imx-drm: ldb and display power on sequence

imx-drm: ldb and display power on sequence

[Christian Gmeiner]

Hi all.

On our custom board design (imx6d) we are using a TFT-display
connceted via LVDS.
The datasheet [0] says that the display needs a defined power up
sequence. I need
to control the following stuff:

- LCD_ON (gpio2 3)
- Backlight ON (gpio2 0)
- PMW for dimm

At the moment I have the backlight suff ready:

       backlight {
               compatible = "pwm-backlight";
               pwms = <&pwm4 0 50000>;
               enable-gpios = <&gpio2 0 0>;

               brightness-levels = <0 1 2 3 4>;
               default-brightness-level = <4>;
       };

Now I only need to enable the LCD_ON and wait 40ms before turning on
the LVDS clocks and data. For this I tought
to add a regulator support in imx_ldb_encoder_commit(..) of imx-ldb.c.
That should give me the correct sequence for
LVDS on to LVDS data/clock. Now I only need to get the pwm-backlight
driver doing its work after ldb is ready.

Are there some other and better solutions to this problem?

[0] http://www.hy-line.de/fileadmin/hy-line/computer/csv/datasheets/FG050722DSSWDG01.pdf

thanks
--
Christian Gmeiner, MSc

https://soundcloud.com/christian-gmeiner

imx-drm: ldb and display power on sequence

[Philipp Zabel]

Hi Christian,

Am Donnerstag, den 06.03.2014, 13:34 +0100 schrieb Christian Gmeiner:
> Hi all.
> 
> On our custom board design (imx6d) we are using a TFT-display
> connceted via LVDS.
> The datasheet [0] says that the display needs a defined power up
> sequence. I need
> to control the following stuff:
> 
> - LCD_ON (gpio2 3)
> - Backlight ON (gpio2 0)
> - PMW for dimm
> 
> At the moment I have the backlight suff ready:
> 
>        backlight {
>                compatible = "pwm-backlight";
>                pwms = <&pwm4 0 50000>;
>                enable-gpios = <&gpio2 0 0>;
> 
>                brightness-levels = <0 1 2 3 4>;
>                default-brightness-level = <4>;
>        };
> 
> Now I only need to enable the LCD_ON and wait 40ms before turning on
> the LVDS clocks and data.

This can be done by adding a regulator-enable-ramp-delay property to the
gpio regulator.

> For this I tought to add a regulator support in
> imx_ldb_encoder_commit(..) of imx-ldb.c.
>That should give me the correct sequence for
> LVDS on to LVDS data/clock. Now I only need to get the pwm-backlight
> driver doing its work after ldb is ready.

We should rather add drm_panel support to imx-ldb. I have just sent a
patch for this.
The simple-panel driver already supports regulator and backlight.

regards
Philipp

imx-drm: ldb and display power on sequence

[Christian Gmeiner]

Hi Philipp,

> Am Donnerstag, den 06.03.2014, 13:34 +0100 schrieb Christian Gmeiner:
>> Hi all.
>>
>> On our custom board design (imx6d) we are using a TFT-display
>> connceted via LVDS.
>> The datasheet [0] says that the display needs a defined power up
>> sequence. I need
>> to control the following stuff:
>>
>> - LCD_ON (gpio2 3)
>> - Backlight ON (gpio2 0)
>> - PMW for dimm
>>
>> At the moment I have the backlight suff ready:
>>
>>        backlight {
>>                compatible = "pwm-backlight";
>>                pwms = <&pwm4 0 50000>;
>>                enable-gpios = <&gpio2 0 0>;
>>
>>                brightness-levels = <0 1 2 3 4>;
>>                default-brightness-level = <4>;
>>        };
>>
>> Now I only need to enable the LCD_ON and wait 40ms before turning on
>> the LVDS clocks and data.
>
> This can be done by adding a regulator-enable-ramp-delay property to the
> gpio regulator.
>

Correct.

>> For this I tought to add a regulator support in
>> imx_ldb_encoder_commit(..) of imx-ldb.c.
>>That should give me the correct sequence for
>> LVDS on to LVDS data/clock. Now I only need to get the pwm-backlight
>> driver doing its work after ldb is ready.
>
> We should rather add drm_panel support to imx-ldb. I have just sent a
> patch for this.
> The simple-panel driver already supports regulator and backlight.
>

I am still life in the world of a stable kernel called 3.13.6 :) Will
backport the simple-panel driver
and will have a look at your patches - today.

greets
--
Christian Gmeiner, MSc

https://soundcloud.com/christian-gmeiner

imx-drm: ldb and display power on sequence

[Christian Gmeiner]

2014-03-07 12:18 GMT+01:00 Christian Gmeiner <christian.gmeiner@gmail.com>:
> Hi Philipp,
>
>> Am Donnerstag, den 06.03.2014, 13:34 +0100 schrieb Christian Gmeiner:
>>> Hi all.
>>>
>>> On our custom board design (imx6d) we are using a TFT-display
>>> connceted via LVDS.
>>> The datasheet [0] says that the display needs a defined power up
>>> sequence. I need
>>> to control the following stuff:
>>>
>>> - LCD_ON (gpio2 3)
>>> - Backlight ON (gpio2 0)
>>> - PMW for dimm
>>>
>>> At the moment I have the backlight suff ready:
>>>
>>>        backlight {
>>>                compatible = "pwm-backlight";
>>>                pwms = <&pwm4 0 50000>;
>>>                enable-gpios = <&gpio2 0 0>;
>>>
>>>                brightness-levels = <0 1 2 3 4>;
>>>                default-brightness-level = <4>;
>>>        };
>>>
>>> Now I only need to enable the LCD_ON and wait 40ms before turning on
>>> the LVDS clocks and data.
>>
>> This can be done by adding a regulator-enable-ramp-delay property to the
>> gpio regulator.
>>
>
> Correct.
>
>>> For this I tought to add a regulator support in
>>> imx_ldb_encoder_commit(..) of imx-ldb.c.
>>>That should give me the correct sequence for
>>> LVDS on to LVDS data/clock. Now I only need to get the pwm-backlight
>>> driver doing its work after ldb is ready.
>>
>> We should rather add drm_panel support to imx-ldb. I have just sent a
>> patch for this.
>> The simple-panel driver already supports regulator and backlight.
>>
>
> I am still life in the world of a stable kernel called 3.13.6 :) Will
> backport the simple-panel driver
> and will have a look at your patches - today.
>

I backported your patch and updated my dts file. It looks better now
but one thing is does not work.
The datasheet says I need to enable the lcd, enable LVDS data and then
I can enable the backlight.
With the simple panel following happens:

panel_simple_enable:
- regulator_enable(p->supply);
- gpio_set_value
- backlight_update_status

The result of this sequence are graphical glitches and a ghost picture
on the panel. Need to think
about it to find a good solution for it. Maybe there should be a 2 way
init phase for a panel.
- preinit - turn on power-supply and set gpio
- init ipu
- postinit - unblank backlight

--
Christian Gmeiner, MSc

https://soundcloud.com/christian-gmeiner

imx-drm: ldb and display power on sequence

[Christian Gmeiner]

2014-03-11 9:51 GMT+01:00 Christian Gmeiner <christian.gmeiner@gmail.com>:
> 2014-03-07 12:18 GMT+01:00 Christian Gmeiner <christian.gmeiner@gmail.com>:
>> Hi Philipp,
>>
>>> Am Donnerstag, den 06.03.2014, 13:34 +0100 schrieb Christian Gmeiner:
>>>> Hi all.
>>>>
>>>> On our custom board design (imx6d) we are using a TFT-display
>>>> connceted via LVDS.
>>>> The datasheet [0] says that the display needs a defined power up
>>>> sequence. I need
>>>> to control the following stuff:
>>>>
>>>> - LCD_ON (gpio2 3)
>>>> - Backlight ON (gpio2 0)
>>>> - PMW for dimm
>>>>
>>>> At the moment I have the backlight suff ready:
>>>>
>>>>        backlight {
>>>>                compatible = "pwm-backlight";
>>>>                pwms = <&pwm4 0 50000>;
>>>>                enable-gpios = <&gpio2 0 0>;
>>>>
>>>>                brightness-levels = <0 1 2 3 4>;
>>>>                default-brightness-level = <4>;
>>>>        };
>>>>
>>>> Now I only need to enable the LCD_ON and wait 40ms before turning on
>>>> the LVDS clocks and data.
>>>
>>> This can be done by adding a regulator-enable-ramp-delay property to the
>>> gpio regulator.
>>>
>>
>> Correct.
>>
>>>> For this I tought to add a regulator support in
>>>> imx_ldb_encoder_commit(..) of imx-ldb.c.
>>>>That should give me the correct sequence for
>>>> LVDS on to LVDS data/clock. Now I only need to get the pwm-backlight
>>>> driver doing its work after ldb is ready.
>>>
>>> We should rather add drm_panel support to imx-ldb. I have just sent a
>>> patch for this.
>>> The simple-panel driver already supports regulator and backlight.
>>>
>>
>> I am still life in the world of a stable kernel called 3.13.6 :) Will
>> backport the simple-panel driver
>> and will have a look at your patches - today.
>>
>
> I backported your patch and updated my dts file. It looks better now
> but one thing is does not work.
> The datasheet says I need to enable the lcd, enable LVDS data and then
> I can enable the backlight.
> With the simple panel following happens:
>
> panel_simple_enable:
> - regulator_enable(p->supply);
> - gpio_set_value
> - backlight_update_status
>
> The result of this sequence are graphical glitches and a ghost picture
> on the panel. Need to think
> about it to find a good solution for it. Maybe there should be a 2 way
> init phase for a panel.
> - preinit - turn on power-supply and set gpio
> - init ipu
> - postinit - unblank backlight
>

Okay... I am getting everything to work as expected but I am using
some hacks, which I hope to get
rid of. There is one simple 'problem' with my pwm-backlight.

        backlight: backlight {
                compatible = "pwm-backlight";
                pwms = <&pwm4 0 50000>;
                enable-gpios = <&gpio2 0 0>;

                brightness-levels = <0 1 ... 100>
                default-brightness-level = <100>;
        };

        panel: panel {
                compatible = "simple-panel";
                power-supply = <&reg_lcd_on>;
                backlight = <&backlight>;
        };

The pwn-backlight driver gets loaded before imx-drm/simple panel
dirver. The result is that the backlight
gets turned on but the whole drm subsystem is not ready -> gohst
picture from last reboot get shown.
At the moment I removed the backlight_update_status(bl); call from the
pwm-backlight driver (probe function).
Is there a better way to do it?

greets
--
Christian Gmeiner, MSc

https://soundcloud.com/christian-gmeiner