drm/dsi: add helpers for DSI compression mode and PPS packets

Add helper functions for sending the DSI compression mode and picture
parameter set data type packets. For the time being, limit the support
to using VESA DSC 1.1 and the default PPS. This may need updating if the
need arises for proprietary compression or non-default PPS, however keep
it simple for starters.

v2: Add missing EXPORT_SYMBOL

Cc: Vandita Kulkarni <[e-mail]>
Reviewed-by: Thierry Reding <[e-mail]>
Signed-off-by: Jani Nikula <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_mipi_dsi.c

···
 #include <linux/pm_runtime.h>
 #include <linux/slab.h>
 
+#include <drm/drm_dsc.h>
 #include <video/mipi_display.h>
 
 /**
···
 	return (ret < 0) ? ret : 0;
 }
 EXPORT_SYMBOL(mipi_dsi_set_maximum_return_packet_size);
+
+/**
+ * mipi_dsi_compression_mode() - enable/disable DSC on the peripheral
+ * @dsi: DSI peripheral device
+ * @enable: Whether to enable or disable the DSC
+ *
+ * Enable or disable Display Stream Compression on the peripheral using the
+ * default Picture Parameter Set and VESA DSC 1.1 algorithm.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+ssize_t mipi_dsi_compression_mode(struct mipi_dsi_device *dsi, bool enable)
+{
+	/* Note: Needs updating for non-default PPS or algorithm */
+	u8 tx[2] = { enable << 0, 0 };
+	struct mipi_dsi_msg msg = {
+		.channel = dsi->channel,
+		.type = MIPI_DSI_COMPRESSION_MODE,
+		.tx_len = sizeof(tx),
+		.tx_buf = tx,
+	};
+	int ret = mipi_dsi_device_transfer(dsi, &msg);
+
+	return (ret < 0) ? ret : 0;
+}
+EXPORT_SYMBOL(mipi_dsi_compression_mode);
+
+/**
+ * mipi_dsi_picture_parameter_set() - transmit the DSC PPS to the peripheral
+ * @dsi: DSI peripheral device
+ * @pps: VESA DSC 1.1 Picture Parameter Set
+ *
+ * Transmit the VESA DSC 1.1 Picture Parameter Set to the peripheral.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+ssize_t mipi_dsi_picture_parameter_set(struct mipi_dsi_device *dsi,
+				       const struct drm_dsc_picture_parameter_set *pps)
+{
+	struct mipi_dsi_msg msg = {
+		.channel = dsi->channel,
+		.type = MIPI_DSI_PICTURE_PARAMETER_SET,
+		.tx_len = sizeof(*pps),
+		.tx_buf = pps,
+	};
+	int ret = mipi_dsi_device_transfer(dsi, &msg);
+
+	return (ret < 0) ? ret : 0;
+}
+EXPORT_SYMBOL(mipi_dsi_picture_parameter_set);
 
 /**
  * mipi_dsi_generic_write() - transmit data using a generic write packet

include/drm/drm_mipi_dsi.h

···
 
 struct mipi_dsi_host;
 struct mipi_dsi_device;
+struct drm_dsc_picture_parameter_set;
 
 /* request ACK from peripheral */
 #define MIPI_DSI_MSG_REQ_ACK	BIT(0)
···
 int mipi_dsi_turn_on_peripheral(struct mipi_dsi_device *dsi);
 int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,
 					    u16 value);
+ssize_t mipi_dsi_compression_mode(struct mipi_dsi_device *dsi, bool enable);
+ssize_t mipi_dsi_picture_parameter_set(struct mipi_dsi_device *dsi,
+				       const struct drm_dsc_picture_parameter_set *pps);
 
 ssize_t mipi_dsi_generic_write(struct mipi_dsi_device *dsi, const void *payload,
 			       size_t size);