[PATCH v4] drm/mediatek: allow commands to be sent during video mode

[Julien STEPHAN <jstephan@xxxxxxxxxxxx>]

Mipi dsi panel drivers can use mipi_dsi_dcs_{set,get}_display_brightness()
to request backlight changes.

This can be done during panel initialization (dsi is in command mode)
or afterwards (dsi is in Video Mode).

When the DSI is in Video Mode, all commands are rejected.

Detect current DSI mode in mtk_dsi_host_transfer() and switch modes
temporarily to allow commands to be sent.

Signed-off-by: Julien STEPHAN <jstephan@xxxxxxxxxxxx>
Signed-off-by: Mattijs Korpershoek <mkorpershoek@xxxxxxxxxxxx>
---
Changes in v4:
    - fix missing space:  "ret : recv_cnt;"
Changes in v3:
    - increase readability of code and use correct return variable (see
      comment
https://lore.kernel.org/linux-mediatek/4907bdc1-b4a6-e9ad-5cfa-266fc20c0bec@xxxxxxxxxxxxx/)

Changes in v2:
    - update commit message to be more descriptive

 drivers/gpu/drm/mediatek/mtk_dsi.c | 33 ++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 5d90d2eb0019..abdd9cdebd86 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -891,24 +891,33 @@ static ssize_t mtk_dsi_host_transfer(struct mipi_dsi_host *host,
 	u8 read_data[16];
 	void *src_addr;
 	u8 irq_flag = CMD_DONE_INT_FLAG;
+	u32 dsi_mode;
+	int ret;

-	if (readl(dsi->regs + DSI_MODE_CTRL) & MODE) {
-		DRM_ERROR("dsi engine is not command mode\n");
-		return -EINVAL;
+	dsi_mode = readl(dsi->regs + DSI_MODE_CTRL);
+	if (dsi_mode & MODE) {
+		mtk_dsi_stop(dsi);
+		ret = mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
+		if (ret)
+			goto restore_dsi_mode;
 	}

 	if (MTK_DSI_HOST_IS_READ(msg->type))
 		irq_flag |= LPRX_RD_RDY_INT_FLAG;

-	if (mtk_dsi_host_send_cmd(dsi, msg, irq_flag) < 0)
-		return -ETIME;
+	ret = mtk_dsi_host_send_cmd(dsi, msg, irq_flag);
+	if (ret)
+		goto restore_dsi_mode;

-	if (!MTK_DSI_HOST_IS_READ(msg->type))
-		return 0;
+	if (!MTK_DSI_HOST_IS_READ(msg->type)) {
+		recv_cnt = 0;
+		goto restore_dsi_mode;
+	}

 	if (!msg->rx_buf) {
 		DRM_ERROR("dsi receive buffer size may be NULL\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto restore_dsi_mode;
 	}

 	for (i = 0; i < 16; i++)
@@ -933,7 +942,13 @@ static ssize_t mtk_dsi_host_transfer(struct mipi_dsi_host *host,
 	DRM_INFO("dsi get %d byte data from the panel address(0x%x)\n",
 		 recv_cnt, *((u8 *)(msg->tx_buf)));

-	return recv_cnt;
+restore_dsi_mode:
+	if (dsi_mode & MODE) {
+		mtk_dsi_set_mode(dsi);
+		mtk_dsi_start(dsi);
+	}
+
+	return ret < 0 ? ret : recv_cnt;
 }

 static const struct mipi_dsi_host_ops mtk_dsi_ops = {
--
2.35.1