[PATCH] drm/panel: simple: Support simple VGA panels

[Michal Vokáč]

On 16.7.2018 11:23, Linus Walleij wrote:
> The need to support some straight-forward VGA panels that are
> not adhering to any standard like DPI arise in the ARM RTSM VE
> Real-Time Systems Model Virtual Executive. This emulator (which
> is not QEMU) does not model any bridge or panel other than
> displaying whatever the user defines that they have.
> 
> Currently a fake "DPI panel" is used for this with the old
> FBDEV driver, but this is wrong as it is not conforming to any
> MIPI DPI standards. However the resolution chosen there is
> standard VGA, and we can cover this with the simple panel
> by simply adding the most common VGA resolutions as a kind
> of "simple panel".
> 
> In difference from other cases where "simple panel" might be
> hiding something more complex (such as a panel driver or bridge)
> this case is actually applicable, since we are running inside
> a simulation with no real hardware on the output.
> 
> Cc: devicetree at vger.kernel.org
> Cc: Sudeep Holla <sudeep.holla at arm.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> Cc: Liviu Dudau <liviu.dudau at arm.com>
> Cc: Robin Murphy <robin.murphy at arm.com>
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
> ---
>   .../display/panel/video-graphics-array.txt    | 21 ++++++
>   drivers/gpu/drm/panel/panel-simple.c          | 66 +++++++++++++++++++
>   2 files changed, 87 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/display/panel/video-graphics-array.txt
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/video-graphics-array.txt b/Documentation/devicetree/bindings/display/panel/video-graphics-array.txt
> new file mode 100644
> index 000000000000..193d24ebe052
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/video-graphics-array.txt
> @@ -0,0 +1,21 @@
> +Video Graphics Array
> +
> +This binding is for simple panels using the standardized VGA resolutions
> +defined by de facto standards beginning with the IBM PS/2 in 1987.
> +
> +Required properties:
> +- compatible: should be "video-graphics-array"
> +
> +This binding is compatible with the simple-panel binding, which is specified
> +in simple-panel.txt in this directory.
> +
> +Example:
> +
> +panel {
> +	compatible = "video-graphics-array";
> +	port {
> +		vga_panel_in: endpoint {
> +			remote-endpoint = <&foo>;
> +		};
> +	};
> +};
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index cbf1ab404ee7..db4db5a3f75e 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -2069,6 +2069,69 @@ static const struct panel_desc winstar_wf35ltiacd = {
>   	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
>   };
>   
> +static const struct drm_display_mode video_graphics_array_modes[] = {
> +	{
> +		/*
> +		 * This is the most standardized "vanilla" VGA mode there is:
> +		 * 640x480 @ 60 Hz
> +		 */
> +		.clock = 27175,
> +		.hdisplay = 640,
> +		.hsync_start = 640 + 16,
> +		.hsync_end = 640 + 16 + 96,
> +		.htotal = 640 + 16 + 96 + 48,
> +		.vdisplay = 480,
> +		.vsync_start = 480 + 10,
> +		.vsync_end = 480 + 10 + 2,
> +		.vtotal = 480 + 10 + 2 + 33,
> +		.vrefresh = 60,
> +		.flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
> +	},
> +	{
> +		/* SVGA 800x600 @60 Hz */
> +		.clock = 40000,
> +		.hdisplay = 800,
> +		.hsync_start = 800 + 40,
> +		.hsync_end = 800 + 40 + 128,
> +		.htotal = 800 + 40 + 128 + 88,
> +		.vdisplay = 600,
> +		.vsync_start = 600 + 1,
> +		.vsync_end = 600 + 1 + 4,
> +		.vtotal = 600 + 1 + 4 + 23,
> +		.vrefresh = 60,
> +		.flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
> +	},
> +	{
> +		/* XGA 1024x768 @60 Hz */
> +		.clock = 65000,
> +		.hdisplay = 1024,
> +		.hsync_start = 1024 + 24,
> +		.hsync_end = 1024 + 24 + 136,
> +		.htotal = 1024 + 24 + 136 + 160,
> +		.vdisplay = 768,
> +		.vsync_start = 768 + 3,
> +		.vsync_end = 768 + 3 + 6,
> +		.vtotal = 768 + 3 + 6 + 29,
> +		.vrefresh = 60,
> +		.flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
> +	},
> +};
> +
> +static const struct panel_desc video_graphics_array = {
> +	.modes = video_graphics_array_modes,
> +	.num_modes = ARRAY_SIZE(video_graphics_array_modes),
> +	.bpc = 8,
> +	/*
> +	 * Some typical 4:3 aspect ratio VGA monitor surely has these dimensions
> +	 * of 40x30 mm.
I am sure it has not :) s/mm/cm or add a zero.

Michal

> +	 */
> +	.size = {
> +		.width = 400,
> +		.height = 300,
> +	},
> +	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
> +};
> +
>   static const struct of_device_id platform_of_match[] = {
>   	{
>   		.compatible = "ampire,am-480272h3tmqw-t01h",
> @@ -2286,6 +2349,9 @@ static const struct of_device_id platform_of_match[] = {
>   	}, {
>   		.compatible = "winstar,wf35ltiacd",
>   		.data = &winstar_wf35ltiacd,
> +	}, {
> +		.compatible = "video-graphics-array",
> +		.data = &video_graphics_array,
>   	}, {
>   		/* sentinel */
>   	}
>