drm/mcde: Fix display pipeline restart
To make sure that the MCDE is in a reasonable state during set-up, perform a reset by power cycling the block by dropping the on-chip regulator reference after probe. The display subsystem (DSS) has no dedicated reset line so dropping the EPOD regulator is the only real way of resetting it. We introduce code to enable and disable the regulator in the display enable/disable callbacks. We move the generic MCDE setup such as muxing of DPI signals and masking of interrupts to the display handling. When we drop the power to the whole display subsystem, not only MCDE but also the DSI links lose their state. Therefore we move the DSI block reset and hardware initialization code to the mcde_dsi_bridge_pre_enable() callback so this happens every time we start up the bridge, as we may have lost the power. We move the final disablement of the interrupts and clocks to the mcde_dsi_bridge_post_disable() callback rather than have it in the mcde_dsi_bridge_disable() callback, as some control messages may still be sent over the DSI host after the bridge has been shut down. This (together with a patch for the corresponding panel) makes the Samsung GT-S7710 successfully disable and re-enable its display, cutting all power while disabled and re-initializing the hardware when coming back up. Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Cc: newbytee@protonmail.com Cc: Stephan Gerhold <stephan@gerhold.net> Link: https://patchwork.freedesktop.org/patch/msgid/20200808223122.1492124-3-linus.walleij@linaro.org
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