drm/fourcc: Add char_per_block, block_w and block_h in drm_format_info

For some pixel formats .cpp structure in drm_format info it's not
enough to describe the peculiarities of the pixel layout, for example
tiled formats or packed formats at bit level.

What's implemented here is to add three new members to drm_format_info
that could describe such formats:

- char_per_block[3]
- block_w[3]
- block_h[3]

char_per_block will be put in a union alongside cpp, for transparent
compatibility with the existing format descriptions.

Regarding, block_w and block_h they are intended to be used through
their equivalent getters drm_format_info_block_width /
drm_format_info_block_height, the reason of the getters is to abstract
the fact that for normal formats block_w and block_h will be unset/0,
but the methods will be returning 1.

Additionally, convenience function drm_format_info_min_pitch had been
added that computes the minimum required pitch for a given pixel
format and buffer width.

Using that the following drm core functions had been updated to
generically handle both block and non-block formats:

- drm_fb_cma_get_gem_addr: for block formats it will just return the
beginning of the block.
- framebuffer_check: Use the newly added drm_format_info_min_pitch.
- drm_gem_fb_create_with_funcs: Use the newly added
drm_format_info_min_pitch.
- In places where is not expecting to handle block formats, like fbdev
helpers I just added some warnings in case the block width/height
are greater than 1.

Changes since v3:
- Add helper function for computing the minimum required pitch.
- Improve/cleanup documentation

Changes since v8:
- Fixed build on 32bits arm architectures, with:

- return DIV_ROUND_UP((u64)buffer_width * info->char_per_block[plane],
+ return DIV_ROUND_UP_ULL((u64)buffer_width * info->char_per_block[plane],

Reviewed-by: Brian Starkey <[e-mail]>
Reviewed-by: Daniel Vetter <[e-mail]>
Signed-off-by: Alexandru Gheorghe <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_fb_cma_helper.c

···
 EXPORT_SYMBOL_GPL(drm_fb_cma_get_gem_obj);
 
 /**
- * drm_fb_cma_get_gem_addr() - Get physical address for framebuffer
+ * drm_fb_cma_get_gem_addr() - Get physical address for framebuffer, for pixel
+ * formats where values are grouped in blocks this will get you the beginning of
+ * the block
  * @fb: The framebuffer
  * @state: Which state of drm plane
  * @plane: Which plane
···
 	struct drm_gem_cma_object *obj;
 	dma_addr_t paddr;
 	u8 h_div = 1, v_div = 1;
+	u32 block_w = drm_format_info_block_width(fb->format, plane);
+	u32 block_h = drm_format_info_block_height(fb->format, plane);
+	u32 block_size = fb->format->char_per_block[plane];
+	u32 sample_x;
+	u32 sample_y;
+	u32 block_start_y;
+	u32 num_hblocks;
 
 	obj = drm_fb_cma_get_gem_obj(fb, plane);
 	if (!obj)
···
 		v_div = fb->format->vsub;
 	}
 
-	paddr += (fb->format->cpp[plane] * (state->src_x >> 16)) / h_div;
-	paddr += (fb->pitches[plane] * (state->src_y >> 16)) / v_div;
+	sample_x = (state->src_x >> 16) / h_div;
+	sample_y = (state->src_y >> 16) / v_div;
+	block_start_y = (sample_y / block_h) * block_h;
+	num_hblocks = sample_x / block_w;
+
+	paddr += fb->pitches[plane] * block_start_y;
+	paddr += block_size * num_hblocks;
 
 	return paddr;
 }

drivers/gpu/drm/drm_fb_helper.c

···
 	if (var->pixclock != 0 || in_dbg_master())
 		return -EINVAL;
 
+	if ((drm_format_info_block_width(fb->format, 0) > 1) ||
+	    (drm_format_info_block_height(fb->format, 0) > 1))
+		return -EINVAL;
+
 	/*
 	 * Changes struct fb_var_screeninfo are currently not pushed back
 	 * to KMS, hence fail if different settings are requested.
···
 {
 	struct drm_framebuffer *fb = fb_helper->fb;
 
+	WARN_ON((drm_format_info_block_width(fb->format, 0) > 1) ||
+		(drm_format_info_block_height(fb->format, 0) > 1));
 	info->pseudo_palette = fb_helper->pseudo_palette;
 	info->var.xres_virtual = fb->width;
 	info->var.yres_virtual = fb->height;

drivers/gpu/drm/drm_fourcc.c

···
 	return height / info->vsub;
 }
 EXPORT_SYMBOL(drm_format_plane_height);
+
+/**
+ * drm_format_info_block_width - width in pixels of block.
+ * @info: pixel format info
+ * @plane: plane index
+ *
+ * Returns:
+ * The width in pixels of a block, depending on the plane index.
+ */
+unsigned int drm_format_info_block_width(const struct drm_format_info *info,
+					 int plane)
+{
+	if (!info || plane < 0 || plane >= info->num_planes)
+		return 0;
+
+	if (!info->block_w[plane])
+		return 1;
+	return info->block_w[plane];
+}
+EXPORT_SYMBOL(drm_format_info_block_width);
+
+/**
+ * drm_format_info_block_height - height in pixels of a block
+ * @info: pixel format info
+ * @plane: plane index
+ *
+ * Returns:
+ * The height in pixels of a block, depending on the plane index.
+ */
+unsigned int drm_format_info_block_height(const struct drm_format_info *info,
+					  int plane)
+{
+	if (!info || plane < 0 || plane >= info->num_planes)
+		return 0;
+
+	if (!info->block_h[plane])
+		return 1;
+	return info->block_h[plane];
+}
+EXPORT_SYMBOL(drm_format_info_block_height);
+
+/**
+ * drm_format_info_min_pitch - computes the minimum required pitch in bytes
+ * @info: pixel format info
+ * @plane: plane index
+ * @buffer_width: buffer width in pixels
+ *
+ * Returns:
+ * The minimum required pitch in bytes for a buffer by taking into consideration
+ * the pixel format information and the buffer width.
+ */
+uint64_t drm_format_info_min_pitch(const struct drm_format_info *info,
+				   int plane, unsigned int buffer_width)
+{
+	if (!info || plane < 0 || plane >= info->num_planes)
+		return 0;
+
+	return DIV_ROUND_UP_ULL((u64)buffer_width * info->char_per_block[plane],
+			    drm_format_info_block_width(info, plane) *
+			    drm_format_info_block_height(info, plane));
+}
+EXPORT_SYMBOL(drm_format_info_min_pitch);

drivers/gpu/drm/drm_framebuffer.c

···
 	for (i = 0; i < info->num_planes; i++) {
 		unsigned int width = fb_plane_width(r->width, info, i);
 		unsigned int height = fb_plane_height(r->height, info, i);
-		unsigned int cpp = info->cpp[i];
+		u64 min_pitch = drm_format_info_min_pitch(info, i, width);
 
 		if (!r->handles[i]) {
 			DRM_DEBUG_KMS("no buffer object handle for plane %d\n", i);
 			return -EINVAL;
 		}
 
-		if ((uint64_t) width * cpp > UINT_MAX)
+		if (min_pitch > UINT_MAX)
 			return -ERANGE;
 
 		if ((uint64_t) height * r->pitches[i] + r->offsets[i] > UINT_MAX)
 			return -ERANGE;
 
-		if (r->pitches[i] < width * cpp) {
+		if (r->pitches[i] < min_pitch) {
 			DRM_DEBUG_KMS("bad pitch %u for plane %d\n", r->pitches[i], i);
 			return -EINVAL;
 		}

drivers/gpu/drm/drm_gem_framebuffer_helper.c

···
 		}
 
 		min_size = (height - 1) * mode_cmd->pitches[i]
-			 + width * info->cpp[i]
+			 + drm_format_info_min_pitch(info, i, width)
 			 + mode_cmd->offsets[i];
 
 		if (objs[i]->size < min_size) {

include/drm/drm_fourcc.h

···
 	/** @num_planes: Number of color planes (1 to 3) */
 	u8 num_planes;
 
-	/** @cpp: Number of bytes per pixel (per plane) */
-	u8 cpp[3];
+	union {
+		/**
+		 * @cpp:
+		 *
+		 * Number of bytes per pixel (per plane), this is aliased with
+		 * @char_per_block. It is deprecated in favour of using the
+		 * triplet @char_per_block, @block_w, @block_h for better
+		 * describing the pixel format.
+		 */
+		u8 cpp[3];
+
+		/**
+		 * @char_per_block:
+		 *
+		 * Number of bytes per block (per plane), where blocks are
+		 * defined as a rectangle of pixels which are stored next to
+		 * each other in a byte aligned memory region. Together with
+		 * @block_w and @block_h this is used to properly describe tiles
+		 * in tiled formats or to describe groups of pixels in packed
+		 * formats for which the memory needed for a single pixel is not
+		 * byte aligned.
+		 *
+		 * @cpp has been kept for historical reasons because there are
+		 * a lot of places in drivers where it's used. In drm core for
+		 * generic code paths the preferred way is to use
+		 * @char_per_block, drm_format_info_block_width() and
+		 * drm_format_info_block_height() which allows handling both
+		 * block and non-block formats in the same way.
+		 *
+		 * For formats that are intended to be used only with non-linear
+		 * modifiers both @cpp and @char_per_block must be 0 in the
+		 * generic format table. Drivers could supply accurate
+		 * information from their drm_mode_config.get_format_info hook
+		 * if they want the core to be validating the pitch.
+		 */
+		u8 char_per_block[3];
+	};
+
+	/**
+	 * @block_w:
+	 *
+	 * Block width in pixels, this is intended to be accessed through
+	 * drm_format_info_block_width()
+	 */
+	u8 block_w[3];
+
+	/**
+	 * @block_h:
+	 *
+	 * Block height in pixels, this is intended to be accessed through
+	 * drm_format_info_block_height()
+	 */
+	u8 block_h[3];
 
 	/** @hsub: Horizontal chroma subsampling factor */
 	u8 hsub;
···
 int drm_format_vert_chroma_subsampling(uint32_t format);
 int drm_format_plane_width(int width, uint32_t format, int plane);
 int drm_format_plane_height(int height, uint32_t format, int plane);
+unsigned int drm_format_info_block_width(const struct drm_format_info *info,
+					 int plane);
+unsigned int drm_format_info_block_height(const struct drm_format_info *info,
+					  int plane);
+uint64_t drm_format_info_min_pitch(const struct drm_format_info *info,
+				   int plane, unsigned int buffer_width);
 const char *drm_get_format_name(uint32_t format, struct drm_format_name_buf *buf);
 
 #endif /* __DRM_FOURCC_H__ */