Re: [PATCH v2 3/3] drm/panel: Add MIPI DBI compatible SPI driver

[Maxime Ripard <maxime@cerno.tech>]

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On Tue, Jan 25, 2022 at 06:57:00PM +0100, Noralf Trønnes wrote:
> Add a driver that will work with most MIPI DBI compatible SPI panels.
> This avoids adding a driver for every new MIPI DBI compatible controller
> that is to be used by Linux. The 'compatible' Device Tree property with
> a '.bin' suffix will be used to load a firmware file that contains the
> controller configuration.
> 
> Example (driver will load sainsmart18.bin):
> 
> display@0 {
> 	compatible = "sainsmart18", "panel-mipi-dbi-spi";
> 	reg = <0>;
> 	reset-gpios = <&gpio 25 0>;
> 	dc-gpios = <&gpio 24 0>;
> };
> 
> v2:
> - Drop model property and use compatible instead (Rob)
> - Add wiki entry in MAINTAINERS
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
>  MAINTAINERS                            |   8 +
>  drivers/gpu/drm/panel/Kconfig          |  11 +
>  drivers/gpu/drm/panel/Makefile         |   1 +
>  drivers/gpu/drm/panel/panel-mipi-dbi.c | 394 +++++++++++++++++++++++++
>  4 files changed, 414 insertions(+)
>  create mode 100644 drivers/gpu/drm/panel/panel-mipi-dbi.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d03ad8da1f36..8baa98723bdc 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6047,6 +6047,14 @@ T:	git git://anongit.freedesktop.org/drm/drm-misc
>  F:	Documentation/devicetree/bindings/display/multi-inno,mi0283qt.txt
>  F:	drivers/gpu/drm/tiny/mi0283qt.c
>  
> +DRM DRIVER FOR MIPI DBI compatible panels
> +M:	Noralf Trønnes <noralf@tronnes.org>
> +S:	Maintained
> +W:	https://github.com/notro/panel-mipi-dbi/wiki
> +T:	git git://anongit.freedesktop.org/drm/drm-misc
> +F:	Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
> +F:	drivers/gpu/drm/panel/panel-mipi-dbi.c
> +
>  DRM DRIVER FOR MSM ADRENO GPU
>  M:	Rob Clark <robdclark@gmail.com>
>  M:	Sean Paul <sean@poorly.run>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 434c2861bb40..1851cda5f877 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -274,6 +274,17 @@ config DRM_PANEL_LG_LG4573
>  	  Say Y here if you want to enable support for LG4573 RGB panel.
>  	  To compile this driver as a module, choose M here.
>  
> +config DRM_PANEL_MIPI_DBI
> +	tristate "MIPI DBI compatible panel"
> +	depends on SPI
> +	depends on BACKLIGHT_CLASS_DEVICE
> +	depends on DRM_KMS_HELPER
> +	select DRM_KMS_CMA_HELPER
> +	select DRM_MIPI_DBI
> +	help
> +	  Say Y here if you want to enable support for MIPI DBI compatible panels.
> +	  To compile this driver as a module, choose M here.
> +
>  config DRM_PANEL_NEC_NL8048HL11
>  	tristate "NEC NL8048HL11 RGB panel"
>  	depends on GPIOLIB && OF && SPI
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index d99fbbce49d1..a90c30459964 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -25,6 +25,7 @@ obj-$(CONFIG_DRM_PANEL_LEADTEK_LTK050H3146W) += panel-leadtek-ltk050h3146w.o
>  obj-$(CONFIG_DRM_PANEL_LEADTEK_LTK500HD1829) += panel-leadtek-ltk500hd1829.o
>  obj-$(CONFIG_DRM_PANEL_LG_LB035Q02) += panel-lg-lb035q02.o
>  obj-$(CONFIG_DRM_PANEL_LG_LG4573) += panel-lg-lg4573.o
> +obj-$(CONFIG_DRM_PANEL_MIPI_DBI) += panel-mipi-dbi.o
>  obj-$(CONFIG_DRM_PANEL_NEC_NL8048HL11) += panel-nec-nl8048hl11.o
>  obj-$(CONFIG_DRM_PANEL_NOVATEK_NT35510) += panel-novatek-nt35510.o
>  obj-$(CONFIG_DRM_PANEL_NOVATEK_NT35950) += panel-novatek-nt35950.o
> diff --git a/drivers/gpu/drm/panel/panel-mipi-dbi.c b/drivers/gpu/drm/panel/panel-mipi-dbi.c
> new file mode 100644
> index 000000000000..6e3dc2de21d2
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-mipi-dbi.c
> @@ -0,0 +1,394 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * DRM driver for MIPI DBI compatible display panels
> + *
> + * Copyright 2022 Noralf Trønnes
> + */
> +
> +#include <linux/backlight.h>
> +#include <linux/delay.h>
> +#include <linux/firmware.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/property.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_drv.h>
> +#include <drm/drm_fb_helper.h>
> +#include <drm/drm_gem_atomic_helper.h>
> +#include <drm/drm_gem_cma_helper.h>
> +#include <drm/drm_managed.h>
> +#include <drm/drm_mipi_dbi.h>
> +#include <drm/drm_modeset_helper.h>
> +#include <video/mipi_display.h>
> +
> +static const u8 panel_mipi_dbi_magic[15] = { 'M', 'I', 'P', 'I', ' ', 'D', 'B', 'I',
> +					     0, 0, 0, 0, 0, 0, 0 };
> +
> +/*
> + * The display panel configuration is stored in a firmware file. The Device Tree 'compatible'
> + * property value with a '.bin' suffix is passed to request_firmware() to fetch this file.
> + */
> +struct panel_mipi_dbi_config {
> +	/* Magic string: panel_mipi_dbi_magic */
> +	u8 magic[15];
> +
> +	/* Config file format version */
> +	u8 file_format_version;
> +
> +	/* Width in pixels */
> +	__be16 width;
> +	/* Height in pixels */
> +	__be16 height;
> +
> +	/* Width in millimeters (optional) */
> +	__be16 width_mm;
> +	/* Height in millimeters (optional) */
> +	__be16 height_mm;
> +
> +	/* X-axis panel offset */
> +	__be16 x_offset;
> +	/* Y-axis panel offset */
> +	__be16 y_offset;
> +
> +	/* 4 pad bytes, must be zero */
> +	u8 pad[4];
> +
> +	/*
> +	 * Optional MIPI commands to execute when the display pipeline is enabled.
> +	 * This can be used to configure the display controller.
> +	 *
> +	 * The commands are stored in a byte array with the format:
> +	 *     command, num_parameters, [ parameter, ...], command, ...
> +	 *
> +	 * Some commands require a pause before the next command can be received.
> +	 * Inserting a delay in the command sequence is done by using the NOP command with one
> +	 * parameter: delay in miliseconds (the No Operation command is part of the MIPI Display
> +	 * Command Set where it has no parameters).
> +	 *
> +	 * Example:
> +	 *     command 0x11
> +	 *     sleep 120ms
> +	 *     command 0xb1 parameters 0x01, 0x2c, 0x2d
> +	 *     command 0x29
> +	 *
> +	 * Byte sequence:
> +	 *     0x11 0x00
> +	 *     0x00 0x01 0x78
> +	 *     0xb1 0x03 0x01 0x2c 0x2d
> +	 *     0x29 0x00
> +	 */
> +	u8 commands[];
> +};

I'm not really a fan of parsing raw data in the kernel. I guess we can't
really avoid the introduction of a special case to sleep, but we already
have dt properties for all of the other properties (but X and Y offset,
maybe?)

Maybe we should use those instead?

Maxime

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