On 10/3/23 16:22, Jocelyn Falempe wrote:
> Add support for the drm_panic module, which displays a message to
> the screen when a kernel panic occurs.
>
> Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
> ---
> drivers/gpu/drm/mgag200/mgag200_drv.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c
> index 976f0ab2006b..229d9c116b42 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_drv.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
> @@ -12,10 +12,12 @@
> #include <drm/drm_aperture.h>
> #include <drm/drm_drv.h>
> #include <drm/drm_fbdev_generic.h>
> +#include <drm/drm_framebuffer.h>
> #include <drm/drm_file.h>
> #include <drm/drm_ioctl.h>
> #include <drm/drm_managed.h>
> #include <drm/drm_module.h>
> +#include <drm/drm_panic.h>
> #include <drm/drm_pciids.h>
>
> #include "mgag200_drv.h"
> @@ -83,6 +85,27 @@ resource_size_t mgag200_probe_vram(void __iomem *mem, resource_size_t size)
> return offset - 65536;
> }
>
> +static int mgag200_get_scanout_buffer(struct drm_device *dev,
> + struct drm_scanout_buffer *sb)
> +{
> + struct drm_plane *plane;
> + struct mga_device *mdev = to_mga_device(dev);
> + struct iosys_map map = IOSYS_MAP_INIT_VADDR_IOMEM(mdev->vram);
> +
> + /* mgag200 has only one plane */
> + drm_for_each_plane(plane, dev) {
In my first 2016 attempt on a panic handler I was told to trylock crtc
and plane and skip if it wasn't possible:
- We need locking. One of the biggest problems with the old oops handling
was that it was very good at trampling over driver state, causing more
(unrelated) oopses in kms code and making sure the original oops was no
longer visible. I think the shared code must take care of all the
locking needs to avoid fragile code in drivers. ww_mutex_trylock on the
drm_crtc and drm_plane should be enough (we need both for drivers where
planes can be reassigned between drivers).
See [1] for a list of other things to consider.
Noralf.
[1]
https://lore.kernel.org/dri-devel/20160810091529.GQ6232@phenom.ffwll.local/
> + if (!plane->state || !plane->state->fb)
> + return -ENODEV;
> + sb->format = plane->state->fb->format;
> + sb->width = plane->state->fb->width;
> + sb->height = plane->state->fb->height;
> + sb->pitch = plane->state->fb->pitches[0];
> + sb->map = map;
> + return 0;
> + }
> + return -ENODEV;
> +}
> +
> /*
> * DRM driver
> */
> @@ -98,6 +121,7 @@ static const struct drm_driver mgag200_driver = {
> .major = DRIVER_MAJOR,
> .minor = DRIVER_MINOR,
> .patchlevel = DRIVER_PATCHLEVEL,
> + .get_scanout_buffer = mgag200_get_scanout_buffer,
> DRM_GEM_SHMEM_DRIVER_OPS,
> };
>
