On Mon, Aug 18, 2014 at 10:11 AM Inki Dae inki.dae@samsung.com wrote:
This patch adds a new flag, MIPI_DSI-MODE_LPM, to transmit data in low power. With this flag, msg.flags has MIPI_DSI_MSG_USE_LPM so that host driver of each SoC can clear or set relevant register bit for low power transmission.
All host drivers shall support continuous clock behavior on the Clock Lane, and optionally may support non-continuous clock behavior. Both of them can transmit data in high speed of low power.
With each clock behavior, non-continuous or continuous clock mode, host controller will transmit data in high speed by default so if peripheral wants to receive data in low power, the peripheral driver should set MIPI_DSI_MODE_LPM flag.
Signed-off-by: Inki Dae inki.dae@samsung.com
Hi Inki Dae,
I recently used this flag in a driver to the effect that all writes become LPM, including updates to a command mode-only panel, so the pixels will draw very slowly on the screen. In this case I added the feature for debugging (my display works fine in LP but not yet in HS mode).
This is not a problem with a video mode panel since these are by the specification required to operate in HS mode, so we know they are always HS.
But in command mode, all commands are equal, even if they are screen updates. I program my hardware to update the display with a stream of commands, and with this flag set, that stream will go slow.
Is this how it is intended?
Using the flag like this is kind of interesting because it is good for debugging but I don't know if this is how it was intended.
If the flag is only supposed to be for DCS write commands, so that both write and read happen in LP mode, then we should probably rename it accordingly I think?
Yours, Linus Walleij