[RFC] drm/lcdc: add TI LCD Controller DRM driver

[Rob Clark]

On Mon, Dec 17, 2012 at 8:39 AM, Rob Clark <robdclark at gmail.com> wrote:
>> I'm not very enthusiastic about adding ti-lcdc specific panel/chip
>> drivers. It's not really a big deal if it's only kernel code, but you
>> add device-tree bindings also, which is an external API that you need to
>> support after adding it.
>>
>> I'd rather see the energy put to common display framework, and get this
>> whole panel/chip driver issue solved in a generic manner.
>
> yeah, I was expecting to migrate to CDF once it exists, but needed
> something for now.  I'm using the exercise to get my thoughts straight
> on how CDF should fit into KMS.  (One thing I plan to add support for
> is an i2c connected hdmi encoder.. which looks like it would fit well
> in drivers/gpu/drm/i2c.. so the drm encoder-slave stuff might be the
> way.)
>
> If you have any suggestions on the DT bindings, I'd like to hear 'em.

btw, a little bit of-topic, but speaking of DT...

Anybody have any clue about how backlight devices are supposed to work
in this brave new DT world?  In the old days, the board file would
stuff a fxn ptr to control backlight in pdata for the driver.  But we
don't have this any more.  I think I need some way to retrieve the
'struct backlight_device' ptr associated with the panel driver, so
that the appropriate dpms fxn ptrs can enable/disable the backlight.

I'm thinking the dt file should have something that looks roughly like:

                /* Settings for CDTech_S035Q01 / LCD3 cape: */
                panel {
                        compatible = "lcdc,panel";
                        pinctrl-names = "default";
                        pinctrl-0 = <&bone_lcd3_cape_lcd_pins>;
                        panel-info {
                                ac-bias           = <255>;
                                ac-bias-intrpt    = <0>;
                                dma-burst-sz      = <16>;
                                bpp               = <16>;
                                fdd               = <0x80>;
                                tft-alt-mode      = <0>;
                                stn-565-mode      = <0>;
                                mono-8bit-mode    = <0>;
                                invert-line-clock = <1>;
                                invert-frm-clock  = <1>;
                                sync-edge         = <0>;
                                sync-ctrl         = <1>;
                                raster-order      = <0>;
                                fifo-th           = <0>;
                        };
                        display-timings {
                                native-mode = <&timing0>;
                                timing0: 320x240 {
                                        hactive         = <320>;
                                        vactive         = <240>;
                                        hback-porch     = <21>;
                                        hfront-porch    = <58>;
                                        hsync-len       = <47>;
                                        vback-porch     = <11>;
                                        vfront-porch    = <23>;
                                        vsync-len       = <2>;
                                        clock-frequency = <8000000>;
                                };
                        };

                        backlight {
                                compatible = "tps65217-backlight";
                                isel = <1>;
                                fdim = <200>;

                                tps = <&tps>;   /* link to the tps */
                                brightness = <100>;
                        };
                };

display-timings is based on the of-videomode helpers patch..
panel-info probably needs to be made to be something more generic, but
we need something to know how to configure the crtc properly..

but I'm not quite sure what to do with the backlight..

BR,
-R