fbdev: ssd1307fb: Unify init code and obtain hw specific bits from DT
The 130X controllers are very similar from the configuration point of view. The configuration registers for the SSD1305/6/7 are bit identical (except the the VHCOM register and the the default values for clock setup register). This patch unifies the init code of the controller and adds hardware specific properties to DT that are needed to correctly initialize the device. The SSD130X can be wired to the OLED panel in various ways. Even for the same controller this wiring can differ from one display module to another and can not be probed by software. The added DT properties reflect these hardware decisions of the display module manufacturer. The 'com-sequential', 'com-lrremap' and 'com-invdir' values define different possibilities for the COM signals pin configuration and readout direction of the video memory. The 'segment-no-remap' allows the inversion of the memory-to-pin mapping ultimately inverting the order of the controllers output pins. The 'prechargepX' values need to be adapted according to the capacitance of the OLEDs pixel cells. So far these hardware specific bits are hard coded in the init code, making the driver usable only for one certain wiring of the controller. This patch makes the driver usable with all possible hardware setups, given a valid hw description in DT. If these values are not set in DT the default values, as they are set in the ssd1307 init code right now, are used. This implies that without the corresponding DT property "segment-no-remap" the segment remap of the ssd130X controller gets activated. Even though this is not the default behaviour according to the datasheet it maintains backward compatibility with older DTBs. Note that the SSD1306 does not seem to be using the configuration written to the registers at all. Therefore this patch does not try to maintain these values without changes in DT. For reference an example is added to the DT bindings documentation that reproduces the configuration that is set in the current init code. Signed-off-by: NThomas Niederprüm <niederp@physik.uni-kl.de> Tested-by: NOlliver Schinagl <o.schinagl@ultimaker.com> Acked-by: NMaxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>
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