Hello, I am happy to see this discussion. I like Noralf's late work to move mipi_dbi to drm/ and remove tinydrm. This helps to simplify implementation and maintenance of drivers for displays that conform to MIPI_DBI set of commands, no matter if they use MIPI_DBI to transfer the image data or not. There are already MIPI_DBI compliant panels in drm/panel, but until Noralf's refactor they needed to implement custom functions (on top SPI) to initialize the display. See the following drivers as examples: - drm/panel/panel-sitronix-st7789v.c - drivers/gpu/drm/panel/panel-tpo-tpg110.c - drivers/gpu/drm/panel/panel-lg-lg4573.c - drivers/gpu/drm/panel/panel-samsung-ld9040.c - drivers/gpu/drm/panel/panel-samsung-s6e63m0.c there may be more... There are also at least two drivers for the same chip ili9341. See: - drm/tinydrm/mi0283qt.c - drm/tinydrm/ili9341.c + another driver for the same chip, but with parallel RGB initial configuration, was submitted I think there should be a single driver supporting all of the chip's capabilities / configurations to avoid maintenance burden and user confusion: As a user, I can see the following use cases if a display conforms to MIPI_DBI. a) it has its internal GRAM and MIPI_DBI can be used to transfer image data b) internal GRAM is not present, parallel RGB must be used to transfer image data c) the display supports both - ili9341 case (but also others available) As a user I want to specify displays that are going to use option a) and/or b) - i.e. I can have multiple ili9341 displays connected to the same parallel RGB MCU interface, but on a different SPI bus (or just different chip_select). The same image data can be transferred to the displays over the parallel RGB or I can switch some of the displays to use the MIPI_DBI (SPI) for different image data transfer. Kind regards Josef Lusticky pá 26. 7. 2019 v 18:14 odesílatel Sam Ravnborg <sam@xxxxxxxxxxxx> napsal: > > Hi Daniel. > > Added Noralf - somehow I missed him on the original mail. > > On Fri, Jul 26, 2019 at 05:06:03PM +0200, Daniel Vetter wrote: > > Also probably should add a few more (drm_bridge) people, I think > > that's also somewhat relevant here. > > -Daniel > > > > On Fri, Jul 26, 2019 at 4:55 PM Daniel Vetter <daniel@xxxxxxxx> wrote: > > > > > > On Fri, Jul 26, 2019 at 02:25:10PM +0200, Sam Ravnborg wrote: > > > > Hi Josef, Daniel et al. > > > > > > > > The driver that triggered this reply is a driver that adds parallel > > > > support to ili9341 in a dedicated panel driver. > > > > The issue here is that we already have a tiny driver that supports the > > > > ili9341 controller - but with a slightly different configuration. > > > > > > > > The ili9341 supports several interfaces - from the datasheet: > > > > "ILI9341 supports parallel 8-/9-/16-/18-bit data bus > > > > MCU interface, 6-/16-/18-bit data bus RGB interface and > > > > 3-/4-line serial peripheral interface (SPI)" > > > > > > > > Noralf - in another mail explained: > > > > " > > > > The MIPI Alliance has lots of standards some wrt. display controller > > > > interfaces: > > > > - MIPI DBI - Display Bus Interface (used for commands and optionally pixels) > > > > - MIPI DPI - Display Pixel Interface (also called RGB interface or > > > > DOTCLK interface) > > > > - MIPI DSI - Display Serial Interface (commands and pixels) > > > > > > > > The ili9341 supports both MIPI DBI and DPI. > > > > " > > > > > > > > MIPI DPI - is a good fit for a drm_panel driver. > > > > MIPI DBI - requires a full display controller driver. > > > > > > > > There are many other examples of driver SoC that in the same way > > > > can be seen only as a panel or as a full display controller driver. > > > > > > > > The open question here is if we should try to support both cases in the > > > > same driver / file. Or shall we implment two different drivers. > > > > One for the panel use-case. And one for the display controller usecase? > > > > > > > > Not sure - so asking for feedback. > > > > > > I'm not sure. Currently we do have DSI and dumb RGB panels all in > > > drm/panel. I don't think we have DBI panels in there yet, but then > > > drm/tiny is the only one supporting these. > > > > > > I guess we could look into move some of the DBI panel drivers into panel > > > drivers, but that needs a bit more glue all around. I'm honestly not sure > > > how the current DSI drivers in drm_panel work exactly, especially for > > > command mode. > > > > > > Or maybe we need a new interface for command mode. > If I get around to do a driver for the ssd1306 then I will try to sewhat > makes sense then. For now we shall not stall the ili9341 driver. > > > > > > Wrt sharing code between drivers for the same chip, but different > > > interfaces: I wouldn't worry too much about that. Maybe try to have a > > > shared header file at least for registers. > This part should be the minimum. Somthing like include/drm/mipi/? > > Sam > > > > Long term we could end up with > > > one driver module which exposes different flavours of the same chip, so > > > multiple drm_panel drivers, or maybe we'll get something more specific for > > > dsi/dbi. > > > -Daniel > > > -- > > > Daniel Vetter > > > Software Engineer, Intel Corporation > > > http://blog.ffwll.ch > > > > > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
