How to select between different display timings? (was: [PATCH 7/8] ARM: dts: tx28: restructure and update DTS file)

How to select between different display timings? (was: [PATCH 7/8] ARM: dts: tx28: restructure and update DTS file)

[Dirk Behme]

Hi Lothar and Shawn,

On 08.08.2013 14:51, Lothar Waßmann wrote:
> - add Copyright header
> - use label references for better readability
> - sort the entries alphabetically
> - add some aliases used by U-Boot to edit the DT data
>
> Signed-off-by: Lothar Waßmann <LW-bxm8fMRDkQLDiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org>
> ---
>   arch/arm/boot/dts/imx28-tx28.dts |  693 +++++++++++++++++++++++++++++++++-----
>   1 files changed, 611 insertions(+), 82 deletions(-)
>
> diff --git a/arch/arm/boot/dts/imx28-tx28.dts b/arch/arm/boot/dts/imx28-tx28.dts
> index 37be532..866af60 100644
> --- a/arch/arm/boot/dts/imx28-tx28.dts
> +++ b/arch/arm/boot/dts/imx28-tx28.dts
...
> +&lcdif {
> +       pinctrl-names = "default";
> +       pinctrl-0 = <&lcdif_24bit_pins_a &lcdif_sync_pins_a &lcdif_ctrl_pins_a>;
> +       lcd-supply = <&reg_lcd>;
> +       display = <&display>;
> +       status = "okay";
> +
> +       display: display@0 {
> +               bits-per-pixel = <32>;
> +               bus-width = <24>;
> +
> +               display-timings {
> +                       native-mode = <&timing5>;
> +                       timing0: timing0 {
> +                               panel-name = "VGA";
> +                               clock-frequency = <25175000>;
> +                               hactive = <640>;
> +                               vactive = <480>;
> +                               hback-porch = <48>;
> +                               hsync-len = <96>;
> +                               hfront-porch = <16>;
> +                               vback-porch = <33>;
> +                               vsync-len = <2>;
> +                               vfront-porch = <10>;
> +                               hsync-active = <0>;
> +                               vsync-active = <0>;
> +                               de-active = <1>;
> +                               pixelclk-active = <1>;
> +                       };
> +
> +                       timing1: timing1 {
> +                               panel-name = "ETV570";
> +                               clock-frequency = <25175000>;
> +                               hactive = <640>;
> +                               vactive = <480>;
> +                               hback-porch = <114>;
> +                               hsync-len = <30>;
> +                               hfront-porch = <16>;
> +                               vback-porch = <32>;
> +                               vsync-len = <3>;
> +                               vfront-porch = <10>;
> +                               hsync-active = <0>;
> +                               vsync-active = <0>;
> +                               de-active = <1>;
> +                               pixelclk-active = <1>;
> +                       };
> +
> +                       timing2: timing2 {
> +                               panel-name = "ET0350";
> +                               clock-frequency = <6500000>;
> +                               hactive = <320>;
> +                               vactive = <240>;
> +                               hback-porch = <34>;
> +                               hsync-len = <34>;
> +                               hfront-porch = <20>;
> +                               vback-porch = <15>;
> +                               vsync-len = <3>;
> +                               vfront-porch = <4>;
> +                               hsync-active = <0>;
> +                               vsync-active = <0>;
> +                               de-active = <1>;
> +                               pixelclk-active = <1>;
> +                       };
> +
> +                       timing3: timing3 {
> +                               panel-name = "ET0430";
> +                               clock-frequency = <9000000>;
> +                               hactive = <480>;
> +                               vactive = <272>;
> +                               hback-porch = <2>;
> +                               hsync-len = <41>;
> +                               hfront-porch = <2>;
> +                               vback-porch = <2>;
> +                               vsync-len = <10>;
> +                               vfront-porch = <2>;
> +                               hsync-active = <0>;
> +                               vsync-active = <0>;
> +                               de-active = <1>;
> +                               pixelclk-active = <1>;
> +                       };
> +
> +                       timing4: timing4 {
> +                               panel-name = "ET0500", "ET0700";
> +                               clock-frequency = <33260000>;
> +                               hactive = <800>;
> +                               vactive = <480>;
> +                               hback-porch = <88>;
> +                               hsync-len = <128>;
> +                               hfront-porch = <40>;
> +                               vback-porch = <33>;
> +                               vsync-len = <2>;
> +                               vfront-porch = <10>;
> +                               hsync-active = <0>;
> +                               vsync-active = <0>;
> +                               de-active = <1>;
> +                               pixelclk-active = <1>;
> +                       };
> +
> +                       timing5: timing5 {
> +                               panel-name = "ETQ570";
> +                               clock-frequency = <6400000>;
> +                               hactive = <320>;
> +                               vactive = <240>;
> +                               hback-porch = <38>;
> +                               hsync-len = <30>;
> +                               hfront-porch = <30>;
> +                               vback-porch = <16>;
> +                               vsync-len = <3>;
> +                               vfront-porch = <4>;
> +                               hsync-active = <0>;
> +                               vsync-active = <0>;
> +                               de-active = <1>;
> +                               pixelclk-active = <1>;
> +                       };
> +               };
> +       };
> +};

Being no graphics expert, looking at above device tree change, I'd like 
to understand how this can be used to switch between different display 
timings?

In the kernel, I've found the code which selects the default/native-mode 
(of_display_timing.c). But, as here, if there is a native/default mode, 
there are alternative modes. I haven't understood how and who to select 
these other modes? In this case, how could the alternative modes 
timing0/1/2/3/4 be selected in the kernel?

Do you have any pointers regarding this?

Many thanks and best regards

Dirk



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Re: How to select between different display timings? (was: [PATCH 7/8] ARM: dts: tx28: restructure and update DTS file)

[Lothar Waßmann]

Hi,

Dirk Behme wrote:
> Hi Lothar and Shawn,
> 
> On 08.08.2013 14:51, Lothar Waßmann wrote:
> > - add Copyright header
> > - use label references for better readability
> > - sort the entries alphabetically
> > - add some aliases used by U-Boot to edit the DT data
> >
> > Signed-off-by: Lothar Waßmann <LW-bxm8fMRDkQLDiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org>
> > ---
> >   arch/arm/boot/dts/imx28-tx28.dts |  693 +++++++++++++++++++++++++++++++++-----
> >   1 files changed, 611 insertions(+), 82 deletions(-)
> >
> > diff --git a/arch/arm/boot/dts/imx28-tx28.dts b/arch/arm/boot/dts/imx28-tx28.dts
> > index 37be532..866af60 100644
> > --- a/arch/arm/boot/dts/imx28-tx28.dts
> > +++ b/arch/arm/boot/dts/imx28-tx28.dts
> ...
> > +&lcdif {
> > +       pinctrl-names = "default";
> > +       pinctrl-0 = <&lcdif_24bit_pins_a &lcdif_sync_pins_a &lcdif_ctrl_pins_a>;
> > +       lcd-supply = <&reg_lcd>;
> > +       display = <&display>;
> > +       status = "okay";
> > +
> > +       display: display@0 {
> > +               bits-per-pixel = <32>;
> > +               bus-width = <24>;
> > +
> > +               display-timings {
> > +                       native-mode = <&timing5>;
                            ^^^^^^^^^^^^^^^^^^^^^^^^^
> > +                       timing0: timing0 {
[...]
> > +                       };
> > +               };
> > +       };
> > +};
> 
> Being no graphics expert, looking at above device tree change, I'd like 
> to understand how this can be used to switch between different display 
> timings?
> 
> In the kernel, I've found the code which selects the default/native-mode 
> (of_display_timing.c). But, as here, if there is a native/default mode, 
> there are alternative modes. I haven't understood how and who to select 
> these other modes? In this case, how could the alternative modes 
> timing0/1/2/3/4 be selected in the kernel?
> 
> Do you have any pointers regarding this?
> 
You need to set the property 'native-mode' to the phandle of the
display-timings entry like marked above.


Lothar Waßmann
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Re: How to select between different display timings?

[Dirk Behme]

Am 14.02.2014 15:02, schrieb Lothar Waßmann:
> Hi,
>
> Dirk Behme wrote:
>> Hi Lothar and Shawn,
>>
>> On 08.08.2013 14:51, Lothar Waßmann wrote:
>>> - add Copyright header
>>> - use label references for better readability
>>> - sort the entries alphabetically
>>> - add some aliases used by U-Boot to edit the DT data
>>>
>>> Signed-off-by: Lothar Waßmann <LW-bxm8fMRDkQLDiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org>
>>> ---
>>>    arch/arm/boot/dts/imx28-tx28.dts |  693 +++++++++++++++++++++++++++++++++-----
>>>    1 files changed, 611 insertions(+), 82 deletions(-)
>>>
>>> diff --git a/arch/arm/boot/dts/imx28-tx28.dts b/arch/arm/boot/dts/imx28-tx28.dts
>>> index 37be532..866af60 100644
>>> --- a/arch/arm/boot/dts/imx28-tx28.dts
>>> +++ b/arch/arm/boot/dts/imx28-tx28.dts
>> ...
>>> +&lcdif {
>>> +       pinctrl-names = "default";
>>> +       pinctrl-0 = <&lcdif_24bit_pins_a &lcdif_sync_pins_a &lcdif_ctrl_pins_a>;
>>> +       lcd-supply = <&reg_lcd>;
>>> +       display = <&display>;
>>> +       status = "okay";
>>> +
>>> +       display: display@0 {
>>> +               bits-per-pixel = <32>;
>>> +               bus-width = <24>;
>>> +
>>> +               display-timings {
>>> +                       native-mode = <&timing5>;
>                              ^^^^^^^^^^^^^^^^^^^^^^^^^
>>> +                       timing0: timing0 {
> [...]
>>> +                       };
>>> +               };
>>> +       };
>>> +};
>>
>> Being no graphics expert, looking at above device tree change, I'd like
>> to understand how this can be used to switch between different display
>> timings?
>>
>> In the kernel, I've found the code which selects the default/native-mode
>> (of_display_timing.c). But, as here, if there is a native/default mode,
>> there are alternative modes. I haven't understood how and who to select
>> these other modes? In this case, how could the alternative modes
>> timing0/1/2/3/4 be selected in the kernel?
>>
>> Do you have any pointers regarding this?
>>
> You need to set the property 'native-mode' to the phandle of the
> display-timings entry like marked above.

Hmm, let's see if we talk about the same thing ;) Let me rephrase my 
questions:

Using above example and booting a system with the resulting .dtb, 
timing5 is selected at boot time, correct?

Assuming I want to use timing1 instead: who would set when the 
property 'native-mode' to &timing1?

Can the switch to

native-mode = <&timing1>;

only be done at compile time of the dts -> dtb? Or can this be done at 
boot/kernel run time, too?

In the end, I'm looking for a way to have several timings like above 
in the device tree, and select one at kernel boot time based on the 
display detected. Would this be possible?

Many thanks and best regards

Dirk


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Re: How to select between different display timings?

[Anatolij Gustschin]

On Fri, 14 Feb 2014 18:35:25 +0100
Dirk Behme <dirk.behme-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
...
> > You need to set the property 'native-mode' to the phandle of the
> > display-timings entry like marked above.
> 
> Hmm, let's see if we talk about the same thing ;) Let me rephrase my 
> questions:
> 
> Using above example and booting a system with the resulting .dtb, 
> timing5 is selected at boot time, correct?

yes.

> Assuming I want to use timing1 instead: who would set when the 
> property 'native-mode' to &timing1?
> 
> Can the switch to
> 
> native-mode = <&timing1>;
> 
> only be done at compile time of the dts -> dtb? Or can this be done at 
> boot/kernel run time, too?

it could be done in U-Boot before booting the kernel. You can load
the dtb and patch the property as needed, i.e.:

U-Boot > tftp 107f0000 ${fdtfile}
U-Boot > fdt addr 107f0000
U-Boot > fdt pri /soc/aips-bus@02000000/ldb@020e0008/lvds-channel@0/display-timings
display-timings {
	native-mode = <0x0000000d>;
	hsd100pxn1 {
		clock-frequency = <0x03dfd240>;
		hactive = <0x00000400>;
		vactive = <0x00000300>;
		hback-porch = <0x000000dc>;
		hfront-porch = <0x00000028>;
		vback-porch = <0x00000015>;
		vfront-porch = <0x00000007>;
		hsync-len = <0x0000003c>;
		vsync-len = <0x0000000a>;
		linux,phandle = <0x0000000d>;
		phandle = <0x0000000d>;
	};
	wvga {
		clock-frequency = <0x019bfcc0>;
		hactive = <0x00000320>;
		vactive = <0x000001e0>;
		hback-porch = <0x00000028>;
		hfront-porch = <0x0000003c>;
		vback-porch = <0x0000000a>;
		vfront-porch = <0x0000000a>;
		hsync-len = <0x00000014>;
		vsync-len = <0x0000000a>;
		hsync-active = <0x00000000>;
		vsync-active = <0x00000000>;
		de-active = <0x00000001>;
		pixelclk-active = <0x00000000>;
		linux,phandle = <0x0000000e>;
		phandle = <0x0000000e>;
	};
};

U-Boot > fdt set /soc/aips-bus@02000000/ldb@020e0008/lvds-channel@0/display-timings native-mode <0x0000000e>

U-Boot > fdt list /soc/aips-bus@02000000/ldb@020e0008/lvds-channel@0/display-timings/          
display-timings {
	native-mode = <0x0000000e>;
	hsd100pxn1 {
	};
	wvga {
	};
};

native-mode is referencing second timing node now.

But note that dtc could eliminate the phandles in the nodes if
these are not referenced in dts. To avoid this, the nodes could
contain a self-reference:

 timing1: wvga {
   ...
   linux,phandle = <&timing1>;
 };

> In the end, I'm looking for a way to have several timings like above 
> in the device tree, and select one at kernel boot time based on the 
> display detected. Would this be possible?

You could add a function in U-Boot to detect the display and
update the dtb before booting. This function can be called
before booting if you define CONFIG_OF_BOARD_SETUP in the
U-Boot config file for your board and provide ft_board_setup()
in your board code.

HTH,

Anatolij
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