media: allegro: add encoder buffer support

The encoder buffer serves as a cache for reference frames during the
encoding process. The encoder buffer significantly reduces the bandwidth
requirement for read accesses on the AXI ports of the VCU, but slightly
reduces the quality of the encoded video.

The encoder buffer must be configured as a whole during the firmware
initialization and later explicitly enabled for every channel that shall
use the encoder buffer.

Prior to firmware version 2019.2, it was necessary to explicitly set the
size of the encoder buffer for every channel. Since 2019.2 it is
sufficient to enable the encoder buffer and leave the rest to the
firmware. Therefore, only support the encoder buffer for firmware 2019.2
and later.

Signed-off-by: Michael Tretter <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/platform/allegro-dvt/allegro-core.c

···
 	struct mutex lock;
 };
 
+struct allegro_encoder_buffer {
+	unsigned int size;
+	unsigned int color_depth;
+	unsigned int num_cores;
+	unsigned int clk_rate;
+};
+
 struct allegro_dev {
 	struct v4l2_device v4l2_dev;
 	struct video_device video_dev;
···
 	const struct fw_info *fw_info;
 	struct allegro_buffer firmware;
 	struct allegro_buffer suballocator;
+	bool has_encoder_buffer;
+	struct allegro_encoder_buffer encoder_buffer;
 
 	struct completion init_complete;
 	bool initialized;
···
 	kfree(msg);
 }
 
+static int allegro_encoder_buffer_init(struct allegro_dev *dev,
+				       struct allegro_encoder_buffer *buffer)
+{
+	int err;
+	struct regmap *settings = dev->settings;
+	unsigned int supports_10_bit;
+	unsigned int memory_depth;
+	unsigned int num_cores;
+	unsigned int color_depth;
+	unsigned long clk_rate;
+
+	/* We don't support the encoder buffer pre Firmware version 2019.2 */
+	if (dev->fw_info->mailbox_version < MCU_MSG_VERSION_2019_2)
+		return -ENODEV;
+
+	if (!settings)
+		return -EINVAL;
+
+	err = regmap_read(settings, VCU_ENC_COLOR_DEPTH, &supports_10_bit);
+	if (err < 0)
+		return err;
+	err = regmap_read(settings, VCU_MEMORY_DEPTH, &memory_depth);
+	if (err < 0)
+		return err;
+	err = regmap_read(settings, VCU_NUM_CORE, &num_cores);
+	if (err < 0)
+		return err;
+
+	clk_rate = clk_get_rate(dev->clk_core);
+	if (clk_rate == 0)
+		return -EINVAL;
+
+	color_depth = supports_10_bit ? 10 : 8;
+	/* The firmware expects the encoder buffer size in bits. */
+	buffer->size = color_depth * 32 * memory_depth;
+	buffer->color_depth = color_depth;
+	buffer->num_cores = num_cores;
+	buffer->clk_rate = clk_rate;
+
+	v4l2_dbg(1, debug, &dev->v4l2_dev,
+		 "using %d bits encoder buffer with %d-bit color depth\n",
+		 buffer->size, color_depth);
+
+	return 0;
+}
+
 static void allegro_mcu_send_init(struct allegro_dev *dev,
 				  dma_addr_t suballoc_dma, size_t suballoc_size)
 {
···
 	msg.suballoc_dma = to_mcu_addr(dev, suballoc_dma);
 	msg.suballoc_size = to_mcu_size(dev, suballoc_size);
 
-	/* disable L2 cache */
-	msg.l2_cache[0] = -1;
-	msg.l2_cache[1] = -1;
-	msg.l2_cache[2] = -1;
+	if (dev->has_encoder_buffer) {
+		msg.encoder_buffer_size = dev->encoder_buffer.size;
+		msg.encoder_buffer_color_depth = dev->encoder_buffer.color_depth;
+		msg.num_cores = dev->encoder_buffer.num_cores;
+		msg.clk_rate = dev->encoder_buffer.clk_rate;
+	} else {
+		msg.encoder_buffer_size = -1;
+		msg.encoder_buffer_color_depth = -1;
+		msg.num_cores = -1;
+		msg.clk_rate = -1;
+	}
 
 	allegro_mbox_send(dev->mbox_command, &msg);
 }
···
 	param->max_transfo_depth_intra = channel->max_transfo_depth_intra;
 	param->max_transfo_depth_inter = channel->max_transfo_depth_inter;
 
-	param->prefetch_auto = 0;
-	param->prefetch_mem_offset = 0;
-	param->prefetch_mem_size = 0;
+	param->encoder_buffer_enabled = channel->dev->has_encoder_buffer;
+	param->encoder_buffer_offset = 0;
 
 	param->rate_control_mode = channel->frame_rc_enable ?
 		v4l2_bitrate_mode_to_mcu_mode(bitrate_mode) : 0;
···
 					 u64 src_handle)
 {
 	struct mcu_msg_encode_frame msg;
+	bool use_encoder_buffer = channel->dev->has_encoder_buffer;
 
 	memset(&msg, 0, sizeof(msg));
 
···
 
 	msg.channel_id = channel->mcu_channel_id;
 	msg.encoding_options = AL_OPT_FORCE_LOAD;
+	if (use_encoder_buffer)
+		msg.encoding_options |= AL_OPT_USE_L2;
 	msg.pps_qp = 26; /* qp are relative to 26 */
 	msg.user_param = 0; /* copied to mcu_msg_encode_frame_response */
 	/* src_handle is copied to mcu_msg_encode_frame_response */
···
 			 "failed to initialize mailboxes\n");
 		return -EIO;
 	}
+
+	err = allegro_encoder_buffer_init(dev, &dev->encoder_buffer);
+	dev->has_encoder_buffer = (err == 0);
+	if (!dev->has_encoder_buffer)
+		v4l2_info(&dev->v4l2_dev, "encoder buffer not available\n");
 
 	allegro_mcu_enable_interrupts(dev);
 

drivers/media/platform/allegro-dvt/allegro-mail.c

···
 	dst[i++] = msg->reserved0;
 	dst[i++] = msg->suballoc_dma;
 	dst[i++] = msg->suballoc_size;
-	dst[i++] = msg->l2_cache[0];
-	dst[i++] = msg->l2_cache[1];
-	dst[i++] = msg->l2_cache[2];
+	dst[i++] = msg->encoder_buffer_size;
+	dst[i++] = msg->encoder_buffer_color_depth;
+	dst[i++] = msg->num_cores;
 	if (version >= MCU_MSG_VERSION_2019_2) {
-		dst[i++] = -1;
+		dst[i++] = msg->clk_rate;
 		dst[i++] = 0;
 	}
 
···
 		   FIELD_PREP(GENMASK(7, 0), param->tc_offset);
 	dst[i++] = param->unknown11;
 	dst[i++] = param->unknown12;
-	if (version >= MCU_MSG_VERSION_2019_2)
-		dst[i++] = param->num_slices;
-	else
-		dst[i++] = FIELD_PREP(GENMASK(31, 16), param->prefetch_auto) |
-			   FIELD_PREP(GENMASK(15, 0), param->num_slices);
-	dst[i++] = param->prefetch_mem_offset;
-	dst[i++] = param->prefetch_mem_size;
+	dst[i++] = param->num_slices;
+	dst[i++] = param->encoder_buffer_offset;
+	dst[i++] = param->encoder_buffer_enabled;
+
 	dst[i++] = FIELD_PREP(GENMASK(31, 16), param->clip_vrt_range) |
 		   FIELD_PREP(GENMASK(15, 0), param->clip_hrz_range);
 	dst[i++] = FIELD_PREP(GENMASK(31, 16), param->me_range[1]) |

drivers/media/platform/allegro-dvt/allegro-mail.h

···
 	u32 reserved0;		/* maybe a unused channel id */
 	u32 suballoc_dma;
 	u32 suballoc_size;
-	s32 l2_cache[3];
+	s32 encoder_buffer_size;
+	s32 encoder_buffer_color_depth;
+	s32 num_cores;
+	s32 clk_rate;
 };
 
 struct mcu_msg_init_response {
···
 	u32 unknown11;
 	u32 unknown12;
 	u16 num_slices;
-	u16 prefetch_auto;
-	u32 prefetch_mem_offset;
-	u32 prefetch_mem_size;
+	u32 encoder_buffer_offset;
+	u32 encoder_buffer_enabled;
 	u16 clip_hrz_range;
 	u16 clip_vrt_range;
 	u16 me_range[4];