Re: Using LVDS in a iMX6Q/D from Barebox

[Sascha Hauer <s.hauer@pengutronix.de>]

On Fri, Feb 17, 2017 at 04:38:37PM +0100, gianluca wrote:
> On 02/16/2017 04:50 PM, Lucas Stach wrote:
> > Am Donnerstag, den 16.02.2017, 15:43 +0100 schrieb gianluca:
> > > On 02/16/2017 08:28 AM, Sascha Hauer wrote:
> > > > On Wed, Feb 15, 2017 at 03:34:55PM +0100, gianluca wrote:
> > > > > On 02/15/2017 12:51 PM, Sascha Hauer wrote:
> > > > > > On Tue, Feb 14, 2017 at 11:32:44AM +0100, gianluca wrote:
> > > > > > > On 02/10/2017 08:35 AM, Sascha Hauer wrote:
> > > > > If no eeprom is found activate the status of the hdmi node from "disabled"
> > > > > to "okay". So with the same algorithm as above,
> > > > > 
> > > > > Those operations will be done in the coredevice_initcall() level. Is this
> > > > > correct?
> > > > 
> > > > Sounds like a plan. I'm not sure though if you find your EEPROM at
> > > > coredevice_initcall time.
> > > > 
> > > 
> > > Nope. Accessing device drivers (enabled in the device-tree) is possible
> > > in the section: device_initcall() and *NOT* in the coredevice_initcall()
> > > time.
> > > 
> > > Anyway I was wondering if looking for a node in the device-tree, it will
> > > be possible to change the status of that node.
> > > 
> > > in DTS I have
> > > 
> > > &hdmi {
> > > 	status="disabled";
> > > }
> > > 
> > > but I need to set the status to "okay" later on the device_initcall() time.
> > > 
> > > Iterating in the device tree using for_each_node_by_name_from() does not
> > > show any node like hdmi, but using the same function to look for any
> > > "display-timing" section it works.
> > 
> > The node isn't called just "hdmi", that is just the handle, which may
> > not even be present in the final DTB if nothing uses it. The nodes name
> > is "hdmi@0120000".
> > 
> > See "arch/arm/boot/dts/imx6qdl.dtsi".
> > 
> 
> Ok, thank you for hints.
> 
> From my dts file:
> 
> > &hdmi {
> > 	ddc-i2c-bus = <&i2c2>;
> > 	status = "disabled";
> > };
> > 
> 
> It is disabled by default. It will be enabled later by my device_initcall()
> function.
> 
> > &ldb {
> > 	#address-cells = <1>;
> > 	#size-cells = <0>;
> > 	status = "disabled";
> > 
> 
> As the hdmi node.
> 
> > 	lvds0: lvds-channel@0 {
> > 		fsl,data-mapping = "spwg";
> > 		fsl,data-width = <24>;
> > 		status = "disabled";
> > 
> 
> Just for sure it is disabled too!
> 
> 
> > 		display-timings {
> > 			native-mode = <&am128080n3tz>;
> 
> This is fixed. It will be changed during the device_initcall() functions.
> 
> > 			/* DISPLAY 1280x800 AMPIRE AM1280800N3TZ */
> > 			am128080n3tz: am1280800n3tz {
> > 				clock-frequency = <71000000>;
> > 				hactive = <1280>;
> > 				vactive = <800>;
> > 				hback-porch = <50>;
> > 				hfront-porch = <50>;
> > 				vback-porch = <5>;
> > 				vfront-porch = <5>;
> > 				hsync-len = <60>;
> > 				vsync-len = <13>;
> > 				hsync-active = <0>;
> > 				vsync-active = <0>;
> > 				de-active = <1>;
> > 				pixelclk-active = <0>;
> > 			};
> > 			/* DISPLAY 1024x600 AMPIRE AM-1024600LTM LVDS */
> > 			am1024600l: am1024600l {
> > 				clock-frequency = <51200000>;
> > 				hactive = <1024>;
> > 				vactive = <600>;
> > 				hback-porch = <0>;
> > 				hfront-porch = <320>;
> > 				vback-porch = <0>;
> > 				vfront-porch = <35>;
> > 				hsync-len = <1>;
> > 				vsync-len = <1>;
> > 				hsync-active = <0>;
> > 				vsync-active = <0>;
> > 				de-active = <1>;
> > 				pixelclk-active = <0>;
> > 			};
> > 			/* DISPLAY 800x480 */
> > 			ph800480t013: ph800480t013 {
> > 				clock-frequency = <33300000>;
> > 				hactive = <800>;
> > 				vactive = <480>;
> > 				hback-porch = <46>;
> > 				hfront-porch = <210>;
> > 				vback-porch = <23>;
> > 				vfront-porch = <22>;
> > 				hsync-len = <1>;
> > 				vsync-len = <1>;
> > 				hsync-active = <0>;
> > 				vsync-active = <0>;
> > 				de-active = <1>;
> > 				pixelclk-active = <0>;
> > 			};
> > 		};
> > 
> > 		port@4 {
> > 			reg = <4>;
> > 			lvds0_out: endpoint {
> > 				remote-endpoint = <&in_lvds0>;
> > 			};
> > 		};
> > 
> > 	};
> > };
> 
> The device_initcall() functions is looking for an eeprom on the lvds
> channel, and if found it will matched against the native-mode phandle.
> If it is different from the default, a new native-mode will be placed as
> native-mode, and afterall the lvds-channel@0 and ldb will be flagged in
> status as "okay".
> 
> Then the of_device_enable_and_register_by_name("ldb@020e0008") will be
> called.
> 
> In the same way if an eeprom is found on the hdmi connector bus, the hdmi
> status will be changed to "okay".
> 
> If there is no display (so no eeprom either) connected on the lvds
> connector, the device_initcall() functions will let all ldb stuff as default
> (i.e. disabled) and it will enable the hdmi section if there is a hdmi
> display (and its eeprom EDID) connected.
> 
> The problem is the modeset of framebuffer (.num_modes): this list is created
> from the device-tree sequence and the default does not respect the
> native-mode section. i.e. if I have a 800x480 native mode display timing in
> the device tree as a third option, the fb0.modes will have the 800x480 in
> the third place.
> 
> There is a quick (and dirty) way of calling the fb0.mode_name inside a
> device_initcall()?

You can do a setenv("fb0.mode_name", "800x480");

However, it would be nicer to make the native mode the default. struct
display_timings already has a native_mode field, but currently noone is
interested in its value.

Sascha

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