[RFC 5/8] drm/exynos: introduce BYTE_PITCH capability

[Tobias Jakobi]

In some of drivers we compute something like 'pitch / cpp' at some
point, silently assuming that the pitch (which is in bytes) is
divisible by the buffer's cpp. This is not always true, in particular
DRM core does not check for pitch alignment in the common case.

Introduce a new cap which signals that the hardware supports a
pitch with 'byte-granularity'. If the cap is not set, assume that
we need pitch aligned to cpp.

We set the cap later for the drivers/planes that support it.

Signed-off-by: Tobias Jakobi <tjakobi at math.uni-bielefeld.de>
---
 drivers/gpu/drm/exynos/exynos_drm_drv.h   |  1 +
 drivers/gpu/drm/exynos/exynos_drm_plane.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.h b/drivers/gpu/drm/exynos/exynos_drm_drv.h
index ee62b0b..8d957a9 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_drv.h
+++ b/drivers/gpu/drm/exynos/exynos_drm_drv.h
@@ -92,6 +92,7 @@ struct exynos_drm_plane {
 #define EXYNOS_DRM_PLANE_CAP_SCALE	(1 << 1)
 #define EXYNOS_DRM_PLANE_CAP_ZPOS	(1 << 2)
 #define EXYNOS_DRM_PLANE_CAP_TILE	(1 << 3)
+#define EXYNOS_DRM_PLANE_CAP_BYTE_PITCH	(1 << 4)
 
 /*
  * Exynos DRM plane configuration structure.
diff --git a/drivers/gpu/drm/exynos/exynos_drm_plane.c b/drivers/gpu/drm/exynos/exynos_drm_plane.c
index fa6333d..b31a226 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_plane.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_plane.c
@@ -185,6 +185,16 @@ exynos_drm_plane_check_format(const struct exynos_drm_plane_config *config,
 {
 	struct drm_framebuffer *fb = state->base.fb;
 
+	/*
+	 * Some blocks only allow to specify a buffer pitch in terms
+	 * of pixels. In these cases, we need to ensure that the pitch
+	 * provided by userspace is divisible by the cpp.
+	 */
+	if (!(config->capabilities & EXYNOS_DRM_PLANE_CAP_BYTE_PITCH)) {
+		if (fb->pitches[0] % fb->format->cpp[0])
+			return -ENOTSUPP;
+	}
+
 	switch (fb->modifier) {
 	case DRM_FORMAT_MOD_SAMSUNG_64_32_TILE:
 		if (!(config->capabilities & EXYNOS_DRM_PLANE_CAP_TILE))
-- 
2.7.3