Am Wed, 2 Apr 2014 09:06:51 +0300 hat Tomi Valkeinen tomi.valkeinen@ti.com geschrieben:
Hi,
I've received some command examples for the chip and attached them.
Well, according to Solomon Systech, the display got a pin specifically for tear-free rotation when used with an OMAP5. Surely that pin has some reason... it wouldn't really make sense adding such pin if the OMAP5 can do the same with its own hardware. Something we really need to check.
I haven't really read the spec, but the chip looks like a normal DSI Command mode buffer chip, with some fancier features. The TE (tearing elimination or tearing effect) pin is a normal required pin on DSI Command mode devices, so there's nothing OMAP5 or OMAP specific with that.
Thanks for cleating that up.
With conventional displays the SoC will be driving the panel, i.e. the SoC will send vsync and hsync signals to the panel, and the panel will comply. With a buffer chip, the chip is driving the panel in the same way as SoC does with conventional panels. What this means is that (obviously) the SoC does _not_ drive the panel, which means that the SoC doesn't know when there vsync happens. TE is basically a vsync signal (although it can be programmed to give the signal at other points also). When the SoC gets the TE signal, it knows that it can start the frame transfer to the chip. This way tearing can be avoided, but only when rotation is not used.
Okay... so with rotation, we'll still have tearing? Hm. I'll send that question to the manufacturer.
So we have no way avoiding the tearing here with rotation?
I also need to point out that at the moment there's no automatic update support for DSI command mode displays in the omapdss driver. Normally the point of using DSI command mode displays is that you do not want to update the display from the SoC all the time. Instead, you only send new frame (or even just part of the frame) when something has changed. But automatic update is something that can be implemented in the driver.
Okay, if that's not too complex, then it's not a huge worry for me.