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Message-Id: <20250624-b4-simple-panel-regression-v1-1-a5adf92a7c17@redhat.com>
Date: Tue, 24 Jun 2025 15:13:05 -0500
From: Anusha Srivatsa <asrivats@...hat.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
Jessica Zhang <quic_jesszhan@...cinc.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Francesco Dolcini <francesco@...cini.it>,
Anusha Srivatsa <asrivats@...hat.com>
Subject: [PATCH] panel/simple-simple: Identify simple DPI panels using
.compatible field
Currently driver is checking for desc == &panel_dpi to do the DPI
specific panel desc allocations. This looks hacky.
The panel allocation in panel_simple_probe() breaks due to not having
the desc for DPI scenario. This patch does the following:
- Rename panel_dpi_probe() to panel_dpi_get_desc() and call it before
panel allocation. panel_dpi_get_desc() returns a panel desc unlike
panel_dpi_probe() which returned an int. This way driver has a known
connector type while allocating the panel.
- panel_dpi_get_desc() returns a panel desc
- Add a simple helper is_panel_dpi() to identify a simple DPI panel from
a simple panel based on .compatible field
Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
Suggested-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
Suggested-by: Maxime Ripard <mripard@...nel.org>
Cc: Francesco Dolcini <francesco@...cini.it>
Cc: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: Maxime Ripard <mripard@...nel.org>
Signed-off-by: Anusha Srivatsa <asrivats@...hat.com>
---
Seeing the below trace due to the changes introduced by:
Commit de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
[ 12.089274] ------------[ cut here ]------------
[ 12.089303] WARNING: CPU: 0 PID: 96 at drivers/gpu/drm/bridge/panel.c:377 devm_drm_of_get_bridge+0xac/0xb8
[ 12.130808] Modules linked in: v4l2_jpeg pwm_imx27(+) imx_vdoa gpu_sched panel_simple imx6_media(C) imx_media_common
(C) videobuf2_dma_contig pwm_bl gpio_keys v4l2_mem2mem fuse ipv6 autofs4
[ 12.147774] CPU: 0 UID: 0 PID: 96 Comm: kworker/u8:3 Tainted: G C 6.16.0-rc1+ #1 PREEMPT
[ 12.157446] Tainted: [C]=CRAP
[ 12.160418] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
[ 12.166953] Workqueue: events_unbound deferred_probe_work_func
[ 12.172805] Call trace:
[ 12.172815] unwind_backtrace from show_stack+0x10/0x14
[ 12.180598] show_stack from dump_stack_lvl+0x68/0x74
[ 12.185674] dump_stack_lvl from __warn+0x7c/0xe0
[ 12.190407] __warn from warn_slowpath_fmt+0x1b8/0x1c0
[ 12.195567] warn_slowpath_fmt from devm_drm_of_get_bridge+0xac/0xb8
[ 12.201949] devm_drm_of_get_bridge from imx_pd_probe+0x58/0x164
[ 12.207976] imx_pd_probe from platform_probe+0x5c/0xb0
[ 12.213220] platform_probe from really_probe+0xd0/0x3a4
[ 12.218551] really_probe from __driver_probe_device+0x8c/0x1d4
[ 12.224486] __driver_probe_device from driver_probe_device+0x30/0xc0
[ 12.230942] driver_probe_device from __device_attach_driver+0x98/0x10c
[ 12.237572] __device_attach_driver from bus_for_each_drv+0x90/0xe4
[ 12.243854] bus_for_each_drv from __device_attach+0xa8/0x1c8
[ 12.249614] __device_attach from bus_probe_device+0x88/0x8c
[ 12.255285] bus_probe_device from deferred_probe_work_func+0x8c/0xcc
[ 12.261739] deferred_probe_work_func from process_one_work+0x154/0x2dc
[ 12.268371] process_one_work from worker_thread+0x250/0x3f0
[ 12.274043] worker_thread from kthread+0x12c/0x24c
[ 12.278940] kthread from ret_from_fork+0x14/0x28
[ 12.283660] Exception stack(0xd0be9fb0 to 0xd0be9ff8)
[ 12.288720] 9fa0: 00000000 00000000 00000000 00000000
[ 12.296906] 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 12.305089] 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 12.312050] ---[ end trace 0000000000000000 ]---
---
drivers/gpu/drm/panel/panel-simple.c | 38 +++++++++++++++++++++---------------
1 file changed, 22 insertions(+), 16 deletions(-)
diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 0a3b26bb4d731c54614e24e38018c308acd5367a..2e6fd545100388a9d53183a5621e7b8fdb4148ae 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -26,6 +26,7 @@
#include <linux/i2c.h>
#include <linux/media-bus-format.h>
#include <linux/module.h>
+#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
@@ -432,8 +433,7 @@ static const struct drm_panel_funcs panel_simple_funcs = {
static struct panel_desc panel_dpi;
-static int panel_dpi_probe(struct device *dev,
- struct panel_simple *panel)
+static struct panel_desc *panel_dpi_get_desc(struct device *dev)
{
struct display_timing *timing;
const struct device_node *np;
@@ -445,17 +445,17 @@ static int panel_dpi_probe(struct device *dev,
np = dev->of_node;
desc = devm_kzalloc(dev, sizeof(*desc), GFP_KERNEL);
if (!desc)
- return -ENOMEM;
+ return NULL;
timing = devm_kzalloc(dev, sizeof(*timing), GFP_KERNEL);
if (!timing)
- return -ENOMEM;
+ return NULL;
ret = of_get_display_timing(np, "panel-timing", timing);
if (ret < 0) {
dev_err(dev, "%pOF: no panel-timing node found for \"panel-dpi\" binding\n",
np);
- return ret;
+ return NULL;
}
desc->timings = timing;
@@ -473,9 +473,7 @@ static int panel_dpi_probe(struct device *dev,
/* We do not know the connector for the DT node, so guess it */
desc->connector_type = DRM_MODE_CONNECTOR_DPI;
- panel->desc = desc;
-
- return 0;
+ return desc;
}
#define PANEL_SIMPLE_BOUNDS_CHECK(to_check, bounds, field) \
@@ -570,6 +568,15 @@ static int panel_simple_override_nondefault_lvds_datamapping(struct device *dev,
return 0;
}
+static bool is_panel_dpi(struct device *dev)
+{
+ const struct of_device_id *match;
+
+ match = of_match_device(dev->driver->of_match_table, dev);
+
+ return strcmp(match->compatible, "panel_dpi");
+}
+
static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
{
struct panel_simple *panel;
@@ -579,6 +586,10 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
u32 bus_flags;
int err;
+ /* Is this simple panel a DPI panel */
+ if (is_panel_dpi(dev))
+ desc = panel_dpi_get_desc(dev);
+
panel = devm_drm_panel_alloc(dev, struct panel_simple, base,
&panel_simple_funcs, desc->connector_type);
if (IS_ERR(panel))
@@ -611,16 +622,11 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
return -EPROBE_DEFER;
}
- if (desc == &panel_dpi) {
- /* Handle the generic panel-dpi binding */
- err = panel_dpi_probe(dev, panel);
- if (err)
- goto free_ddc;
- desc = panel->desc;
- } else {
+ if (is_panel_dpi(dev))
+ goto free_ddc;
+ else
if (!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 */
---
base-commit: 10357824151262636fda879845f8b64553541106
change-id: 20250624-b4-simple-panel-regression-8ae3ba282fe2
Best regards,
--
Anusha Srivatsa <asrivats@...hat.com>
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