[PATCH v7 5/9] drm/fb_dma: Add generic get_scanout_buffer() for drm_panic

[Maxime Ripard]

Hi,

On Thu, Jan 04, 2024 at 05:00:49PM +0100, Jocelyn Falempe wrote:
> This was initialy done for imx6, but should work on most drivers
> using drm_fb_dma_helper.
> 
> Signed-off-by: Jocelyn Falempe <jfalempe at redhat.com>
> ---
>  drivers/gpu/drm/drm_fb_dma_helper.c | 55 +++++++++++++++++++++++++++++
>  include/drm/drm_fb_dma_helper.h     |  4 +++
>  2 files changed, 59 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_fb_dma_helper.c b/drivers/gpu/drm/drm_fb_dma_helper.c
> index 3b535ad1b07c..caed2935df4f 100644
> --- a/drivers/gpu/drm/drm_fb_dma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_dma_helper.c
> @@ -15,6 +15,7 @@
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_gem_dma_helper.h>
>  #include <drm/drm_gem_framebuffer_helper.h>
> +#include <drm/drm_panic.h>
>  #include <drm/drm_plane.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/module.h>
> @@ -148,3 +149,57 @@ void drm_fb_dma_sync_non_coherent(struct drm_device *drm,
>  	}
>  }
>  EXPORT_SYMBOL_GPL(drm_fb_dma_sync_non_coherent);
> +
> +#if defined(CONFIG_DRM_PANIC)
> +/**
> + * @dev: DRM device
> + * @drm_scanout_buffer: scanout buffer for the panic handler
> + * Returns: 0 or negative error code
> + *
> + * Generic get_scanout_buffer() implementation, for drivers that uses the
> + * drm_fb_dma_helper.
> + */
> +int drm_panic_gem_get_scanout_buffer(struct drm_device *dev,
> +				     struct drm_scanout_buffer *sb)
> +{
> +	struct drm_plane *plane;
> +	struct drm_gem_dma_object *dma_obj;
> +	struct drm_framebuffer *fb;
> +
> +	drm_for_each_primary_visible_plane(plane, dev) {
> +		fb = plane->state->fb;
> +		/* Only support linear modifier */
> +		if (fb->modifier != DRM_FORMAT_MOD_LINEAR)
> +			continue;
> +
> +		/* Check if color format is supported */
> +		if (!drm_panic_is_format_supported(fb->format->format))
> +			continue;
> +
> +		dma_obj = drm_fb_dma_get_gem_obj(fb, 0);
> +
> +		/* Buffer should be accessible from the CPU */
> +		if (dma_obj->base.import_attach)
> +			continue;
> +
> +		/* Buffer should be already mapped to CPU */
> +		if (!dma_obj->vaddr)
> +			continue;
> +
> +		iosys_map_set_vaddr(&sb->map, dma_obj->vaddr);
> +		sb->format = fb->format;
> +		sb->height = fb->height;
> +		sb->width = fb->width;
> +		sb->pitch = fb->pitches[0];
> +		return 0;
> +	}
> +	return -ENODEV;
> +}
> +#else
> +int drm_panic_gem_get_scanout_buffer(struct drm_device *dev,
> +				     struct drm_scanout_buffer *sb)
> +{
> +	return 0;
> +}
> +#endif
> +EXPORT_SYMBOL(drm_panic_gem_get_scanout_buffer);

Looks much better, thanks :)

I think we should be more vocal about the failure cases too. Maybe log
it through warn/pr_crit or whatever so that at least we have an idea
what went wrong in a post mortem.

Maxime
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