linux-kernel - Re: [PATCH v2 5/5] drm/tiny: panel-mipi-dbi: Support the pixel format property

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Date: Tue, 21 May 2024 10:04:39 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: noralf@...nnes.org, Jessica Zhang <quic_jesszhan@...cinc.com>,
 Sam Ravnborg <sam@...nborg.org>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Kamlesh Gurudasani <kamlesh.gurudasani@...il.com>,
 Tommaso Merciai <tommaso.merciai@...rulasolutions.com>
Subject: Re: [PATCH v2 5/5] drm/tiny: panel-mipi-dbi: Support the pixel format
 property

On 12/05/2024 17:25, Noralf Trønnes via B4 Relay wrote:
> From: Noralf Trønnes <noralf@...nnes.org>
> 
> Add support for these pixel format property values:
> - r5g6b5, RGB565
> - b6x2g6x2r6x2, BGR666
> 
> BGR666 is presented to userspace as RGB888. The 2 LSB in each color
> are discarded by the controller. The pixel is sent on the wire using
> 8 bits per word (little endian) so the controller sees it as BGR.
> 
> RGB565 is the default if the property is not present.
> 
> Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> ---
>   drivers/gpu/drm/tiny/panel-mipi-dbi.c | 55 ++++++++++++++++++++++++++++++++++-
>   1 file changed, 54 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tiny/panel-mipi-dbi.c b/drivers/gpu/drm/tiny/panel-mipi-dbi.c
> index f80a141fcf36..f3aa2abce314 100644
> --- a/drivers/gpu/drm/tiny/panel-mipi-dbi.c
> +++ b/drivers/gpu/drm/tiny/panel-mipi-dbi.c
> @@ -26,6 +26,49 @@
>   
>   #include <video/mipi_display.h>
>   
> +struct panel_mipi_dbi_format {
> +	const char *name;
> +	u32 fourcc;
> +	unsigned int bpp;
> +};
> +
> +static const struct panel_mipi_dbi_format panel_mipi_dbi_formats[] = {
> +	{ "r5g6b5", DRM_FORMAT_RGB565, 16 },
> +	{ "b6x2g6x2r6x2", DRM_FORMAT_RGB888, 24 },
> +};
> +
> +static int panel_mipi_dbi_get_format(struct device *dev, u32 *formats, unsigned int *bpp)
> +{
> +	const char *format_name;
> +	unsigned int i;
> +	int ret;
> +
> +	formats[1] = DRM_FORMAT_XRGB8888;
> +
> +	ret = device_property_read_string(dev, "format", &format_name);
> +	if (ret) {
> +		/* Old Device Trees don't have this property */
> +		formats[0] = DRM_FORMAT_RGB565;
> +		*bpp = 16;
> +		return 0;
> +	}
> +
> +	for (i = 0; i < ARRAY_SIZE(panel_mipi_dbi_formats); i++) {
> +		const struct panel_mipi_dbi_format *format = &panel_mipi_dbi_formats[i];
> +
> +		if (strcmp(format_name, format->name))
> +			continue;
> +
> +		formats[0] = format->fourcc;
> +		*bpp = format->bpp;
> +		return 0;
> +	}
> +
> +	dev_err(dev, "Pixel format is not supported: '%s'\n", format_name);
> +
> +	return -EINVAL;
> +}
> +
>   static const u8 panel_mipi_dbi_magic[15] = { 'M', 'I', 'P', 'I', ' ', 'D', 'B', 'I',
>   					     0, 0, 0, 0, 0, 0, 0 };
>   
> @@ -276,6 +319,9 @@ static int panel_mipi_dbi_spi_probe(struct spi_device *spi)
>   	struct drm_device *drm;
>   	struct mipi_dbi *dbi;
>   	struct gpio_desc *dc;
> +	unsigned int bpp;
> +	size_t buf_size;
> +	u32 formats[2];
>   	int ret;
>   
>   	dbidev = devm_drm_dev_alloc(dev, &panel_mipi_dbi_driver, struct mipi_dbi_dev, drm);
> @@ -323,7 +369,14 @@ static int panel_mipi_dbi_spi_probe(struct spi_device *spi)
>   	if (IS_ERR(dbidev->driver_private))
>   		return PTR_ERR(dbidev->driver_private);
>   
> -	ret = mipi_dbi_dev_init(dbidev, &panel_mipi_dbi_pipe_funcs, &mode, 0);
> +	ret = panel_mipi_dbi_get_format(dev, formats, &bpp);
> +	if (ret)
> +		return ret;
> +
> +	buf_size = DIV_ROUND_UP(mode.hdisplay * mode.vdisplay * bpp, 8);
> +	ret = mipi_dbi_dev_init_with_formats(dbidev, &panel_mipi_dbi_pipe_funcs,
> +					     formats, ARRAY_SIZE(formats),
> +					     &mode, 0, buf_size);
>   	if (ret)
>   		return ret;
>   
> 

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>