Re: [PATCH] drm/omap: dsi: Fix PM for display blank with paired dss_pll calls

[Tony Lindgren <tony@atomide.com>]

* Tomi Valkeinen <tomi.valkeinen@ti.com> [190205 11:07]:
> Yep... So there's the DSI internal code which needs to deal with ulps
> and disconnect_lanes, and then the external interface to the DSI PLL (so
> that DPI can use DSI PLL) without ulps/disconnect.
> 
> I think your patch breaks this latter one, as disconnect_lanes is zero
> in that case and would leave the regulator enabled. This would probably
> be visible on e.g. Pandaboard, which uses DSI PLLs for the TFP410 DVI
> output, if I recall right.

Sorry I don't quite follow what happens there with dvi
calling into dsi.. Care to describe a bit more?

> And storing the 'disconnect_lanes' is a bit ugly, but I don't see right
> away how to avoid it...
> 
> Maybe the field in dsi_data should be something like
> "keep_lanes_powered", and default value false. In
> dsi_display_uninit_dsi(), we could set
> 
> keep_lanes_powered = !disconnect_lanes;
> 
> and after dss_pll_disable() call, set keep_lanes_powered back to false
> to keep it in the default state.

If we need more control over the lanes, maybe we should just
add a helper like this so that only panels that need it can
call it:

static int dsi_set_lane_power(struct omap_dss_device *dssdev,
			      bool enable)
{
        struct dsi_data *dsi = to_dsi_data(dssdev);

        dsi->keep_lanes_powered = enable;

        return 0;
}

Regards,

Tony
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