struct drm_dp_aux aux;
 };
 
 #endif  /* __ANX7625_H__ */