Hi, On Tue, 17 Oct 2017 14:45:04 +0200 Thierry Reding wrote: > On Tue, Oct 17, 2017 at 02:25:07PM +0200, Lothar Waßmann wrote: > > Hi, > > > > On Tue, 17 Oct 2017 14:14:22 +0200 Thierry Reding wrote: > > > On Wed, Oct 11, 2017 at 01:23:36PM +0200, Lothar Waßmann wrote: > > > > The Ka-Ro electronics MB7 baseboard has an on-board LCD->LVDS > > > > converter that requires a fixed pixelclk polarity, no matter what the > > > > panel's display_mode specifies. Add an option to override the pixelclk > > > > polarity defined in the panel's display_mode via DTB. > > > > > > I'd argue that the LCD->LVDS converter should be modelled specifically > > > in DT to handle this case. It could be a implemented as a DRM bridge > > > driver, for example. > > > > > IMO that's just overkill for a simple chip that is in no way > > configurable nor detectable by software. > > I suspect that you're not the only one who runs a board that has this > kind of quirk. If we solve this in a generic way we can point people in > that direction when they come asking for such a quirk. > > So this could be something very simple that's instantiated using maybe a > couple of lines of code. > I found the drivers/gpu/drm/bridge/lvds-encoder.c driver which on first glance is more or less what I would need. But the driver is currently dysfunctional due to: |commit 13dfc0540a575b47b2d640b093ac16e9e09474f6 |Author: Eric Anholt <eric@xxxxxxxxxx> |Date: Fri Jun 2 13:25:14 2017 -0700 | | drm/bridge: Refactor out the panel wrapper from the lvds-encoder bridge. Also there is no in-kernel user of this driver, so that it obviously doesn't get tested in any way. There is only one dts file (r8a7779-marzen.dts) that instantiate this driver, but it has an incomplete OF graph. The missing link for the OF graph is provided by either r8a77xx-aa104xd12-panel.dtsi or r8a77xx-aa121td01-panel.dtsi, but those files are referenced nowhere in the kernel source. Reverting the part of the above mentioned patch that touches lvds-encoder.c makes the driver functional, but I see no way to use this driver to enforce specific bus_flags for the interface, since the code is run prior to the simple-panel's initialization, which would override whatever settings might have been provided by the lvds-encoder driver. Can someone enligthen me, how to enforce specific bus_flags/bus_format settings for an LCD interface driven by the simple-panel driver apart from doing it in the simple-panel driver itself? Lothar Waßmann -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
