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drm/panic: Add debugfs entry to test without triggering panic.

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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@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240409163432.352518-5-jfalempe@redhat.com
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Jocelyn Falempe
2024-04-09 18:30:43 +02:00
parent 9544309775
commit 813ca3aa8f
2 changed files with 52 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/gpu/drm/Kconfig
View File

@@ -127,6 +127,15 @@ 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

44
drivers/gpu/drm/drm_panic.c
View File

@@ -496,6 +496,46 @@ 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.
* TODO: It would be better to emulate an NMI context.
*/
#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.
@@ -515,8 +555,10 @@ 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);