drm/dsi: Add message to packet translator

This commit introduces a new function, mipi_dsi_create_packet(), which
converts from a MIPI DSI message to a MIPI DSI packet. The MIPI DSI
packet is as close to the protocol described in the DSI specification as
possible and useful in drivers that need to write a DSI packet into a
FIFO to send a message off to the peripheral.

Suggested-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index adf056677498..44ff665f216f 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -266,6 +266,59 @@ bool mipi_dsi_packet_format_is_long(u8 type)
 EXPORT_SYMBOL(mipi_dsi_packet_format_is_long);
 
 /**
+ * mipi_dsi_create_packet - create a packet from a message according to the
+ *     DSI protocol
+ * @packet: pointer to a DSI packet structure
+ * @msg: message to translate into a packet
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_create_packet(struct mipi_dsi_packet *packet,
+                           const struct mipi_dsi_msg *msg)
+{
+        const u8 *tx = msg->tx_buf;
+
+        if (!packet || !msg)
+                return -EINVAL;
+
+        /* do some minimum sanity checking */
+        if (!mipi_dsi_packet_format_is_short(msg->type) &&
+            !mipi_dsi_packet_format_is_long(msg->type))
+                return -EINVAL;
+
+        if (msg->channel > 3)
+                return -EINVAL;
+
+        memset(packet, 0, sizeof(*packet));
+        packet->header[0] = ((msg->channel & 0x3) << 6) | (msg->type & 0x3f);
+
+        /* TODO: compute ECC if hardware support is not available */
+
+        /*
+         * Long write packets contain the word count in header bytes 1 and 2.
+         * The payload follows the header and is word count bytes long.
+         *
+         * Short write packets encode up to two parameters in header bytes 1
+         * and 2.
+         */
+        if (mipi_dsi_packet_format_is_long(msg->type)) {
+                packet->header[1] = (msg->tx_len >> 0) & 0xff;
+                packet->header[2] = (msg->tx_len >> 8) & 0xff;
+
+                packet->payload_length = msg->tx_len;
+                packet->payload = tx;
+        } else {
+                packet->header[1] = (msg->tx_len > 0) ? tx[0] : 0;
+                packet->header[2] = (msg->tx_len > 1) ? tx[1] : 0;
+        }
+
+        packet->size = sizeof(packet->header) + packet->payload_length;
+
+        return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_create_packet);
+
+/**
  * mipi_dsi_dcs_write - send DCS write command
  * @dsi: DSI device
  * @data: pointer to the command followed by parameters