Add a debugfs file, so you can test drm_panic without freezing
your machine. This is unsafe, and should be enabled only for
developer or tester.
To display the drm_panic screen on the device 0:
echo 1 > /sys/kernel/debug/dri/0/drm_panic_plane_0
v9:
* Create a debugfs file for each plane in the device's debugfs
directory. This allows to test for each plane of each GPU
independently.
Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
---
drivers/gpu/drm/Kconfig | 9 ++++++++
drivers/gpu/drm/drm_panic.c | 43 ++++++++++++++++++++++++++++++++++++-
2 files changed, 51 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index f07ca38d3f98..6e41fbd16b3d 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -125,6 +125,15 @@ config DRM_PANIC_BACKGROUND_COLOR
depends on DRM_PANIC
default 0x000000
+config DRM_PANIC_DEBUG
+ bool "Add a debug fs entry to trigger drm_panic"
+ depends on DRM_PANIC && DEBUG_FS
+ help
+ Add dri/[device]/drm_panic_plane_x in the kernel debugfs, to force the
+ panic handler to write the panic message to this plane scanout buffer.
+ This is unsafe and should not be enabled on a production build.
+ If in doubt, say "N".
+
config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
bool "Enable refcount backtrace history in the DP MST helpers"
depends on STACKTRACE_SUPPORT
diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
index 2c3b2fffe659..cd2c7c2d1c59 100644
--- a/drivers/gpu/drm/drm_panic.c
+++ b/drivers/gpu/drm/drm_panic.c
@@ -493,6 +493,45 @@ static void drm_panic(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason)
draw_panic_plane(plane);
}
+
+/*
+ * DEBUG FS, This is currently unsafe.
+ * Create one file per plane, so it's possible to debug one plane at a time.
+ */
+#ifdef CONFIG_DRM_PANIC_DEBUG
+#include <linux/debugfs.h>
+
+static ssize_t debugfs_trigger_write(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ bool run;
+
+ if (kstrtobool_from_user(user_buf, count, &run) == 0 && run) {
+ struct drm_plane *plane = file->private_data;
+
+ draw_panic_plane(plane);
+ }
+ return count;
+}
+
+static const struct file_operations dbg_drm_panic_ops = {
+ .owner = THIS_MODULE,
+ .write = debugfs_trigger_write,
+ .open = simple_open,
+};
+
+static void debugfs_register_plane(struct drm_plane *plane, int index)
+{
+ char fname[32];
+
+ snprintf(fname, 32, "drm_panic_plane_%d", index);
+ debugfs_create_file(fname, 0200, plane->dev->debugfs_root,
+ plane, &dbg_drm_panic_ops);
+}
+#else
+static void debugfs_register_plane(struct drm_plane *plane, int index) {}
+#endif /* CONFIG_DRM_PANIC_DEBUG */
+
/**
* drm_panic_register() - Initialize DRM panic for a device
* @dev: the drm device on which the panic screen will be displayed.
@@ -512,8 +551,10 @@ void drm_panic_register(struct drm_device *dev)
plane->kmsg_panic.max_reason = KMSG_DUMP_PANIC;
if (kmsg_dump_register(&plane->kmsg_panic))
drm_warn(dev, "Failed to register panic handler\n");
- else
+ else {
+ debugfs_register_plane(plane, registered_plane);
registered_plane++;
+ }
}
if (registered_plane)
drm_info(dev, "Registered %d planes with drm panic\n", registered_plane);
--
2.44.0
