On Sun, Mar 12, 2017 at 06:50:17PM +0100, Daniel Vetter wrote: > Hi Noralf, > > On Sat, Mar 11, 2017 at 10:35:31PM +0100, Noralf Trønnes wrote: > > Add support for displays that have a register interface and can be > > operated using a simple vtable. > > > > I have looked through the staging/fbtft drivers and it seems that, > > except the MIPI controllers, most if not all controllers are operated > > through a register. And since most controllers have more than one bus > > interface option, regmap seems like a good choice to describe the > > interface (tested[1,2]). > > MIPI DCS can't be represented using regmap since some commands doesn't > > have a parameter. That would be like a register without a value, which > > doesn't make sense. > > > > In my second RFC of tinydrm I used drm_panel to decribe the panels > > since it was a good match to the fbtft displays. I was then told that > > drm_panel wasn't supposed to used like that, so I dropped it and have > > tried to use the drm_simple_display_pipe_funcs vtable directly. This > > hasn't been all successful, since I ended up using devm_add_action() to > > power down the controller at the right time. Thierry Reding wasn't > > happy with this and suggested "to add an explicit callback somewhere". > > My solution has been to copy the drm_panel_funcs vtable. > > Since I now have a vtable, I also added a callback to flush the > > framebuffer. So presumably all the fbtft drivers can now be operated > > through the tinydrm_panel_funcs vtable. > > Ehrm, what? I admit I didn't follow the discussion in-depth, but if > drm_panel can't be used to describe a panel, it's not fit for the job and > needs to be extended. Adding even more abstraction, matroschka-style, > isn't a solution. > > Personally I think tinydrm itself is already a bit much wrapping, but I > see that for really simple drivers it has it's uses. But more layers feels > like going in the wrong direction. > > For the callback you're looking for (i.e. the regulator_disable call) I > think the correct place is to enable/disable the regulator in the > enable/disable hooks of the drm_simple_display_pipe functions. Or maybe in > their equivalent in drm_panel (well, probably pre_enable and post_disable, > since I guess you need that regulator to driver anything). Same for _init, > if the display is completely off there's no point in keeping the hw > running. Enabling/disabling the entire hw is pretty much what ->enable and > ->disable are for. This also gives you proper runtime pm for almost for > free ... > > Also, since the regulator is actually stored in struct mipi_dbi, it's > probably best to handle it in the mipi_dbi helpers too. You do that > already with the backlight anyway. > > I noticed that the version of tinydrm that landed doesn't use drm_panel > anymore, I thought that was the case once, and for the version I acked? Self-correct, there never was a version with drm_panel. tbh I think that's perfectly fine, tinydrm is aimed at simple panels behind spi/i2c buses (where also the entire video data is uploaded through spi/i2c, not just control information). Not changing anything like I recommend seems like the right action still (well, shuffling the regulator into simple_pipe->enable/disable like I think it should be). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
