[PATCH] drm/amdgpu: add dce6 drm_panic support

[Lu Yao]

Add support for the drm_panic module, which displays a pretty user
friendly message on the screen when a Linux kernel panic occurs.

Signed-off-by: Lu Yao <yaolu at kylinos.cn>
---
The patch can work properly on the TTY, but after start X, drawn
image is messy, it looks like the data isn't linearly arranged.
However at this time 'fb->modifier' is 'DRM_FORMAT_MOD_LINEAR'.

Another difference I found is:
  For TTY, the amdgpu_bo is created with flag
  'AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED|AMDGPU_GEM_CREATE_CPU_GTT_USWC|
  AMDGPU_GEM_CREATE_VRAM_CLEARED|AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS'.
  For X, the amdgpu_bo is created with flag
  'AMDGPU_GEM_CREATE_NO_CPU_ACCESS|AMDGPU_GEM_CREATE_CPU_GTT_USWC'
I try to use same flag for X, it looks like no difference.

Can someone provide some insight into this problem or where I am going
wrong. Thanks a lot.

Test environment: X86 arch + v6.6 kernel + R7340.
---
 drivers/gpu/drm/amd/amdgpu/dce_v6_0.c | 32 +++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/dce_v6_0.c b/drivers/gpu/drm/amd/amdgpu/dce_v6_0.c
index 05c0df97f01d..12c3801c264a 100644
--- a/drivers/gpu/drm/amd/amdgpu/dce_v6_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/dce_v6_0.c
@@ -28,6 +28,8 @@
 #include <drm/drm_modeset_helper.h>
 #include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_vblank.h>
+#include <drm/drm_panic.h>
+#include "../../drm_internal.h"
 
 #include "amdgpu.h"
 #include "amdgpu_pm.h"
@@ -2600,6 +2602,35 @@ static const struct drm_crtc_helper_funcs dce_v6_0_crtc_helper_funcs = {
 	.get_scanout_position = amdgpu_crtc_get_scanout_position,
 };
 
+static int dce_v6_0_drm_primary_plane_get_scanout_buffer(struct drm_plane *plane,
+							 struct drm_scanout_buffer *sb)
+{
+	struct drm_framebuffer *fb;
+	struct drm_gem_object *obj;
+	struct amdgpu_bo *abo;
+	int ret = 0;
+
+	if (!plane->fb || plane->fb->modifier != DRM_FORMAT_MOD_LINEAR)
+		return -ENODEV;
+
+	fb = plane->fb;
+	sb->width = fb->width;
+	sb->height = fb->height;
+	sb->format = fb->format;
+	sb->pitch[0] = fb->pitches[0];
+
+	obj = fb->obj[0];
+	abo = gem_to_amdgpu_bo(obj);
+	if (!abo || abo->flags & AMDGPU_GEM_CREATE_NO_CPU_ACCESS)
+		return -EINVAL;
+
+	return drm_gem_vmap(obj, &sb->map[0]);
+}
+
+static const struct drm_plane_helper_funcs dce_v6_0_drm_primary_plane_helper_funcs = {
+	.get_scanout_buffer = dce_v6_0_drm_primary_plane_get_scanout_buffer
+};
+
 static int dce_v6_0_crtc_init(struct amdgpu_device *adev, int index)
 {
 	struct amdgpu_crtc *amdgpu_crtc;
@@ -2627,6 +2658,7 @@ static int dce_v6_0_crtc_init(struct amdgpu_device *adev, int index)
 	amdgpu_crtc->encoder = NULL;
 	amdgpu_crtc->connector = NULL;
 	drm_crtc_helper_add(&amdgpu_crtc->base, &dce_v6_0_crtc_helper_funcs);
+	drm_plane_helper_add(amdgpu_crtc->base.primary, &dce_v6_0_drm_primary_plane_helper_funcs);
 
 	return 0;
 }
-- 
2.25.1