[PATCH v3 3/5] drm/exynos: fbdev: Calculate buffer geometry with format helpers

[Thomas Zimmermann <tzimmermann@suse.de>]

Replace the geometry and size calculation in exynos' fbdev emulation
with DRM format helpers. This consists of a 4CC lookup from the fbdev
parameters, format lookup, pitch calculation and size calculation.

Then allocate the GEM buffer object for the framebuffer memory from
the calculated size. Mmap provides the allocated buffer to user space,
so align the buffer size to PAGE_SIZE.

Initialize the fields screen_size and fix.smem_len in struct fb_info
from the size of the allocated buffer object. This is the real size
and can differ from the requested size.

v3:
- add more error checks to geometry calculations

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/gpu/drm/exynos/exynos_drm_fbdev.c | 45 +++++++++++++++--------
 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
index 1c564edd497e..9163efd676dd 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
@@ -60,11 +60,14 @@ static const struct drm_fb_helper_funcs exynos_drm_fbdev_helper_funcs = {
 int exynos_drm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
 					struct drm_fb_helper_surface_size *sizes)
 {
-	struct exynos_drm_gem *exynos_gem;
 	struct drm_device *dev = helper->dev;
 	struct fb_info *info = helper->info;
+	u32 fourcc, pitch;
+	u64 size;
+	const struct drm_format_info *format;
+	struct exynos_drm_gem *exynos_gem;
+	struct drm_gem_object *obj;
 	struct drm_mode_fb_cmd2 mode_cmd = { 0 };
-	unsigned long size;
 	int ret;
 
 	DRM_DEV_DEBUG_KMS(dev->dev,
@@ -72,23 +75,33 @@ int exynos_drm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
 			  sizes->surface_width, sizes->surface_height,
 			  sizes->surface_bpp);
 
-	mode_cmd.width = sizes->surface_width;
-	mode_cmd.height = sizes->surface_height;
-	mode_cmd.pitches[0] = sizes->surface_width * (sizes->surface_bpp >> 3);
-	mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
-							  sizes->surface_depth);
-
-	size = mode_cmd.pitches[0] * mode_cmd.height;
+	fourcc = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
+	if (fourcc == DRM_FORMAT_INVALID)
+		return -EINVAL;
+	format = drm_get_format_info(dev, fourcc, DRM_FORMAT_MOD_LINEAR);
+	if (!format)
+		return -EINVAL;
+	pitch = drm_format_info_min_pitch(format, 0, sizes->surface_width);
+	if (!pitch)
+		return -EINVAL;
+	if (check_mul_overflow(pitch, sizes->surface_height, &size))
+		return -EINVAL;
+	size = ALIGN(size, PAGE_SIZE);
+	if (size < PAGE_SIZE)
+		return -EINVAL;
 
 	exynos_gem = exynos_drm_gem_create(dev, EXYNOS_BO_WC, size, true);
 	if (IS_ERR(exynos_gem))
 		return PTR_ERR(exynos_gem);
+	obj = &exynos_gem->base;
+
+	mode_cmd.width = sizes->surface_width;
+	mode_cmd.height = sizes->surface_height;
+	mode_cmd.pixel_format = fourcc;
+	mode_cmd.pitches[0] = pitch;
+	mode_cmd.modifier[0] = DRM_FORMAT_MOD_LINEAR;
 
-	helper->fb =
-		exynos_drm_framebuffer_init(dev,
-					    drm_get_format_info(dev, mode_cmd.pixel_format,
-								mode_cmd.modifier[0]),
-					    &mode_cmd, &exynos_gem, 1);
+	helper->fb = exynos_drm_framebuffer_init(dev, format, &mode_cmd, &exynos_gem, 1);
 	if (IS_ERR(helper->fb)) {
 		DRM_DEV_ERROR(dev->dev, "failed to create drm framebuffer.\n");
 		ret = PTR_ERR(helper->fb);
@@ -102,8 +115,8 @@ int exynos_drm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
 
 	info->flags |= FBINFO_VIRTFB;
 	info->screen_buffer = exynos_gem->kvaddr;
-	info->screen_size = size;
-	info->fix.smem_len = size;
+	info->screen_size = obj->size;
+	info->fix.smem_len = obj->size;
 
 	return 0;
 
-- 
2.54.0