[PATCH 13/15] drm/dsi: Always use low-power mode for DCS commands

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

Many peripherals require DCS commands to be sent in low power mode and
will fail to correctly process them in high speed mode. Section 5.2 of
the MIPI DSI specification also mandates that on bidirectional lanes,
data shall be transmitted in low power mode only. At worst this change
will make transmission of DCS commands slower than optimal on some DSI
peripherals, but it should enable DCS commands to be successfully
transmitted to any DSI peripheral.

If transmission in low power mode turns out to be too slow at some point
in the future, one possible solution would be to explicitly mark devices
that support high speed transmission of DCS commands.

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/drm/drm_mipi_dsi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index d4d3cf752be7..a0b9c7ea77a7 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -370,6 +370,7 @@ ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
 {
 	struct mipi_dsi_msg msg = {
 		.channel = dsi->channel,
+		.flags = MIPI_DSI_MSG_USE_LPM,
 		.tx_buf = data,
 		.tx_len = len
 	};
@@ -457,6 +458,7 @@ ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
 	}
 
 	memset(&msg, 0, sizeof(msg));
+	msg.flags = MIPI_DSI_MSG_USE_LPM;
 	msg.channel = dsi->channel;
 	msg.tx_len = size;
 	msg.tx_buf = tx;
@@ -500,6 +502,7 @@ ssize_t mipi_dsi_dcs_read(struct mipi_dsi_device *dsi, u8 cmd, void *data,
 	struct mipi_dsi_msg msg = {
 		.channel = dsi->channel,
 		.type = MIPI_DSI_DCS_READ,
+		.flags = MIPI_DSI_MSG_USE_LPM,
 		.tx_buf = &cmd,
 		.tx_len = 1,
 		.rx_buf = data,
-- 
2.1.2