[PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Robert Jarzmik]

Add documentation for the PXA frambuffer devicetree binding.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
Since v1: Philipp's review on the whole binding
---
 .../devicetree/bindings/video/marvell,pxafb.txt    | 80 ++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/video/marvell,pxafb.txt

diff --git a/Documentation/devicetree/bindings/video/marvell,pxafb.txt b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
new file mode 100644
index 000000000000..4d6bd490680d
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
@@ -0,0 +1,80 @@
+PXA LCDC Framebuffer
+--------------------
+
+Required properties:
+ - compatible :
+	"marvell,pxa2xx-lcdc",
+ - reg : Should contain 1 register ranges(address and length).
+	 Can contain an additional register range(address and length)
+	 for fixed framebuffer memory. Useful for dedicated memories.
+ - interrupts : framebuffer controller interrupt
+
+Required nodes:
+ - clocks: phandle to input clocks.
+ - port: connection to the LCD panel (see video-interfaces.txt)
+	 This nodes must have its properties bus-width and remote-endpoint set.
+	 This should be in the board dts.
+
+Example:
+
+	lcd-controller@40500000 {
+		compatible = "marvell,pxa2xx-lcdc";
+		reg = <0x44000000 0x10000>;
+		interrupts = <17>;
+		clocks = <&clks CLK_LCD>;
+		interrupts = <23>;
+		status = "okay";
+
+		port {
+			lcdc_out: endpoint {
+				remote-endpoint = <&panel_in>;
+				bus-width = <16>;
+			};
+		};
+	};
+
+PXA LCDC Display
+----------------
+Required properties (as per of_videomode_helper):
+ - lcd-type: either "mono-stn", "mono-dstn", "color-stn", "color-dstn",
+		    "color-tft", "smart-panel"
+
+Optional properties (as per of_videomode_helper):
+ - power-supply: power supply regulator to the LCD to power it on or off
+		 (see regulator.txt)
+ - backlight: backlight control (see backlight.txt)
+
+Required nodes:
+ - port: connection to the LCD controller
+ - display-timings: panel timings (see display-timing.txt)
+
+Example:
+	panel {
+		compatible = "toshiba,ltm0305a776";
+		lcd-type = "color-tft";
+
+		power-supply = <&lcd_supply>;
+		backlight = <&lcd_backlight>;
+
+		port {
+			panel_in: endpoint {
+				remote-endpoint = <&lcdc_out>;
+			};
+		};
+
+		display-timings {
+			native-mode = <&timing0>;
+			timing0: 240p {
+				/* 240x320p24 */
+				clock-frequency = <4545000>;
+				hactive = <240>;
+				vactive = <320>;
+				hfront-porch = <4>;
+				hback-porch = <6>;
+				hsync-len = <4>;
+				vback-porch = <5>;
+				vfront-porch = <3>;
+				vsync-len = <2>;
+			};
+		};
+	};
-- 
2.1.4

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Philipp Zabel]

On Sun, Oct 4, 2015 at 12:31 PM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
> Add documentation for the PXA frambuffer devicetree binding.
>
> Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
> ---
> Since v1: Philipp's review on the whole binding
> ---
>  .../devicetree/bindings/video/marvell,pxafb.txt    | 80 ++++++++++++++++++++++
>  1 file changed, 80 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/video/marvell,pxafb.txt
>
> diff --git a/Documentation/devicetree/bindings/video/marvell,pxafb.txt b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
> new file mode 100644
> index 000000000000..4d6bd490680d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
> @@ -0,0 +1,80 @@
> +PXA LCDC Framebuffer
> +--------------------
> +
> +Required properties:
> + - compatible :
> +       "marvell,pxa2xx-lcdc",
> + - reg : Should contain 1 register ranges(address and length).
> +        Can contain an additional register range(address and length)
> +        for fixed framebuffer memory. Useful for dedicated memories.
> + - interrupts : framebuffer controller interrupt
> +
> +Required nodes:
> + - clocks: phandle to input clocks.
> + - port: connection to the LCD panel (see video-interfaces.txt)
> +        This nodes must have its properties bus-width and remote-endpoint set.
> +        This should be in the board dts.
> +
> +Example:
> +
> +       lcd-controller@40500000 {
> +               compatible = "marvell,pxa2xx-lcdc";
> +               reg = <0x44000000 0x10000>;
> +               interrupts = <17>;
> +               clocks = <&clks CLK_LCD>;
> +               interrupts = <23>;

The interrupt line is duplicated in the example.

> +               status = "okay";
> +
> +               port {
> +                       lcdc_out: endpoint {
> +                               remote-endpoint = <&panel_in>;
> +                               bus-width = <16>;
> +                       };
> +               };
> +       };
> +
> +PXA LCDC Display
> +----------------
> +Required properties (as per of_videomode_helper):
> + - lcd-type: either "mono-stn", "mono-dstn", "color-stn", "color-dstn",
> +                   "color-tft", "smart-panel"

Would it make sense to make this property optional and have the
default be "color-tft"? That is probably the most common one by far.

regards
Philipp

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Robert Jarzmik]

Philipp Zabel <philipp.zabel@gmail.com> writes:

> On Sun, Oct 4, 2015 at 12:31 PM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
>> +       lcd-controller@40500000 {
>> +               compatible = "marvell,pxa2xx-lcdc";
>> +               reg = <0x44000000 0x10000>;
>> +               interrupts = <17>;
>> +               clocks = <&clks CLK_LCD>;
>> +               interrupts = <23>;
>
> The interrupt line is duplicated in the example.
Indeed, I'll fix that.
>
>> +               status = "okay";
>> +
>> +               port {
>> +                       lcdc_out: endpoint {
>> +                               remote-endpoint = <&panel_in>;
>> +                               bus-width = <16>;
>> +                       };
>> +               };
>> +       };
>> +
>> +PXA LCDC Display
>> +----------------
>> +Required properties (as per of_videomode_helper):
>> + - lcd-type: either "mono-stn", "mono-dstn", "color-stn", "color-dstn",
>> +                   "color-tft", "smart-panel"
>
> Would it make sense to make this property optional and have the
> default be "color-tft"? That is probably the most common one by far.
Yes, sure, let's do it that way for v3.

Cheers.

-- 
Robert

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Rob Herring]

On Sun, Oct 4, 2015 at 5:31 AM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
> Add documentation for the PXA frambuffer devicetree binding.

Strictly speaking this is a binding for PXA display controller, not a
Linux FB driver. There are lots of "framebuffer" and "DRM" bindings
which I'm trying to curb.

> Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
> ---
> Since v1: Philipp's review on the whole binding
> ---
>  .../devicetree/bindings/video/marvell,pxafb.txt    | 80 ++++++++++++++++++++++

Please put in bindings/display/ as I'm consolidating all the display
related bindings there[1].

>  1 file changed, 80 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/video/marvell,pxafb.txt
>
> diff --git a/Documentation/devicetree/bindings/video/marvell,pxafb.txt b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
> new file mode 100644
> index 000000000000..4d6bd490680d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
> @@ -0,0 +1,80 @@
> +PXA LCDC Framebuffer
> +--------------------
> +
> +Required properties:
> + - compatible :
> +       "marvell,pxa2xx-lcdc",

No differences in h/w for any of the chips?

> + - reg : Should contain 1 register ranges(address and length).
> +        Can contain an additional register range(address and length)
> +        for fixed framebuffer memory. Useful for dedicated memories.

This is memory that can't be used for anything else? We already have
reserved-memory for this if it is just RAM. There's also a binding for
on-chip SRAM which should probably be used if the memory is usable for
other things.

> + - interrupts : framebuffer controller interrupt
> +
> +Required nodes:
> + - clocks: phandle to input clocks.
> + - port: connection to the LCD panel (see video-interfaces.txt)
> +        This nodes must have its properties bus-width and remote-endpoint set.
> +        This should be in the board dts.
> +
> +Example:
> +
> +       lcd-controller@40500000 {
> +               compatible = "marvell,pxa2xx-lcdc";
> +               reg = <0x44000000 0x10000>;
> +               interrupts = <17>;
> +               clocks = <&clks CLK_LCD>;
> +               interrupts = <23>;
> +               status = "okay";
> +
> +               port {
> +                       lcdc_out: endpoint {
> +                               remote-endpoint = <&panel_in>;
> +                               bus-width = <16>;
> +                       };
> +               };
> +       };
> +
> +PXA LCDC Display

This should not be specific to PXA, but for this panel. This should be
in bindings/display/panel/.

> +----------------
> +Required properties (as per of_videomode_helper):
> + - lcd-type: either "mono-stn", "mono-dstn", "color-stn", "color-dstn",
> +                   "color-tft", "smart-panel"
> +
> +Optional properties (as per of_videomode_helper):
> + - power-supply: power supply regulator to the LCD to power it on or off
> +                (see regulator.txt)
> + - backlight: backlight control (see backlight.txt)
> +
> +Required nodes:
> + - port: connection to the LCD controller
> + - display-timings: panel timings (see display-timing.txt)

If lcd-type is smart-panel, then this node would not make sense.

> +
> +Example:
> +       panel {
> +               compatible = "toshiba,ltm0305a776";
> +               lcd-type = "color-tft";
> +
> +               power-supply = <&lcd_supply>;
> +               backlight = <&lcd_backlight>;
> +
> +               port {
> +                       panel_in: endpoint {
> +                               remote-endpoint = <&lcdc_out>;
> +                       };
> +               };
> +
> +               display-timings {
> +                       native-mode = <&timing0>;
> +                       timing0: 240p {
> +                               /* 240x320p24 */
> +                               clock-frequency = <4545000>;
> +                               hactive = <240>;
> +                               vactive = <320>;
> +                               hfront-porch = <4>;
> +                               hback-porch = <6>;
> +                               hsync-len = <4>;
> +                               vback-porch = <5>;
> +                               vfront-porch = <3>;
> +                               vsync-len = <2>;
> +                       };
> +               };
> +       };
> --
> 2.1.4
>

[1] https://lkml.org/lkml/2015/10/1/899

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Robert Jarzmik]

Rob Herring <robh@kernel.org> writes:

> On Sun, Oct 4, 2015 at 5:31 AM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
>> Add documentation for the PXA frambuffer devicetree binding.
>
> Strictly speaking this is a binding for PXA display controller, not a
> Linux FB driver. There are lots of "framebuffer" and "DRM" bindings
> which I'm trying to curb.
Yes, that's very true. That deserves a new commit message and a new file name
(marvell,pxa2xx-lcd).
>>  .../devicetree/bindings/video/marvell,pxafb.txt    | 80 ++++++++++++++++++++++
>
> Please put in bindings/display/ as I'm consolidating all the display
> related bindings there[1].
Of course, for v3.

>> +++ b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
>> @@ -0,0 +1,80 @@
>> +PXA LCDC Framebuffer
>> +--------------------
>> +
>> +Required properties:
>> + - compatible :
>> +       "marvell,pxa2xx-lcdc",
>
> No differences in h/w for any of the chips?
All pxa25x, pxa27x and pxa3xx are compatible.
AFAIK, pxa3xx has an IP with additional registers. But :
 - these (this) register(s) is not necessary for the display controller to work
   (it's more a control to shift red/green/blue values, and energy management)
 - all the registers in pxa2{5,7}x are the same in pxa3xx

The pxafb driver acts today on the subset of registers which are the same across
all pxaXXX variants. This is what made me think only one compatible property was
required.

If I'm wrong, I could add "marvell,pxa3xx-lcdc", is that what you think I should
do ?
>
>> + - reg : Should contain 1 register ranges(address and length).
>> +        Can contain an additional register range(address and length)
>> +        for fixed framebuffer memory. Useful for dedicated memories.
>
> This is memory that can't be used for anything else? We already have
> reserved-memory for this if it is just RAM. There's also a binding for
> on-chip SRAM which should probably be used if the memory is usable for
> other things.
That is a wrong copy paste I made. I was more thinking of having only 1 register
range, and no video memory reservation ...

>> +PXA LCDC Display
>
> This should not be specific to PXA, but for this panel. This should be
> in bindings/display/panel/.
Sure, for v3.

>> +----------------
>> +Required properties (as per of_videomode_helper):
>> + - lcd-type: either "mono-stn", "mono-dstn", "color-stn", "color-dstn",
>> +                   "color-tft", "smart-panel"
>> +
>> +Optional properties (as per of_videomode_helper):
>> + - power-supply: power supply regulator to the LCD to power it on or off
>> +                (see regulator.txt)
>> + - backlight: backlight control (see backlight.txt)
>> +
>> +Required nodes:
>> + - port: connection to the LCD controller
>> + - display-timings: panel timings (see display-timing.txt)
>
> If lcd-type is smart-panel, then this node would not make sense.
Ah I see, so this could be optional maybe ?

Actually when I'll move the panel definition to bindings/display/panel, is this
what I should do :
 - create a file marvell,pxa2xx-panel
 - input all these properties into this file

And then, when a board maintainer will create a devicetree description, he will
write something like :
      compatible = "toshiba,ltm0305a776";
      compatible = "marvell,pxa2xx-panel";
      lcd-type = "color-tft";
      ...

If that's the case, I wonder how to "enforce" that a panel used with
marvell,pxa2xx-lcdc (through the of_graph 'port' node) be compatible with
marvell,pxa2xx-panel ?

Cheers.

-- 
Robert

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Philipp Zabel]

On Tue, Oct 6, 2015 at 9:32 PM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
> Rob Herring <robh@kernel.org> writes:
>>> +       "marvell,pxa2xx-lcdc",
>>
>> No differences in h/w for any of the chips?
> All pxa25x, pxa27x and pxa3xx are compatible.
> AFAIK, pxa3xx has an IP with additional registers. But :
>  - these (this) register(s) is not necessary for the display controller to work
>    (it's more a control to shift red/green/blue values, and energy management)
>  - all the registers in pxa2{5,7}x are the same in pxa3xx

So the pxa3xx is pxa2xx compatible. The pxa3xx device tree should
contain compatible = "marvell,pxa3xx-lcdc", "marvell,pxa2xx-lcdc";

That way we can just ignore the pxa3xx compatible value until the need
arises to do something different with the additional registers, and if
that happens we already have it in the device trees.

>> If lcd-type is smart-panel, then this node would not make sense.
> Ah I see, so this could be optional maybe ?
>
> Actually when I'll move the panel definition to bindings/display/panel, is this
> what I should do :
>  - create a file marvell,pxa2xx-panel
>  - input all these properties into this file
>
> And then, when a board maintainer will create a devicetree description, he will
> write something like :
>       compatible = "toshiba,ltm0305a776";
>       compatible = "marvell,pxa2xx-panel";
>       lcd-type = "color-tft";
>       ...
>
> If that's the case, I wonder how to "enforce" that a panel used with
> marvell,pxa2xx-lcdc (through the of_graph 'port' node) be compatible with
> marvell,pxa2xx-panel ?

I think we should move to use drm simple-panel as soon as possible,
but until this information can be derived from the compatible string,
it should maybe stay contained to the lcdc node. At least I don't
think adding a marvell panel compatible is a solution. Maybe this
could be generalized and added as an optional property to the
simple-panel bindings.

regards
Philipp

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Rob Herring]

On Tue, Oct 6, 2015 at 2:32 PM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
> Rob Herring <robh@kernel.org> writes:
>
>> On Sun, Oct 4, 2015 at 5:31 AM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
>>> Add documentation for the PXA frambuffer devicetree binding.
>>
>> Strictly speaking this is a binding for PXA display controller, not a
>> Linux FB driver. There are lots of "framebuffer" and "DRM" bindings
>> which I'm trying to curb.
> Yes, that's very true. That deserves a new commit message and a new file name
> (marvell,pxa2xx-lcd).
>>>  .../devicetree/bindings/video/marvell,pxafb.txt    | 80 ++++++++++++++++++++++
>>
>> Please put in bindings/display/ as I'm consolidating all the display
>> related bindings there[1].
> Of course, for v3.
>
>>> +++ b/Documentation/devicetree/bindings/video/marvell,pxafb.txt
>>> @@ -0,0 +1,80 @@
>>> +PXA LCDC Framebuffer
>>> +--------------------
>>> +
>>> +Required properties:
>>> + - compatible :
>>> +       "marvell,pxa2xx-lcdc",
>>
>> No differences in h/w for any of the chips?
> All pxa25x, pxa27x and pxa3xx are compatible.
> AFAIK, pxa3xx has an IP with additional registers. But :
>  - these (this) register(s) is not necessary for the display controller to work
>    (it's more a control to shift red/green/blue values, and energy management)
>  - all the registers in pxa2{5,7}x are the same in pxa3xx
>
> The pxafb driver acts today on the subset of registers which are the same across
> all pxaXXX variants. This is what made me think only one compatible property was
> required.
>
> If I'm wrong, I could add "marvell,pxa3xx-lcdc", is that what you think I should
> do ?

I would prefer specific compatibles (e.g. marvell,pxa270-lcdc) in
addition to a generic one. You never know when a specific chip will
have some quirk even though "the IP is the same".

>>
>>> + - reg : Should contain 1 register ranges(address and length).
>>> +        Can contain an additional register range(address and length)
>>> +        for fixed framebuffer memory. Useful for dedicated memories.
>>
>> This is memory that can't be used for anything else? We already have
>> reserved-memory for this if it is just RAM. There's also a binding for
>> on-chip SRAM which should probably be used if the memory is usable for
>> other things.
> That is a wrong copy paste I made. I was more thinking of having only 1 register
> range, and no video memory reservation ...
>
>>> +PXA LCDC Display
>>
>> This should not be specific to PXA, but for this panel. This should be
>> in bindings/display/panel/.
> Sure, for v3.
>
>>> +----------------
>>> +Required properties (as per of_videomode_helper):
>>> + - lcd-type: either "mono-stn", "mono-dstn", "color-stn", "color-dstn",
>>> +                   "color-tft", "smart-panel"
>>> +
>>> +Optional properties (as per of_videomode_helper):
>>> + - power-supply: power supply regulator to the LCD to power it on or off
>>> +                (see regulator.txt)
>>> + - backlight: backlight control (see backlight.txt)
>>> +
>>> +Required nodes:
>>> + - port: connection to the LCD controller
>>> + - display-timings: panel timings (see display-timing.txt)
>>
>> If lcd-type is smart-panel, then this node would not make sense.
> Ah I see, so this could be optional maybe ?

Right.

>
> Actually when I'll move the panel definition to bindings/display/panel, is this
> what I should do :
>  - create a file marvell,pxa2xx-panel
>  - input all these properties into this file

Yes, but the file should be called toshiba,ltm0305a776.txt. It is
irrelevant to the binding that it is pared with pxa2xx. In theory, I
could attach this panel to any SOC.

>
> And then, when a board maintainer will create a devicetree description, he will
> write something like :
>       compatible = "toshiba,ltm0305a776";
>       compatible = "marvell,pxa2xx-panel";

Drop this compatible.

>       lcd-type = "color-tft";
>       ...
>
> If that's the case, I wonder how to "enforce" that a panel used with
> marvell,pxa2xx-lcdc (through the of_graph 'port' node) be compatible with
> marvell,pxa2xx-panel ?

I'm not sure what you mean. Putting the panel into the dts ensures
that. The FB driver may check for toshiba,ltm0305a776 or a list of
panels. However, a DRM driver would probably not check that.

Rob

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Robert Jarzmik]

Rob Herring <robh@kernel.org> writes:

>> The pxafb driver acts today on the subset of registers which are the same across
>> all pxaXXX variants. This is what made me think only one compatible property was
>> required.
>>
>> If I'm wrong, I could add "marvell,pxa3xx-lcdc", is that what you think I should
>> do ?
>
> I would prefer specific compatibles (e.g. marvell,pxa270-lcdc) in
> addition to a generic one. You never know when a specific chip will
> have some quirk even though "the IP is the same".
Okay.

>> And then, when a board maintainer will create a devicetree description, he will
>> write something like :
>>       compatible = "toshiba,ltm0305a776";
>>       compatible = "marvell,pxa2xx-panel";
>
> Drop this compatible.
>
>>       lcd-type = "color-tft";
>>       ...
>>
>> If that's the case, I wonder how to "enforce" that a panel used with
>> marvell,pxa2xx-lcdc (through the of_graph 'port' node) be compatible with
>> marvell,pxa2xx-panel ?
>
> I'm not sure what you mean. Putting the panel into the dts ensures
> that. The FB driver may check for toshiba,ltm0305a776 or a list of
> panels. However, a DRM driver would probably not check that.
>
> Rob
What I mean is that the LDLC controller _must_ be programmmed with the correct
panel type, ie. one register of the LDLC should be set according to this type.

The type is a hardware property of the panel, and yet it is absolutely mandatory
to have it set in the panel.

What I mean is : what is the good way to enforce that this property is set
somewhere in the devicetree description ? Philipp adviced for it to be transfered
to the ldlc description (ie. marvell,pxa2xx-ldlc), while I was thinking of
having it in a panel description.

Cheers.

-- 
Robert

Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding

[Rob Herring]

On Thu, Oct 8, 2015 at 2:15 PM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
> Rob Herring <robh@kernel.org> writes:

>>> And then, when a board maintainer will create a devicetree description, he will
>>> write something like :
>>>       compatible = "toshiba,ltm0305a776";
>>>       compatible = "marvell,pxa2xx-panel";
>>
>> Drop this compatible.
>>
>>>       lcd-type = "color-tft";
>>>       ...
>>>
>>> If that's the case, I wonder how to "enforce" that a panel used with
>>> marvell,pxa2xx-lcdc (through the of_graph 'port' node) be compatible with
>>> marvell,pxa2xx-panel ?
>>
>> I'm not sure what you mean. Putting the panel into the dts ensures
>> that. The FB driver may check for toshiba,ltm0305a776 or a list of
>> panels. However, a DRM driver would probably not check that.
>>
>> Rob
> What I mean is that the LDLC controller _must_ be programmmed with the correct
> panel type, ie. one register of the LDLC should be set according to this type.
>
> The type is a hardware property of the panel, and yet it is absolutely mandatory
> to have it set in the panel.
>
> What I mean is : what is the good way to enforce that this property is set
> somewhere in the devicetree description ? Philipp adviced for it to be transfered
> to the ldlc description (ie. marvell,pxa2xx-ldlc), while I was thinking of
> having it in a panel description.

Either of those options are fine. Neither should need
marvell,pxa2xx-panel though. I'd lean towards putting it in the panel,
but in that case it should be generic for panels which I think it is.
It should probably be optional with not present meaning color-tft
(since every other type is practically dead), but you could say
required on pxa2xx.

The only way to enforce it ATM, is panicking or something if the LCDC
finds it is not set. That's not any worse that checking for
marvell,pxa2xx-panel.

Rob