[V2 3/7] video: mmp: fix graphics/video layer enable/mask swap issue

[jett zhou]

2013/6/22 Daniel Drake <dsd at laptop.org>:
> On Mon, Jun 10, 2013 at 9:52 AM, Jett.Zhou <jtzhou at marvell.com> wrote:
>> From: Jing Xiang <jxiang at marvell.com>
>>
>> There is bug when switch dma of graphic layer and video layer, it
>> configured opposite bit, fix it.
>
> So, overlays can be either graphics or video. overlay_is_vid() tells
> you which type.
> overlay_is_vid() makes its decision based on dmafetch_id which is
> undocumented and I don't understand it (and in another mail you said
> this is legacy configuration that is going to be removed).
>
> Ignoring my lack of understanding of the background: the patch here
> seems to make the code more correct. It will modify the path's
> underlying control register to enable graphics or video transfer
> depending on the overlay type. Turning a graphics overlay dmafetch ON
> will not stomp on the bits set by any video overlay dmafetch on the
> same path. Previously the logic was reversed.
>
> This codepath will not work correctly if there will ever be more than
> one overlay of the same type on the same path. For example, if we have
> two graphics overlays;
> 1. dmafetch_onoff(overlay1, on) - graphics transfer is now enabled in
> the hardware
> 2. dmafetch_onoff(overlay2, on) - graphics transfer was already
> enabled, no change
> 3. dmafetch_onoff(overlay2, off) - graphics transfer is now disabled
> in the hardware
>
> At this point overlay1 is still active in theory, but the driver has
> disabled graphics transfer at the hardware level.
>
> Daniel
Hi Daniel
     Now for our controller and usage, we have 2 over-lay of the path,
they are graphic layer and video layer.
     dmafetch_id =0 if it is graphic layer, dmafetch_id =1 if it is video layer.
     The another mail mentioned is right, we plan to remove the
dmafetch_id and detect overlay_is_vid by other method.
     But this patch did not include it yet, it will be included by
another patch later on.
Thanks


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Best Regards
Jett Zhou