Re: [PATCH v4 00/13] Apply drm_bridge_connector and panel_bridge helper for the Analogix DP driver

[Damon Ding <damon.ding@rock-chips.com>]

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Hi Marek,

On 9/1/2025 6:25 PM, Marek Szyprowski wrote:
> On 01.09.2025 05:41, Damon Ding wrote:
>> On 8/29/2025 4:23 PM, Marek Szyprowski wrote:
>>> On 29.08.2025 10:08, Damon Ding wrote:
>>>> On 8/20/2025 5:20 AM, Marek Szyprowski wrote:
>>>>> On 15.08.2025 04:59, Damon Ding wrote:
>>>>>> On 2025/8/15 5:16, Marek Szyprowski wrote:
>>>>>>> On 14.08.2025 16:33, Marek Szyprowski wrote:
>>>>>>>> On 14.08.2025 12:47, Damon Ding wrote:
>>>>>>>>> PATCH 1 is a small format optimization for struct
>>>>>>>>> analogid_dp_device.
>>>>>>>>> PATCH 2 is to perform mode setting in
>>>>>>>>> &drm_bridge_funcs.atomic_enable.
>>>>>>>>> PATCH 3-6 are preparations for apply drm_bridge_connector helper.
>>>>>>>>> PATCH 7 is to apply the drm_bridge_connector helper.
>>>>>>>>> PATCH 8-10 are to move the panel/bridge parsing to the Analogix
>>>>>>>>> side.
>>>>>>>>> PATCH 11-12 are preparations for apply panel_bridge helper.
>>>>>>>>> PATCH 13 is to apply the panel_bridge helper.
>>>>>>>>
>>>>>>>> This series lacks 'select DRM_BRIDGE_CONNECTOR' in ExynosDP's
>>>>>>>> Kconfig,
>>>>>>>> so it causes build break:
>>>>>>>>
>>>>>>>> drivers/gpu/drm/exynos/exynos_dp.c:177: undefined reference to
>>>>>>>> `drm_bridge_connector_init'
>>>>>>>> make[2]: *** [scripts/Makefile.vmlinux:91: vmlinux] Error 1
>>>>>>>>
>>>>>>>> After adding this dependency, the Exynos DP driver stops
>>>>>>>> working. On
>>>>>>>> Samsung Snow Chromebook I observed following issue:
>>>>>>>>
>>>>>>>> [    4.534220] exynos-dp 145b0000.dp-controller: failed to attach
>>>>>>>> following panel or bridge (-16)
>>>>>>>> [    4.543428] exynos-drm exynos-drm: failed to bind
>>>>>>>> 145b0000.dp-controller (ops exynos_dp_ops): -16
>>>>>>>> [    4.551775] exynos-drm exynos-drm: adev bind failed: -16
>>>>>>>> [    4.556559] exynos-dp 145b0000.dp-controller: probe with driver
>>>>>>>> exynos-dp failed with error -16
>>>>>>>>
>>>>>>>> I will investigate details later in the evening.
>>>>>>>
>>>>>>> The failure is caused by trying to add plat_data->next_bridge twice
>>>>>>> (from exynos_dp's .attach callback, and from analogix' ->bind
>>>>>>> callback).
>>>>>>>
>>>>>>>
>>>>>>> Best regards
>>>>>>
>>>>>> I see. The bridge attachment for the next bridge was not well thought
>>>>>> out. It may be better to move panel_bridge addition a little forward
>>>>>> and remove next_bridge attachment on the Analogix side. Then, the
>>>>>> Rockchip side and Exynos side can do their own next_bridge attachment
>>>>>> in &analogix_dp_plat_data.attach() as they want.
>>>>>>
>>>>>> Could you please help test the following modifications(they have been
>>>>>> tested on my RK3588S EVB1 Board) on the Samsung Snow Chromebook? ;-)
>>>>>
>>>>> Assuming that I properly applied the malformed diff, it doesn't solve
>>>>> all the issues. There are no errors reported though, but the display
>>>>> chain doesn't work and no valid mode is reported:
>>>>>
>>>>> # dmesg | grep drm
>>>>> [    3.384992] [drm] Initialized panfrost 1.4.0 for 11800000.gpu on
>>>>> minor 0
>>>>> [    4.487739] [drm] Exynos DRM: using 14400000.fimd device for DMA
>>>>> mapping operations
>>>>> [    4.494202] exynos-drm exynos-drm: bound 14400000.fimd (ops
>>>>> fimd_component_ops)
>>>>> [    4.502374] exynos-drm exynos-drm: bound 14450000.mixer (ops
>>>>> mixer_component_ops)
>>>>> [    4.511930] exynos-drm exynos-drm: bound 145b0000.dp-controller
>>>>> (ops
>>>>> exynos_dp_ops)
>>>>> [    4.518411] exynos-drm exynos-drm: bound 14530000.hdmi (ops
>>>>> hdmi_component_ops)
>>>>> [    4.529628] [drm] Initialized exynos 1.1.0 for exynos-drm on
>>>>> minor 1
>>>>> [    4.657434] exynos-drm exynos-drm: [drm] Cannot find any crtc or
>>>>> sizes
>>>>> [    4.925023] exynos-drm exynos-drm: [drm] Cannot find any crtc or
>>>>> sizes
>>>>>
>>>>> # ./modetest -c -Mexynos
>>>>> Connectors:
>>>>> id      encoder status          name            size (mm)       modes
>>>>>       encoders
>>>>> 69      0       disconnected    LVDS-1          0x0             0
>>>>>         68
>>>>>      props:
>>>>>            1 EDID:
>>>>>                    flags: immutable blob
>>>>>                    blobs:
>>>>>
>>>>>                    value:
>>>>>            2 DPMS:
>>>>>                    flags: enum
>>>>>                    enums: On=0 Standby=1 Suspend=2 Off=3
>>>>>                    value: 0
>>>>>            5 link-status:
>>>>>                    flags: enum
>>>>>                    enums: Good=0 Bad=1
>>>>>                    value: 0
>>>>>            6 non-desktop:
>>>>>                    flags: immutable range
>>>>>                    values: 0 1
>>>>>                    value: 0
>>>>>            4 TILE:
>>>>>                    flags: immutable blob
>>>>>                    blobs:
>>>>>
>>>>>                    value:
>>>>> 71      0       disconnected    HDMI-A-1        0x0             0
>>>>>         70
>>>>>      props:
>>>>>            1 EDID:
>>>>>                    flags: immutable blob
>>>>>                    blobs:
>>>>>
>>>>>                    value:
>>>>>            2 DPMS:
>>>>>                    flags: enum
>>>>>                    enums: On=0 Standby=1 Suspend=2 Off=3
>>>>>                    value: 0
>>>>>            5 link-status:
>>>>>                    flags: enum
>>>>>                    enums: Good=0 Bad=1
>>>>>                    value: 0
>>>>>            6 non-desktop:
>>>>>                    flags: immutable range
>>>>>                    values: 0 1
>>>>>                    value: 0
>>>>>            4 TILE:
>>>>>                    flags: immutable blob
>>>>>                    blobs:
>>>>>
>>>>>                    value:
>>>>>
>>>>>
>>>>> I will investigate details later this week.
>>>>>
>>>>
>>>> Could you please provide the related DTS file for the test? I will
>>>> also try to find out the reason for this unexpected issue. ;-)
>>>
>>> Unfortunately I didn't find enough time to debug this further. The above
>>> log is from Samsung Snow Chromebook,
>>> arch/arm/boot/dts/samsung/exynos5250-snow.dts
>>>
>>>
>>
>> I compare the differences in the following display path before and
>> after this patch series:
>>
>> exynos_dp -> nxp-ptn3460 -> panel "auo,b116xw03"
>>
>> The issue is likely caused by the &drm_connector_funcs.detect()
>> related logic. Before this patch series, the nxp-ptn3460 connector is
>> always connector_status_connected because there is not available
>> &drm_connector_funcs.detect(). After it, the DRM_BRIDGE_OP_DETECT flag
>> make the connection status depend on analogix_dp_bridge_detect().
>>
>> Could you please add the following patches additionally and try again?
>> (Not the final solution, just validation)
>>
>> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> index a93ff8f0a468..355911c47354 100644
>> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> @@ -1491,9 +1491,11 @@ int analogix_dp_bind(struct analogix_dp_device
>> *dp, struct drm_device *drm_dev)
>>                  }
>>          }
>>
>> -       bridge->ops = DRM_BRIDGE_OP_DETECT |
>> -                     DRM_BRIDGE_OP_EDID |
>> +       bridge->ops = DRM_BRIDGE_OP_EDID |
>>                        DRM_BRIDGE_OP_MODES;
>> +       if (drm_bridge_is_panel(dp->plat_data->next_bridge))
>> +               bridge->ops |= DRM_BRIDGE_OP_DETECT;
>> +
>>          bridge->of_node = dp->dev->of_node;
>>          bridge->type = DRM_MODE_CONNECTOR_eDP;
>>          ret = devm_drm_bridge_add(dp->dev, &dp->bridge);
> 
> It is better. Now the display panel is detected and reported to
> userspace, but it looks that something is not properly initialized,
> because there is garbage instead of the proper picture.
> 

I simulated the display path mentioned above on my RK3588S EVB1 Board.
To my slight surprise, it displayed normally with the reported connector 
type DRM_MODE_CONNECTOR_LVDS. ;-)

The modifications included:
1.Synchronized the Analogix DP ralated DT configurations with Samsung 
Snow Chromebook.
2.Skipped the I2C transfers and GPIO operations in nxp-ptn3460 driver.
3.Set the EDID to that of eDP Panel LP079QX1-SP0V forcibly.

Additionally, I added debug logs to verify whether the functions in 
ptn3460_bridge_funcs were actually called.

Did you encounter any unexpected logs during your investigation? I'd 
like to perform additional tests on this issue. :-)

Best regards,
Damon

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diff --git a/arch/arm64/boot/dts/rockchip/rk3588s-evb1-v10.dts b/arch/arm64/boot/dts/rockchip/rk3588s-evb1-v10.dts
index 0df3e80f2dd9..51ce63fce6ee 100644
--- a/arch/arm64/boot/dts/rockchip/rk3588s-evb1-v10.dts
+++ b/arch/arm64/boot/dts/rockchip/rk3588s-evb1-v10.dts
@@ -26,6 +26,18 @@ chosen {
 		stdout-path = "serial2:1500000n8";
 	};
 
+	panel: panel {
+		compatible = "auo,b116xw03";
+		power-supply = <&vcc3v3_lcd_edp>;
+		backlight = <&backlight>;
+
+		port {
+			panel_in: endpoint {
+				remote-endpoint = <&bridge_out>;
+			};
+		};
+	};
+
 	adc-keys {
 		compatible = "adc-keys";
 		io-channels = <&saradc 1>;
@@ -242,21 +254,6 @@ &combphy2_psu {
 &edp0 {
 	force-hpd;
 	status = "okay";
-
-	aux-bus {
-		panel {
-			compatible = "edp-panel";
-			backlight = <&backlight>;
-			power-supply = <&vcc3v3_lcd_edp>;
-			no-hpd;
-
-			port {
-				panel_in_edp: endpoint {
-					remote-endpoint = <&edp_out_panel>;
-				};
-			};
-		};
-	};
 };
 
 &edp0_in {
@@ -266,8 +263,8 @@ edp0_in_vp2: endpoint {
 };
 
 &edp0_out {
-	edp_out_panel: endpoint {
-		remote-endpoint = <&panel_in_edp>;
+	dp_out: endpoint {
+		remote-endpoint = <&bridge_in>;
 	};
 };
 
@@ -290,6 +287,33 @@ es8388: audio-codec@11 {
 		PVDD-supply = <&vcc_3v3_s0>;
 		#sound-dai-cells = <0>;
 	};
+
+	ptn3460: lvds-bridge@20 {
+		compatible = "nxp,ptn3460";
+		reg = <0x20>;
+		edid-emulation = <5>;
+
+		ports {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			port@0 {
+				reg = <0>;
+
+				bridge_out: endpoint {
+					remote-endpoint = <&panel_in>;
+				};
+			};
+
+			port@1 {
+				reg = <1>;
+
+				bridge_in: endpoint {
+					remote-endpoint = <&dp_out>;
+				};
+			};
+		};
+	};
 };
 
 &i2c8 {
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index a93ff8f0a468..355911c47354 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1491,9 +1491,11 @@ int analogix_dp_bind(struct analogix_dp_device *dp, struct drm_device *drm_dev)
 		}
 	}
 
-	bridge->ops = DRM_BRIDGE_OP_DETECT |
-		      DRM_BRIDGE_OP_EDID |
+	bridge->ops = DRM_BRIDGE_OP_EDID |
 		      DRM_BRIDGE_OP_MODES;
+	if (drm_bridge_is_panel(dp->plat_data->next_bridge))
+		bridge->ops |= DRM_BRIDGE_OP_DETECT;
+
 	bridge->of_node = dp->dev->of_node;
 	bridge->type = DRM_MODE_CONNECTOR_eDP;
 	ret = devm_drm_bridge_add(dp->dev, &dp->bridge);
diff --git a/drivers/gpu/drm/bridge/nxp-ptn3460.c b/drivers/gpu/drm/bridge/nxp-ptn3460.c
index 7acb11f16dc1..cafbdcda2d29 100644
--- a/drivers/gpu/drm/bridge/nxp-ptn3460.c
+++ b/drivers/gpu/drm/bridge/nxp-ptn3460.c
@@ -52,6 +52,7 @@ static int ptn3460_read_bytes(struct ptn3460_bridge *ptn_bridge, char addr,
 {
 	int ret;
 
+	return 0;
 	ret = i2c_master_send(ptn_bridge->client, &addr, 1);
 	if (ret < 0) {
 		DRM_ERROR("Failed to send i2c command, ret=%d\n", ret);
@@ -90,6 +91,7 @@ static int ptn3460_select_edid(struct ptn3460_bridge *ptn_bridge)
 	int ret;
 	char val;
 
+	return 0;
 	/* Load the selected edid into SRAM (accessed at PTN3460_EDID_ADDR) */
 	ret = ptn3460_write_byte(ptn_bridge, PTN3460_EDID_SRAM_LOAD_ADDR,
 			ptn_bridge->edid_emulation);
@@ -152,6 +154,21 @@ static void ptn3460_disable(struct drm_bridge *bridge)
 	gpiod_set_value(ptn_bridge->gpio_pd_n, 0);
 }
 
+static const u8 edid_data[] = {
+    0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x16, 0x83,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x17, 0x01, 0x00,
+    0xA5, 0x10, 0x0C, 0x78, 0x06, 0xEF, 0x05, 0xA3, 0x54, 0x4C,
+    0x99, 0x26, 0x0F, 0x50, 0x54, 0x00, 0x00, 0x00, 0x01, 0x01,
+    0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+    0x01, 0x01, 0x01, 0x01, 0xEA, 0x4E, 0x00, 0x4C, 0x60, 0x00,
+    0x14, 0x80, 0x0C, 0x10, 0x84, 0x00, 0x78, 0xA0, 0x00, 0x00,
+    0x00, 0x18, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0xFE, 0x00, 0x4C, 0x50, 0x30, 0x37, 0x39,
+    0x51, 0x58, 0x31, 0x2D, 0x53, 0x50, 0x30, 0x56, 0x00, 0x00,
+    0x00, 0xFC, 0x00, 0x43, 0x6F, 0x6C, 0x6F, 0x72, 0x20, 0x4C,
+    0x43, 0x44, 0x0A, 0x20, 0x20, 0x20, 0x00, 0x3F
+};
 
 static const struct drm_edid *ptn3460_edid_read(struct drm_bridge *bridge,
 						struct drm_connector *connector)
@@ -178,7 +195,8 @@ static const struct drm_edid *ptn3460_edid_read(struct drm_bridge *bridge,
 		goto out;
 	}
 
-	drm_edid = drm_edid_alloc(edid, EDID_LENGTH);
+	kfree(edid);
+	drm_edid = drm_edid_alloc(edid_data, EDID_LENGTH);
 
 out:
 	if (power_off)
@@ -273,7 +291,7 @@ static int ptn3460_probe(struct i2c_client *client)
 	ptn_bridge->panel_bridge = panel_bridge;
 	ptn_bridge->client = client;
 
-	ptn_bridge->gpio_pd_n = devm_gpiod_get(&client->dev, "powerdown",
+	ptn_bridge->gpio_pd_n = devm_gpiod_get_optional(&client->dev, "powerdown",
 					       GPIOD_OUT_HIGH);
 	if (IS_ERR(ptn_bridge->gpio_pd_n)) {
 		ret = PTR_ERR(ptn_bridge->gpio_pd_n);
@@ -285,7 +303,7 @@ static int ptn3460_probe(struct i2c_client *client)
 	 * Request the reset pin low to avoid the bridge being
 	 * initialized prematurely
 	 */
-	ptn_bridge->gpio_rst_n = devm_gpiod_get(&client->dev, "reset",
+	ptn_bridge->gpio_rst_n = devm_gpiod_get_optional(&client->dev, "reset",
 						GPIOD_OUT_LOW);
 	if (IS_ERR(ptn_bridge->gpio_rst_n)) {
 		ret = PTR_ERR(ptn_bridge->gpio_rst_n);
diff --git a/drivers/gpu/drm/exynos/exynos_dp.c b/drivers/gpu/drm/exynos/exynos_dp.c
index 80ba700d2964..d0422f940249 100644
--- a/drivers/gpu/drm/exynos/exynos_dp.c
+++ b/drivers/gpu/drm/exynos/exynos_dp.c
@@ -104,7 +104,7 @@ static int exynos_dp_bridge_attach(struct analogix_dp_plat_data *plat_data,
 	/* Pre-empt DP connector creation if there's a bridge */
 	if (plat_data->next_bridge) {
 		ret = drm_bridge_attach(&dp->encoder, plat_data->next_bridge, bridge,
-					0);
+					DRM_BRIDGE_ATTACH_NO_CONNECTOR);
 		if (ret)
 			return ret;
 	}