[v1] drm/panel: simple: restore connector_type fallback

[PATCH REGRESSION] drm/panel: simple: restore connector_type fallback

Posted by Ludovic Desroches 1 week, 3 days ago

The switch from devm_kzalloc() + drm_panel_init() to
devm_drm_panel_alloc() introduced a regression.

Several panel descriptors do not set connector_type. For those panels,
panel_simple_probe() used to compute a connector type (currently DPI as a
fallback) and pass that value to drm_panel_init(). After the conversion
to devm_drm_panel_alloc(), the call unconditionally used
desc->connector_type instead, ignoring the computed fallback and
potentially passing DRM_MODE_CONNECTOR_Unknown, which
drm_panel_bridge_add() does not allow.

Move the connector_type validation / fallback logic before the
devm_drm_panel_alloc() call and pass the computed connector_type to
devm_drm_panel_alloc(), so panels without an explicit connector_type
once again get the DPI default.

Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
---
Hi,

I am not sure whether this regression has already been reported or
addressed. If it has, please feel free to drop this patch.
---
 drivers/gpu/drm/panel/panel-simple.c | 86 ++++++++++++++++++------------------
 1 file changed, 43 insertions(+), 43 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index da6b71b70a463400fcc45006788f87e97b0c148c..dc41789f6a53c78b928ff39291ab7219a2d835dd 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -623,49 +623,6 @@ static struct panel_simple *panel_simple_probe(struct device *dev)
 	if (IS_ERR(desc))
 		return ERR_CAST(desc);
 
-	panel = devm_drm_panel_alloc(dev, struct panel_simple, base,
-				     &panel_simple_funcs, desc->connector_type);
-	if (IS_ERR(panel))
-		return ERR_CAST(panel);
-
-	panel->desc = desc;
-
-	panel->supply = devm_regulator_get(dev, "power");
-	if (IS_ERR(panel->supply))
-		return ERR_CAST(panel->supply);
-
-	panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
-						     GPIOD_OUT_LOW);
-	if (IS_ERR(panel->enable_gpio))
-		return dev_err_cast_probe(dev, panel->enable_gpio,
-					  "failed to request GPIO\n");
-
-	err = of_drm_get_panel_orientation(dev->of_node, &panel->orientation);
-	if (err) {
-		dev_err(dev, "%pOF: failed to get orientation %d\n", dev->of_node, err);
-		return ERR_PTR(err);
-	}
-
-	ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
-	if (ddc) {
-		panel->ddc = of_find_i2c_adapter_by_node(ddc);
-		of_node_put(ddc);
-
-		if (!panel->ddc)
-			return ERR_PTR(-EPROBE_DEFER);
-	}
-
-	if (!of_device_is_compatible(dev->of_node, "panel-dpi") &&
-	    !of_get_display_timing(dev->of_node, "panel-timing", &dt))
-		panel_simple_parse_panel_timing_node(dev, panel, &dt);
-
-	if (desc->connector_type == DRM_MODE_CONNECTOR_LVDS) {
-		/* Optional data-mapping property for overriding bus format */
-		err = panel_simple_override_nondefault_lvds_datamapping(dev, panel);
-		if (err)
-			goto free_ddc;
-	}
-
 	connector_type = desc->connector_type;
 	/* Catch common mistakes for panels. */
 	switch (connector_type) {
@@ -720,6 +677,49 @@ static struct panel_simple *panel_simple_probe(struct device *dev)
 		break;
 	}
 
+	panel = devm_drm_panel_alloc(dev, struct panel_simple, base,
+				     &panel_simple_funcs, connector_type);
+	if (IS_ERR(panel))
+		return ERR_CAST(panel);
+
+	panel->desc = desc;
+
+	panel->supply = devm_regulator_get(dev, "power");
+	if (IS_ERR(panel->supply))
+		return ERR_CAST(panel->supply);
+
+	panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
+						     GPIOD_OUT_LOW);
+	if (IS_ERR(panel->enable_gpio))
+		return dev_err_cast_probe(dev, panel->enable_gpio,
+					  "failed to request GPIO\n");
+
+	err = of_drm_get_panel_orientation(dev->of_node, &panel->orientation);
+	if (err) {
+		dev_err(dev, "%pOF: failed to get orientation %d\n", dev->of_node, err);
+		return ERR_PTR(err);
+	}
+
+	ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
+	if (ddc) {
+		panel->ddc = of_find_i2c_adapter_by_node(ddc);
+		of_node_put(ddc);
+
+		if (!panel->ddc)
+			return ERR_PTR(-EPROBE_DEFER);
+	}
+
+	if (!of_device_is_compatible(dev->of_node, "panel-dpi") &&
+	    !of_get_display_timing(dev->of_node, "panel-timing", &dt))
+		panel_simple_parse_panel_timing_node(dev, panel, &dt);
+
+	if (desc->connector_type == DRM_MODE_CONNECTOR_LVDS) {
+		/* Optional data-mapping property for overriding bus format */
+		err = panel_simple_override_nondefault_lvds_datamapping(dev, panel);
+		if (err)
+			goto free_ddc;
+	}
+
 	dev_set_drvdata(dev, panel);
 
 	/*

---
base-commit: 88cbd8ac379cf5ce68b7efcfd4d1484a6871ee0b
change-id: 20251121-lcd_panel_connector_type_fix-f00fe3766a42

Best regards,
-- 
Ludovic Desroches <ludovic.desroches@microchip.com>

Re: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback

Posted by kernel test robot 1 week, 2 days ago

Hi Ludovic,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 88cbd8ac379cf5ce68b7efcfd4d1484a6871ee0b]

url:    https://github.com/intel-lab-lkp/linux/commits/Ludovic-Desroches/drm-panel-simple-restore-connector_type-fallback/20251121-212613
base:   88cbd8ac379cf5ce68b7efcfd4d1484a6871ee0b
patch link:    https://lore.kernel.org/r/20251121-lcd_panel_connector_type_fix-v1-1-fdbbef34a1a4%40microchip.com
patch subject: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback
config: arm-randconfig-002-20251123 (https://download.01.org/0day-ci/archive/20251123/202511230354.nHRvfjDz-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 9e9fe08b16ea2c4d9867fb4974edf2a3776d6ece)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251123/202511230354.nHRvfjDz-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511230354.nHRvfjDz-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/gpu/drm/panel/panel-simple.c:648:7: warning: variable 'panel' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
     648 |         case DRM_MODE_CONNECTOR_eDP:
         |              ^~~~~~~~~~~~~~~~~~~~~~
   include/uapi/drm/drm_mode.h:417:33: note: expanded from macro 'DRM_MODE_CONNECTOR_eDP'
     417 | #define DRM_MODE_CONNECTOR_eDP          14
         |                                         ^~
   drivers/gpu/drm/panel/panel-simple.c:749:6: note: uninitialized use occurs here
     749 |         if (panel->ddc)
         |             ^~~~~
   drivers/gpu/drm/panel/panel-simple.c:615:28: note: initialize the variable 'panel' to silence this warning
     615 |         struct panel_simple *panel;
         |                                   ^
         |                                    = NULL
   1 warning generated.


vim +/panel +648 drivers/gpu/drm/panel/panel-simple.c

47c08262f34e1c Maxime Ripard     2025-06-26  611  
47c08262f34e1c Maxime Ripard     2025-06-26  612  static struct panel_simple *panel_simple_probe(struct device *dev)
280921de7241ee Thierry Reding    2013-08-30  613  {
47c08262f34e1c Maxime Ripard     2025-06-26  614  	const struct panel_desc *desc;
280921de7241ee Thierry Reding    2013-08-30  615  	struct panel_simple *panel;
b8a2948fa2b3a5 Sean Paul         2019-07-11  616  	struct display_timing dt;
0fe1564bd61642 Sam Ravnborg      2019-12-07  617  	struct device_node *ddc;
9f069c6fbc7266 Sam Ravnborg      2020-07-26  618  	int connector_type;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  619  	u32 bus_flags;
280921de7241ee Thierry Reding    2013-08-30  620  	int err;
280921de7241ee Thierry Reding    2013-08-30  621  
47c08262f34e1c Maxime Ripard     2025-06-26  622  	desc = panel_simple_get_desc(dev);
47c08262f34e1c Maxime Ripard     2025-06-26  623  	if (IS_ERR(desc))
47c08262f34e1c Maxime Ripard     2025-06-26  624  		return ERR_CAST(desc);
47c08262f34e1c Maxime Ripard     2025-06-26  625  
9f069c6fbc7266 Sam Ravnborg      2020-07-26  626  	connector_type = desc->connector_type;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  627  	/* Catch common mistakes for panels. */
9f069c6fbc7266 Sam Ravnborg      2020-07-26  628  	switch (connector_type) {
ddb8e853dc8507 Sam Ravnborg      2020-07-26  629  	case 0:
ddb8e853dc8507 Sam Ravnborg      2020-07-26  630  		dev_warn(dev, "Specify missing connector_type\n");
9f069c6fbc7266 Sam Ravnborg      2020-07-26  631  		connector_type = DRM_MODE_CONNECTOR_DPI;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  632  		break;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  633  	case DRM_MODE_CONNECTOR_LVDS:
c4715837b02393 Laurent Pinchart  2020-06-30  634  		WARN_ON(desc->bus_flags &
c4715837b02393 Laurent Pinchart  2020-06-30  635  			~(DRM_BUS_FLAG_DE_LOW |
c4715837b02393 Laurent Pinchart  2020-06-30  636  			  DRM_BUS_FLAG_DE_HIGH |
c4715837b02393 Laurent Pinchart  2020-06-30  637  			  DRM_BUS_FLAG_DATA_MSB_TO_LSB |
c4715837b02393 Laurent Pinchart  2020-06-30  638  			  DRM_BUS_FLAG_DATA_LSB_TO_MSB));
1185c406f11a49 Laurent Pinchart  2020-06-30  639  		WARN_ON(desc->bus_format != MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
1185c406f11a49 Laurent Pinchart  2020-06-30  640  			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_SPWG &&
1185c406f11a49 Laurent Pinchart  2020-06-30  641  			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA);
1185c406f11a49 Laurent Pinchart  2020-06-30  642  		WARN_ON(desc->bus_format == MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
1185c406f11a49 Laurent Pinchart  2020-06-30  643  			desc->bpc != 6);
1185c406f11a49 Laurent Pinchart  2020-06-30  644  		WARN_ON((desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_SPWG ||
1185c406f11a49 Laurent Pinchart  2020-06-30  645  			 desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA) &&
1185c406f11a49 Laurent Pinchart  2020-06-30  646  			desc->bpc != 8);
ddb8e853dc8507 Sam Ravnborg      2020-07-26  647  		break;
ddb8e853dc8507 Sam Ravnborg      2020-07-26 @648  	case DRM_MODE_CONNECTOR_eDP:
5f04e7ce392db9 Douglas Anderson  2021-09-14  649  		dev_warn(dev, "eDP panels moved to panel-edp\n");
5f04e7ce392db9 Douglas Anderson  2021-09-14  650  		err = -EINVAL;
5f04e7ce392db9 Douglas Anderson  2021-09-14  651  		goto free_ddc;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  652  	case DRM_MODE_CONNECTOR_DSI:
ddb8e853dc8507 Sam Ravnborg      2020-07-26  653  		if (desc->bpc != 6 && desc->bpc != 8)
ddb8e853dc8507 Sam Ravnborg      2020-07-26  654  			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
ddb8e853dc8507 Sam Ravnborg      2020-07-26  655  		break;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  656  	case DRM_MODE_CONNECTOR_DPI:
ddb8e853dc8507 Sam Ravnborg      2020-07-26  657  		bus_flags = DRM_BUS_FLAG_DE_LOW |
ddb8e853dc8507 Sam Ravnborg      2020-07-26  658  			    DRM_BUS_FLAG_DE_HIGH |
ddb8e853dc8507 Sam Ravnborg      2020-07-26  659  			    DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE |
ddb8e853dc8507 Sam Ravnborg      2020-07-26  660  			    DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE |
ddb8e853dc8507 Sam Ravnborg      2020-07-26  661  			    DRM_BUS_FLAG_DATA_MSB_TO_LSB |
ddb8e853dc8507 Sam Ravnborg      2020-07-26  662  			    DRM_BUS_FLAG_DATA_LSB_TO_MSB |
ddb8e853dc8507 Sam Ravnborg      2020-07-26  663  			    DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE |
ddb8e853dc8507 Sam Ravnborg      2020-07-26  664  			    DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  665  		if (desc->bus_flags & ~bus_flags)
ddb8e853dc8507 Sam Ravnborg      2020-07-26  666  			dev_warn(dev, "Unexpected bus_flags(%d)\n", desc->bus_flags & ~bus_flags);
ddb8e853dc8507 Sam Ravnborg      2020-07-26  667  		if (!(desc->bus_flags & bus_flags))
ddb8e853dc8507 Sam Ravnborg      2020-07-26  668  			dev_warn(dev, "Specify missing bus_flags\n");
ddb8e853dc8507 Sam Ravnborg      2020-07-26  669  		if (desc->bus_format == 0)
ddb8e853dc8507 Sam Ravnborg      2020-07-26  670  			dev_warn(dev, "Specify missing bus_format\n");
ddb8e853dc8507 Sam Ravnborg      2020-07-26  671  		if (desc->bpc != 6 && desc->bpc != 8)
ddb8e853dc8507 Sam Ravnborg      2020-07-26  672  			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
ddb8e853dc8507 Sam Ravnborg      2020-07-26  673  		break;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  674  	default:
ddb8e853dc8507 Sam Ravnborg      2020-07-26  675  		dev_warn(dev, "Specify a valid connector_type: %d\n", desc->connector_type);
9f069c6fbc7266 Sam Ravnborg      2020-07-26  676  		connector_type = DRM_MODE_CONNECTOR_DPI;
ddb8e853dc8507 Sam Ravnborg      2020-07-26  677  		break;
1185c406f11a49 Laurent Pinchart  2020-06-30  678  	}
c4715837b02393 Laurent Pinchart  2020-06-30  679  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  680  	panel = devm_drm_panel_alloc(dev, struct panel_simple, base,
2803eb4aeb2702 Ludovic Desroches 2025-11-21  681  				     &panel_simple_funcs, connector_type);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  682  	if (IS_ERR(panel))
2803eb4aeb2702 Ludovic Desroches 2025-11-21  683  		return ERR_CAST(panel);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  684  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  685  	panel->desc = desc;
2803eb4aeb2702 Ludovic Desroches 2025-11-21  686  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  687  	panel->supply = devm_regulator_get(dev, "power");
2803eb4aeb2702 Ludovic Desroches 2025-11-21  688  	if (IS_ERR(panel->supply))
2803eb4aeb2702 Ludovic Desroches 2025-11-21  689  		return ERR_CAST(panel->supply);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  690  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  691  	panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
2803eb4aeb2702 Ludovic Desroches 2025-11-21  692  						     GPIOD_OUT_LOW);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  693  	if (IS_ERR(panel->enable_gpio))
2803eb4aeb2702 Ludovic Desroches 2025-11-21  694  		return dev_err_cast_probe(dev, panel->enable_gpio,
2803eb4aeb2702 Ludovic Desroches 2025-11-21  695  					  "failed to request GPIO\n");
2803eb4aeb2702 Ludovic Desroches 2025-11-21  696  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  697  	err = of_drm_get_panel_orientation(dev->of_node, &panel->orientation);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  698  	if (err) {
2803eb4aeb2702 Ludovic Desroches 2025-11-21  699  		dev_err(dev, "%pOF: failed to get orientation %d\n", dev->of_node, err);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  700  		return ERR_PTR(err);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  701  	}
2803eb4aeb2702 Ludovic Desroches 2025-11-21  702  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  703  	ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  704  	if (ddc) {
2803eb4aeb2702 Ludovic Desroches 2025-11-21  705  		panel->ddc = of_find_i2c_adapter_by_node(ddc);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  706  		of_node_put(ddc);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  707  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  708  		if (!panel->ddc)
2803eb4aeb2702 Ludovic Desroches 2025-11-21  709  			return ERR_PTR(-EPROBE_DEFER);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  710  	}
2803eb4aeb2702 Ludovic Desroches 2025-11-21  711  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  712  	if (!of_device_is_compatible(dev->of_node, "panel-dpi") &&
2803eb4aeb2702 Ludovic Desroches 2025-11-21  713  	    !of_get_display_timing(dev->of_node, "panel-timing", &dt))
2803eb4aeb2702 Ludovic Desroches 2025-11-21  714  		panel_simple_parse_panel_timing_node(dev, panel, &dt);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  715  
2803eb4aeb2702 Ludovic Desroches 2025-11-21  716  	if (desc->connector_type == DRM_MODE_CONNECTOR_LVDS) {
2803eb4aeb2702 Ludovic Desroches 2025-11-21  717  		/* Optional data-mapping property for overriding bus format */
2803eb4aeb2702 Ludovic Desroches 2025-11-21  718  		err = panel_simple_override_nondefault_lvds_datamapping(dev, panel);
2803eb4aeb2702 Ludovic Desroches 2025-11-21  719  		if (err)
2803eb4aeb2702 Ludovic Desroches 2025-11-21  720  			goto free_ddc;
2803eb4aeb2702 Ludovic Desroches 2025-11-21  721  	}
2803eb4aeb2702 Ludovic Desroches 2025-11-21  722  
3235b0f20a0a41 Douglas Anderson  2021-04-16  723  	dev_set_drvdata(dev, panel);
3235b0f20a0a41 Douglas Anderson  2021-04-16  724  
3235b0f20a0a41 Douglas Anderson  2021-04-16  725  	/*
3235b0f20a0a41 Douglas Anderson  2021-04-16  726  	 * We use runtime PM for prepare / unprepare since those power the panel
3235b0f20a0a41 Douglas Anderson  2021-04-16  727  	 * on and off and those can be very slow operations. This is important
3235b0f20a0a41 Douglas Anderson  2021-04-16  728  	 * to optimize powering the panel on briefly to read the EDID before
3235b0f20a0a41 Douglas Anderson  2021-04-16  729  	 * fully enabling the panel.
3235b0f20a0a41 Douglas Anderson  2021-04-16  730  	 */
3235b0f20a0a41 Douglas Anderson  2021-04-16  731  	pm_runtime_enable(dev);
3235b0f20a0a41 Douglas Anderson  2021-04-16  732  	pm_runtime_set_autosuspend_delay(dev, 1000);
3235b0f20a0a41 Douglas Anderson  2021-04-16  733  	pm_runtime_use_autosuspend(dev);
3235b0f20a0a41 Douglas Anderson  2021-04-16  734  
0fe1564bd61642 Sam Ravnborg      2019-12-07  735  	err = drm_panel_of_backlight(&panel->base);
d9e74da2f1fc42 Alexander Stein   2022-06-21  736  	if (err) {
d9e74da2f1fc42 Alexander Stein   2022-06-21  737  		dev_err_probe(dev, err, "Could not find backlight\n");
70e12560126685 Douglas Anderson  2021-04-23  738  		goto disable_pm_runtime;
d9e74da2f1fc42 Alexander Stein   2022-06-21  739  	}
0fe1564bd61642 Sam Ravnborg      2019-12-07  740  
c3ee8c65f63799 Bernard Zhao      2020-08-01  741  	drm_panel_add(&panel->base);
280921de7241ee Thierry Reding    2013-08-30  742  
921c41e509746a Maxime Ripard     2025-06-26  743  	return panel;
280921de7241ee Thierry Reding    2013-08-30  744  
70e12560126685 Douglas Anderson  2021-04-23  745  disable_pm_runtime:
a596fcd9cbc781 Douglas Anderson  2021-05-17  746  	pm_runtime_dont_use_autosuspend(dev);
70e12560126685 Douglas Anderson  2021-04-23  747  	pm_runtime_disable(dev);
280921de7241ee Thierry Reding    2013-08-30  748  free_ddc:
5f04e7ce392db9 Douglas Anderson  2021-09-14  749  	if (panel->ddc)
280921de7241ee Thierry Reding    2013-08-30  750  		put_device(&panel->ddc->dev);
280921de7241ee Thierry Reding    2013-08-30  751  
921c41e509746a Maxime Ripard     2025-06-26  752  	return ERR_PTR(err);
280921de7241ee Thierry Reding    2013-08-30  753  }
280921de7241ee Thierry Reding    2013-08-30  754  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback

Posted by Neil Armstrong 5 days, 16 hours ago

Hi,

On 11/22/25 21:26, kernel test robot wrote:
> Hi Ludovic,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on 88cbd8ac379cf5ce68b7efcfd4d1484a6871ee0b]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Ludovic-Desroches/drm-panel-simple-restore-connector_type-fallback/20251121-212613
> base:   88cbd8ac379cf5ce68b7efcfd4d1484a6871ee0b
> patch link:    https://lore.kernel.org/r/20251121-lcd_panel_connector_type_fix-v1-1-fdbbef34a1a4%40microchip.com
> patch subject: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback
> config: arm-randconfig-002-20251123 (https://download.01.org/0day-ci/archive/20251123/202511230354.nHRvfjDz-lkp@intel.com/config)
> compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 9e9fe08b16ea2c4d9867fb4974edf2a3776d6ece)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251123/202511230354.nHRvfjDz-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202511230354.nHRvfjDz-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>>> drivers/gpu/drm/panel/panel-simple.c:648:7: warning: variable 'panel' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
>       648 |         case DRM_MODE_CONNECTOR_eDP:
>           |              ^~~~~~~~~~~~~~~~~~~~~~
>     include/uapi/drm/drm_mode.h:417:33: note: expanded from macro 'DRM_MODE_CONNECTOR_eDP'
>       417 | #define DRM_MODE_CONNECTOR_eDP          14
>           |                                         ^~
>     drivers/gpu/drm/panel/panel-simple.c:749:6: note: uninitialized use occurs here
>       749 |         if (panel->ddc)
>           |             ^~~~~
>     drivers/gpu/drm/panel/panel-simple.c:615:28: note: initialize the variable 'panel' to silence this warning
>       615 |         struct panel_simple *panel;
>           |                                   ^
>           |                                    = NULL
>     1 warning generated.
> 
> 
> vim +/panel +648 drivers/gpu/drm/panel/panel-simple.c
> 
> 47c08262f34e1c Maxime Ripard     2025-06-26  611
> 47c08262f34e1c Maxime Ripard     2025-06-26  612  static struct panel_simple *panel_simple_probe(struct device *dev)
> 280921de7241ee Thierry Reding    2013-08-30  613  {
> 47c08262f34e1c Maxime Ripard     2025-06-26  614  	const struct panel_desc *desc;
> 280921de7241ee Thierry Reding    2013-08-30  615  	struct panel_simple *panel;
> b8a2948fa2b3a5 Sean Paul         2019-07-11  616  	struct display_timing dt;
> 0fe1564bd61642 Sam Ravnborg      2019-12-07  617  	struct device_node *ddc;
> 9f069c6fbc7266 Sam Ravnborg      2020-07-26  618  	int connector_type;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  619  	u32 bus_flags;
> 280921de7241ee Thierry Reding    2013-08-30  620  	int err;
> 280921de7241ee Thierry Reding    2013-08-30  621
> 47c08262f34e1c Maxime Ripard     2025-06-26  622  	desc = panel_simple_get_desc(dev);
> 47c08262f34e1c Maxime Ripard     2025-06-26  623  	if (IS_ERR(desc))
> 47c08262f34e1c Maxime Ripard     2025-06-26  624  		return ERR_CAST(desc);
> 47c08262f34e1c Maxime Ripard     2025-06-26  625
> 9f069c6fbc7266 Sam Ravnborg      2020-07-26  626  	connector_type = desc->connector_type;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  627  	/* Catch common mistakes for panels. */
> 9f069c6fbc7266 Sam Ravnborg      2020-07-26  628  	switch (connector_type) {
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  629  	case 0:
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  630  		dev_warn(dev, "Specify missing connector_type\n");
> 9f069c6fbc7266 Sam Ravnborg      2020-07-26  631  		connector_type = DRM_MODE_CONNECTOR_DPI;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  632  		break;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  633  	case DRM_MODE_CONNECTOR_LVDS:
> c4715837b02393 Laurent Pinchart  2020-06-30  634  		WARN_ON(desc->bus_flags &
> c4715837b02393 Laurent Pinchart  2020-06-30  635  			~(DRM_BUS_FLAG_DE_LOW |
> c4715837b02393 Laurent Pinchart  2020-06-30  636  			  DRM_BUS_FLAG_DE_HIGH |
> c4715837b02393 Laurent Pinchart  2020-06-30  637  			  DRM_BUS_FLAG_DATA_MSB_TO_LSB |
> c4715837b02393 Laurent Pinchart  2020-06-30  638  			  DRM_BUS_FLAG_DATA_LSB_TO_MSB));
> 1185c406f11a49 Laurent Pinchart  2020-06-30  639  		WARN_ON(desc->bus_format != MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
> 1185c406f11a49 Laurent Pinchart  2020-06-30  640  			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_SPWG &&
> 1185c406f11a49 Laurent Pinchart  2020-06-30  641  			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA);
> 1185c406f11a49 Laurent Pinchart  2020-06-30  642  		WARN_ON(desc->bus_format == MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
> 1185c406f11a49 Laurent Pinchart  2020-06-30  643  			desc->bpc != 6);
> 1185c406f11a49 Laurent Pinchart  2020-06-30  644  		WARN_ON((desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_SPWG ||
> 1185c406f11a49 Laurent Pinchart  2020-06-30  645  			 desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA) &&
> 1185c406f11a49 Laurent Pinchart  2020-06-30  646  			desc->bpc != 8);
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  647  		break;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26 @648  	case DRM_MODE_CONNECTOR_eDP:
> 5f04e7ce392db9 Douglas Anderson  2021-09-14  649  		dev_warn(dev, "eDP panels moved to panel-edp\n");
> 5f04e7ce392db9 Douglas Anderson  2021-09-14  650  		err = -EINVAL;
> 5f04e7ce392db9 Douglas Anderson  2021-09-14  651  		goto free_ddc;

The error is legitimate, here we'll try to access panel->ddc, but the panel isn't allocated.

Please fix this.

Neil

> ddb8e853dc8507 Sam Ravnborg      2020-07-26  652  	case DRM_MODE_CONNECTOR_DSI:
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  653  		if (desc->bpc != 6 && desc->bpc != 8)
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  654  			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  655  		break;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  656  	case DRM_MODE_CONNECTOR_DPI:
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  657  		bus_flags = DRM_BUS_FLAG_DE_LOW |
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  658  			    DRM_BUS_FLAG_DE_HIGH |
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  659  			    DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE |
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  660  			    DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE |
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  661  			    DRM_BUS_FLAG_DATA_MSB_TO_LSB |
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  662  			    DRM_BUS_FLAG_DATA_LSB_TO_MSB |
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  663  			    DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE |
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  664  			    DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  665  		if (desc->bus_flags & ~bus_flags)
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  666  			dev_warn(dev, "Unexpected bus_flags(%d)\n", desc->bus_flags & ~bus_flags);
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  667  		if (!(desc->bus_flags & bus_flags))
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  668  			dev_warn(dev, "Specify missing bus_flags\n");
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  669  		if (desc->bus_format == 0)
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  670  			dev_warn(dev, "Specify missing bus_format\n");
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  671  		if (desc->bpc != 6 && desc->bpc != 8)
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  672  			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  673  		break;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  674  	default:
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  675  		dev_warn(dev, "Specify a valid connector_type: %d\n", desc->connector_type);
> 9f069c6fbc7266 Sam Ravnborg      2020-07-26  676  		connector_type = DRM_MODE_CONNECTOR_DPI;
> ddb8e853dc8507 Sam Ravnborg      2020-07-26  677  		break;
> 1185c406f11a49 Laurent Pinchart  2020-06-30  678  	}
> c4715837b02393 Laurent Pinchart  2020-06-30  679
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  680  	panel = devm_drm_panel_alloc(dev, struct panel_simple, base,
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  681  				     &panel_simple_funcs, connector_type);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  682  	if (IS_ERR(panel))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  683  		return ERR_CAST(panel);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  684
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  685  	panel->desc = desc;
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  686
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  687  	panel->supply = devm_regulator_get(dev, "power");
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  688  	if (IS_ERR(panel->supply))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  689  		return ERR_CAST(panel->supply);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  690
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  691  	panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  692  						     GPIOD_OUT_LOW);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  693  	if (IS_ERR(panel->enable_gpio))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  694  		return dev_err_cast_probe(dev, panel->enable_gpio,
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  695  					  "failed to request GPIO\n");
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  696
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  697  	err = of_drm_get_panel_orientation(dev->of_node, &panel->orientation);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  698  	if (err) {
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  699  		dev_err(dev, "%pOF: failed to get orientation %d\n", dev->of_node, err);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  700  		return ERR_PTR(err);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  701  	}
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  702
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  703  	ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  704  	if (ddc) {
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  705  		panel->ddc = of_find_i2c_adapter_by_node(ddc);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  706  		of_node_put(ddc);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  707
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  708  		if (!panel->ddc)
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  709  			return ERR_PTR(-EPROBE_DEFER);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  710  	}
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  711
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  712  	if (!of_device_is_compatible(dev->of_node, "panel-dpi") &&
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  713  	    !of_get_display_timing(dev->of_node, "panel-timing", &dt))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  714  		panel_simple_parse_panel_timing_node(dev, panel, &dt);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  715
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  716  	if (desc->connector_type == DRM_MODE_CONNECTOR_LVDS) {
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  717  		/* Optional data-mapping property for overriding bus format */
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  718  		err = panel_simple_override_nondefault_lvds_datamapping(dev, panel);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  719  		if (err)
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  720  			goto free_ddc;
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  721  	}
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21  722
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  723  	dev_set_drvdata(dev, panel);
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  724
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  725  	/*
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  726  	 * We use runtime PM for prepare / unprepare since those power the panel
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  727  	 * on and off and those can be very slow operations. This is important
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  728  	 * to optimize powering the panel on briefly to read the EDID before
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  729  	 * fully enabling the panel.
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  730  	 */
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  731  	pm_runtime_enable(dev);
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  732  	pm_runtime_set_autosuspend_delay(dev, 1000);
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  733  	pm_runtime_use_autosuspend(dev);
> 3235b0f20a0a41 Douglas Anderson  2021-04-16  734
> 0fe1564bd61642 Sam Ravnborg      2019-12-07  735  	err = drm_panel_of_backlight(&panel->base);
> d9e74da2f1fc42 Alexander Stein   2022-06-21  736  	if (err) {
> d9e74da2f1fc42 Alexander Stein   2022-06-21  737  		dev_err_probe(dev, err, "Could not find backlight\n");
> 70e12560126685 Douglas Anderson  2021-04-23  738  		goto disable_pm_runtime;
> d9e74da2f1fc42 Alexander Stein   2022-06-21  739  	}
> 0fe1564bd61642 Sam Ravnborg      2019-12-07  740
> c3ee8c65f63799 Bernard Zhao      2020-08-01  741  	drm_panel_add(&panel->base);
> 280921de7241ee Thierry Reding    2013-08-30  742
> 921c41e509746a Maxime Ripard     2025-06-26  743  	return panel;
> 280921de7241ee Thierry Reding    2013-08-30  744
> 70e12560126685 Douglas Anderson  2021-04-23  745  disable_pm_runtime:
> a596fcd9cbc781 Douglas Anderson  2021-05-17  746  	pm_runtime_dont_use_autosuspend(dev);
> 70e12560126685 Douglas Anderson  2021-04-23  747  	pm_runtime_disable(dev);
> 280921de7241ee Thierry Reding    2013-08-30  748  free_ddc:
> 5f04e7ce392db9 Douglas Anderson  2021-09-14  749  	if (panel->ddc)
> 280921de7241ee Thierry Reding    2013-08-30  750  		put_device(&panel->ddc->dev);
> 280921de7241ee Thierry Reding    2013-08-30  751
> 921c41e509746a Maxime Ripard     2025-06-26  752  	return ERR_PTR(err);
> 280921de7241ee Thierry Reding    2013-08-30  753  }
> 280921de7241ee Thierry Reding    2013-08-30  754
>

Re: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback

Posted by Dmitry Baryshkov 1 week, 3 days ago

On Fri, Nov 21, 2025 at 02:20:48PM +0100, Ludovic Desroches wrote:
> The switch from devm_kzalloc() + drm_panel_init() to
> devm_drm_panel_alloc() introduced a regression.
> 
> Several panel descriptors do not set connector_type. For those panels,
> panel_simple_probe() used to compute a connector type (currently DPI as a
> fallback) and pass that value to drm_panel_init(). After the conversion
> to devm_drm_panel_alloc(), the call unconditionally used
> desc->connector_type instead, ignoring the computed fallback and
> potentially passing DRM_MODE_CONNECTOR_Unknown, which
> drm_panel_bridge_add() does not allow.
> 
> Move the connector_type validation / fallback logic before the
> devm_drm_panel_alloc() call and pass the computed connector_type to
> devm_drm_panel_alloc(), so panels without an explicit connector_type
> once again get the DPI default.
> 
> Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
> Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
> ---
> Hi,
> 
> I am not sure whether this regression has already been reported or
> addressed. If it has, please feel free to drop this patch.

Would it be better to fix those panels instead? In the end, the panel
usually has only one bus.

> ---
>  drivers/gpu/drm/panel/panel-simple.c | 86 ++++++++++++++++++------------------
>  1 file changed, 43 insertions(+), 43 deletions(-)

-- 
With best wishes
Dmitry

Re: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback

Posted by Ludovic.Desroches@microchip.com 5 days, 17 hours ago

On 11/21/25 23:52, Dmitry Baryshkov wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Fri, Nov 21, 2025 at 02:20:48PM +0100, Ludovic Desroches wrote:
>> The switch from devm_kzalloc() + drm_panel_init() to
>> devm_drm_panel_alloc() introduced a regression.
>>
>> Several panel descriptors do not set connector_type. For those panels,
>> panel_simple_probe() used to compute a connector type (currently DPI as a
>> fallback) and pass that value to drm_panel_init(). After the conversion
>> to devm_drm_panel_alloc(), the call unconditionally used
>> desc->connector_type instead, ignoring the computed fallback and
>> potentially passing DRM_MODE_CONNECTOR_Unknown, which
>> drm_panel_bridge_add() does not allow.
>>
>> Move the connector_type validation / fallback logic before the
>> devm_drm_panel_alloc() call and pass the computed connector_type to
>> devm_drm_panel_alloc(), so panels without an explicit connector_type
>> once again get the DPI default.
>>
>> Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
>> Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
>> ---
>> Hi,
>>
>> I am not sure whether this regression has already been reported or
>> addressed. If it has, please feel free to drop this patch.
> 
> Would it be better to fix those panels instead? In the end, the panel
> usually has only one bus.

I don’t have a strong opinion on this point. I don’t know if there are 
any historical reasons behind all this.

Regards,
Ludovic

> 
>> ---
>>   drivers/gpu/drm/panel/panel-simple.c | 86 ++++++++++++++++++------------------
>>   1 file changed, 43 insertions(+), 43 deletions(-)
> 
> --
> With best wishes
> Dmitry

Re: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback

Posted by Maxime Ripard 1 week, 3 days ago

On Fri, 21 Nov 2025 14:20:48 +0100, Ludovic Desroches wrote:
> The switch from devm_kzalloc() + drm_panel_init() to
> devm_drm_panel_alloc() introduced a regression.
> 
> Several panel descriptors do not set connector_type. For those panels,
> panel_simple_probe() used to compute a connector type (currently DPI as a
> 
> [ ... ]

Reviewed-by: Maxime Ripard <mripard@kernel.org>

Thanks!
Maxime