Am 01.04.2014 um 15:22 schrieb Dr. H. Nikolaus Schaller:
Am 01.04.2014 um 15:11 schrieb Tomi Valkeinen:
On 29/03/14 22:23, Michael Mrozek wrote:
Hi,
as we don't know yet if our current display will ever be working with proper speed rotating it with TILER, I've searched for some solutions.
Solomon Systech offers a MIPI bridge chip that can do stuff like rotation, scaling, color corrections, power saving, etc. That would be rotating without using the main system, so without any loss.
I've contacted them (find the datasheet of the chip attached). The chip has a pin connection for the OMAP5 for tear-free rotation.
The downside is: That chip can only do rotation up to 720x1280, so our display would not work.
If you use chip like that, make sure the rotation actually works. I don't know if they have something magical there, but normally you need a double buffer fb in the chip to support rotation. One buffer is written by the SoC, while the other is sent to the LCD. If there's just a single buffer, you'll get diagonal tearing.
Thanks for the hint!
I have looked into the data sheet and it appears that even 720x1280 drives the chip to its limits:
• Half-WUXGA (0.5 x 1920 x 1200 pixels) frame buffer • Support rotation up to 1280x800 resolution with SSL Compression • Support rotation up to 960x600 resolution without image compression
So it has only enough on-chip RAM for a single buffer.
And SSL-Compression means:
"SSL segment-based (4 pixels per segment) data compression/decompression with zero software overhead"
So it appears that we won't get full resolution 720x1280 rotated with that chip with less problems than with OMAP5 TILER! The problems will just be somewhere else.
And one more thing to consider:
110 mA @ 1.2V = 130 mW.
This means (assuming 90% efficiency) 40 mA @ 3.7V additional battery drain (in addition to the panel).
Well, this is difficult to compare to the additional energy consumption of the OMAP5 and TILER.
BR, Nikolaus