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authorManjunathappa, Prakash <prakash.pm@ti.com>2012-07-18 21:01:56 +0530
committerFlorian Tobias Schandinat <FlorianSchandinat@gmx.de>2012-07-29 01:09:27 +0000
commitdeb95c6c958f5ba97b6b89ab18917bf79cb8ce7b (patch)
treebfaa9d4baaee6cf4232be798bfe88095c74acc50 /include/video
parent8a81dccd391a3e78f502da137de8fb62020c5809 (diff)
downloadop-kernel-dev-deb95c6c958f5ba97b6b89ab18917bf79cb8ce7b.zip
op-kernel-dev-deb95c6c958f5ba97b6b89ab18917bf79cb8ce7b.tar.gz
video: da8xx-fb: fix flicker due to 1 frame delay in updated frame
Flicker/tearing effect is observed with current FB driver. Issue is because of 2 active DMA channels ping ponging among them along with usage of 2 DDR ping pong buffers in driver. Application unaware of active DMA channel keeps updating frame being displayed, this leads to tearing effect. Below steps describes the issue: 1)Initially assume both buffers FB0 and FB1 are programmed for buffer-0. 2)On EOF0: Program FB0 for buffer-1, indicate(wake up) application to fill up buffer-0. As FB1 is active and continues to DMA buffer-0 (which is being filled), leading to tearing/flickering issue. 3)On EOF1: Program FB1 for buffer-0, indicate(wake up) application to fill up buffer-1. As FB0 is active and continues to DMA buffer-1(which is being filled), leading to tearing/flickering issue. 4)On EOF0: Program FB0 for buffer-1, indicate(wake up) application to fill up buffer-0. As FB1 is active and continues to DMA buffer-0(which is being filled), leading to tearing/flickering issue. ... Above steps depict that issue is because of 1 frame delay in frame panned by application. Patch fixes the issue by keeping track free DMA channel and configures it in drivers PAN callback so that panned frame from application gets displayed in next frame period. Wiki below describes the issue in detail and it also has link to application with which issue can be reproduced. http://processors.wiki.ti.com/index.php/DA8xx_LCDC_Linux_FB_FAQs Signed-off-by: Nellutla, Aditya <aditya.n@ti.com> Signed-off-by: Manjunathappa, Prakash <prakash.pm@ti.com> Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
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