Re: [PATCH 4/4] omapdss: features: fixed supported outputs for OMAP4

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 2013-03-12 16:01, Archit Taneja wrote:
> On Tuesday 12 March 2013 07:07 PM, Tomi Valkeinen wrote:

>> So, I don't disagree with you. But I don't quite understand why we could
>> not use the fixed channels for now? They should work in all the boards
>> we have, right? Or is there something with DRM that forces the driver to
>> select the channel dynamically?
> 
> I think we can use fixed channels, but if the number of different fixed
> channels crosses the number of crtcs the kernel wants, then we would
> need to atleast change the channels of some of the outputs.
> 
> For example, suppose omapdrm is asked to use only 2 crtcs, and it picks
> up LCD2 and TV managers. Now if there is some panel which says it's
> recommended channel is LCD, then things won't work.

Are you saying omapdrm picks the managers for the crtcs before knowing
what panels there are? That can't work right... We need to know what
outputs are to be used before we can select the managers. Or, we always
need crtcs for all the managers.

If we do know the panels, and thus outputs, then the managers to be used
are found easily from output->dispc_channel.

But, of course, the crtc to manager mapping could be changed (if omapdrm
supports this). If omapdrm is asked to use only 1 crtc, but there are
two panels, then only one panel can be used at a time, and the manager
for the crtc needs to be changed when the panel to be used is changed.
But even in this case used manager is clear, it comes from
output->dispc_channel.

> At the moment, omapdrm maps a crtc with a manger using a function called
> pipe2chan() which just selects a manager with the biggest channel no. So
> if the kernel is configured to have num_crtcs as 1. The single crtc will
> be mapped to LCD2. This method is wrong, as it doesn't even look at the
> type of panels at all. For an omap5 panda, the most suitable manager to
> map to the crtc would be TV(for hdmi).
> 
> I think what we probably need to do is to combine both the methods. I.e,
> make each output connectible to only one channel, and also iterate
> through the panels in omapdrm to find the most suitable channels. So in
> my patch, instead of looking at all the supported managers for an
> output(checking with dss_feat_get_supported_outputs() on each manager),
> I just look at the recommended channel, and try to map that manager.

I don't know, I feel like I'm not understanding something here =).

 Tomi



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