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

[Jocelyn Falempe]

On 08/01/2024 11:20, Maxime Ripard wrote:

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 <jfale...@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.

Thanks for the review.
Yes I can add an error message when it fails to find a scanout buffer.

Maxime

--

Jocelyn