drm/simpledrm: Support virtual screen sizes

Add constants for the maximum size of the shadow-plane surface
size. Useful for shadow planes with virtual screen sizes. The
current sizes are 4096 scanlines with 4096 pixels each. This
seems reasonable for current hardware, but can be increased as
necessary.

In simpledrm, set the maximum framebuffer size from the constants
for shadow planes. Implements support for virtual screen sizes and
page flipping on the fbdev console.

v3:
	* use decimal numbers for shadow-plane constants (Noralf)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211110103702.374-9-tzimmermann@suse.de

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index 7c7d0aca8e31e4e09ed849142371481dab1ebd0c..2f999915b9aad0c4097ee69deffb78d9ced84404 100644 (file)
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -2,6 +2,7 @@
 
 #include <linux/clk.h>
 #include <linux/of_clk.h>
+#include <linux/minmax.h>
 #include <linux/platform_data/simplefb.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
@@ -772,6 +773,7 @@ static int simpledrm_device_init_modeset(struct simpledrm_device *sdev)
        struct drm_display_mode *mode = &sdev->mode;
        struct drm_connector *connector = &sdev->connector;
        struct drm_simple_display_pipe *pipe = &sdev->pipe;
+       unsigned long max_width, max_height;
        const uint32_t *formats;
        size_t nformats;
        int ret;
@@ -780,10 +782,13 @@ static int simpledrm_device_init_modeset(struct simpledrm_device *sdev)
        if (ret)
                return ret;
 
+       max_width = max_t(unsigned long, mode->hdisplay, DRM_SHADOW_PLANE_MAX_WIDTH);
+       max_height = max_t(unsigned long, mode->vdisplay, DRM_SHADOW_PLANE_MAX_HEIGHT);
+
        dev->mode_config.min_width = mode->hdisplay;
-       dev->mode_config.max_width = mode->hdisplay;
+       dev->mode_config.max_width = max_width;
        dev->mode_config.min_height = mode->vdisplay;
-       dev->mode_config.max_height = mode->vdisplay;
+       dev->mode_config.max_height = max_height;
        dev->mode_config.prefer_shadow_fbdev = true;
        dev->mode_config.preferred_depth = sdev->format->cpp[0] * 8;
        dev->mode_config.funcs = &simpledrm_mode_config_funcs;

diff --git a/include/drm/drm_gem_atomic_helper.h b/include/drm/drm_gem_atomic_helper.h
index 48222a107873725fbd84c785aeed057d38259429..0b1e2dd2ac3ffd92decc9fe540f62a23dfaa27ee 100644 (file)
--- a/include/drm/drm_gem_atomic_helper.h
+++ b/include/drm/drm_gem_atomic_helper.h
@@ -22,6 +22,24 @@ int drm_gem_simple_display_pipe_prepare_fb(struct drm_simple_display_pipe *pipe,
  * Helpers for planes with shadow buffers
  */
 
+/**
+ * DRM_SHADOW_PLANE_MAX_WIDTH - Maximum width of a plane's shadow buffer in pixels
+ *
+ * For drivers with shadow planes, the maximum width of the framebuffer is
+ * usually independent from hardware limitations. Drivers can initialize struct
+ * drm_mode_config.max_width from DRM_SHADOW_PLANE_MAX_WIDTH.
+ */
+#define DRM_SHADOW_PLANE_MAX_WIDTH     (4096u)
+
+/**
+ * DRM_SHADOW_PLANE_MAX_HEIGHT - Maximum height of a plane's shadow buffer in scanlines
+ *
+ * For drivers with shadow planes, the maximum height of the framebuffer is
+ * usually independent from hardware limitations. Drivers can initialize struct
+ * drm_mode_config.max_height from DRM_SHADOW_PLANE_MAX_HEIGHT.
+ */
+#define DRM_SHADOW_PLANE_MAX_HEIGHT    (4096u)
+
 /**
  * struct drm_shadow_plane_state - plane state for planes with shadow buffers
  *