On 10/13/2014 12:16 PM, Thierry Reding wrote:
From: Thierry Reding treding@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.
I guess you are referring to phrase: "For bidirectional Lanes, data shall be transmitted in the peripheral-to-processor, or reverse, direction using Low-Power (LP) Mode only".
This phrase is not clear but I guess the part "peripheral-to-processor, or reverse, direction" should be read as "peripheral-to-processor (ie. reverse) direction". Otherwise we would end up with insane restriction.
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.
I can imagine necessity of sending DCS/MCS commands in blank periods of video mode. In such case speed matters and in corner cases it will not be even possible to transmit message in LP mode.
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.
We have MIPI_DSI_MODE_LPM flag in dsi.mode_flags it should be enough, DCS helper should just check it.
Regards Andrzej
Signed-off-by: Thierry Reding treding@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,@@ -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,