Re: [PATCH 2/2 v3] drm/panel: ws2401: Add driver for WideChips WS2401

[Jagan Teki <jagan@amarulasolutions.com>]

On Thu, Jul 8, 2021 at 5:25 AM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> This adds a driver for panels based on the WideChips WS2401 display
> controller. This display controller is used in the Samsung LMS380KF01
> display found in the Samsung GT-I8160 (Codina) mobile phone and
> possibly others.
>
> As is common with Samsung displays manufacturer commands are necessary
> to configure the display to a working state.
>
> The display optionally supports internal backlight control, but can
> also use an external backlight.
>
> This driver re-uses the DBI infrastructure to communicate with the
> display.
>
> Cc: phone-devel@vger.kernel.org
> Cc: Douglas Anderson <dianders@chromium.org>
> Cc: Noralf Trønnes <noralf@tronnes.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the ws2401_command() macro - we enhanced the
>   mipi_dbi_command() to print errors for everyone instead.
> - Read out MTP properly (used wrong variables)
> - Register internal backlight if and only if the panel->backlight
>   field is NULL after trying to look up external backlight.
> ChangeLog v1->v2:
> - Disable the backlight in ->unprepare() before entering sleep
>   mode.
> - If we are not using internal backlight, close the L2 access
>   after initializing.
> - Depromote some talkative dev_info()s to dev_dbg().
> - Power up and read the MTP values before we register the display.
>   This works fine and is probably how MTP is supposed to work.
> - Fix the set-up of gamma values, this was found in the GT-I8160 HD
>   kernel tree.
> - Bail out properly if drm_panel_of_backlight() returns
>   -EDEFER_PROBE.
> - Drop OF from dependencies since drm_panel_of_backlight() has
>   static inline stubs in the header file.
> - Sort MAINTAINERS properly.
> - Alphabetize includes
> - Use format specifier %#02x so we get 0x... output in debug
> - Drop unnecessary braces around if () in debug macro
> - Drop unused <of.h> include.
> ---
>  MAINTAINERS                                   |   7 +
>  drivers/gpu/drm/panel/Kconfig                 |   9 +
>  drivers/gpu/drm/panel/Makefile                |   1 +
>  .../gpu/drm/panel/panel-widechips-ws2401.c    | 436 ++++++++++++++++++
>  4 files changed, 453 insertions(+)
>  create mode 100644 drivers/gpu/drm/panel/panel-widechips-ws2401.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bd7aff0c120f..10bba4be1678 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5956,6 +5956,13 @@ T:       git git://people.freedesktop.org/~sroland/linux
>  F:     drivers/gpu/drm/vmwgfx/
>  F:     include/uapi/drm/vmwgfx_drm.h
>
> +DRM DRIVER FOR WIDECHIPS WS2401 PANELS
> +M:     Linus Walleij <linus.walleij@linaro.org>
> +S:     Maintained
> +T:     git git://anongit.freedesktop.org/drm/drm-misc
> +F:     Documentation/devicetree/bindings/display/panel/samsung,lms380kf01.yaml
> +F:     drivers/gpu/drm/panel/panel-widechips-ws2401.c
> +
>  DRM DRIVERS
>  M:     David Airlie <airlied@linux.ie>
>  M:     Daniel Vetter <daniel@ffwll.ch>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 4894913936e9..319fa44c4bc9 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -552,6 +552,15 @@ config DRM_PANEL_VISIONOX_RM69299
>           Say Y here if you want to enable support for Visionox
>           RM69299  DSI Video Mode panel.
>
> +config DRM_PANEL_WIDECHIPS_WS2401
> +       tristate "Widechips WS2401 DPI panel driver"
> +       depends on SPI && GPIOLIB
> +       depends on BACKLIGHT_CLASS_DEVICE
> +       select DRM_MIPI_DBI
> +       help
> +         Say Y here if you want to enable support for the Widechips WS2401 DPI
> +         480x800 display controller used in panels such as Samsung LMS380KF01.
> +
>  config DRM_PANEL_XINPENG_XPP055C272
>         tristate "Xinpeng XPP055C272 panel driver"
>         depends on OF
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index cae4d976c069..d94c27df17aa 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -58,4 +58,5 @@ obj-$(CONFIG_DRM_PANEL_TPO_TD043MTEA1) += panel-tpo-td043mtea1.o
>  obj-$(CONFIG_DRM_PANEL_TPO_TPG110) += panel-tpo-tpg110.o
>  obj-$(CONFIG_DRM_PANEL_TRULY_NT35597_WQXGA) += panel-truly-nt35597.o
>  obj-$(CONFIG_DRM_PANEL_VISIONOX_RM69299) += panel-visionox-rm69299.o
> +obj-$(CONFIG_DRM_PANEL_WIDECHIPS_WS2401) += panel-widechips-ws2401.o
>  obj-$(CONFIG_DRM_PANEL_XINPENG_XPP055C272) += panel-xinpeng-xpp055c272.o
> diff --git a/drivers/gpu/drm/panel/panel-widechips-ws2401.c b/drivers/gpu/drm/panel/panel-widechips-ws2401.c
> new file mode 100644
> index 000000000000..95825063f812
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-widechips-ws2401.c
> @@ -0,0 +1,436 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Panel driver for the WideChips WS2401 480x800 DPI RGB panel, used in
> + * the Samsung Mobile Display (SMD) LMS380KF01.
> + * Found in the Samsung Galaxy Ace 2 GT-I8160 mobile phone.
> + * Linus Walleij <linus.walleij@linaro.org>
> + * Inspired by code and know-how in the vendor driver by Gareth Phillips.
> + */
> +#include <drm/drm_mipi_dbi.h>
> +#include <drm/drm_modes.h>
> +#include <drm/drm_panel.h>
> +
> +#include <linux/backlight.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/media-bus-format.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <video/mipi_display.h>
> +
> +#define WS2401_RESCTL                  0xb8 /* Resolution select control */
> +#define WS2401_PSMPS                   0xbd /* SMPS positive control */
> +#define WS2401_NSMPS                   0xbe /* SMPS negative control */
> +#define WS2401_SMPS                    0xbf
> +#define WS2401_BCMODE                  0xc1 /* Backlight control mode */
> +#define WS2401_WRBLCTL                 0xc3 /* Backlight control */
> +#define WS2401_WRDISBV                 0xc4 /* Write manual brightness */
> +#define WS2401_WRCTRLD                 0xc6 /* Write BL control */
> +#define WS2401_WRMIE                   0xc7 /* Write MIE mode */
> +#define WS2401_READ_ID1                        0xda /* Read panel ID 1 */
> +#define WS2401_READ_ID2                        0xdb /* Read panel ID 2 */
> +#define WS2401_READ_ID3                        0xdc /* Read panel ID 3 */
> +#define WS2401_GAMMA_R1                        0xe7 /* Gamma red 1 */
> +#define WS2401_GAMMA_G1                        0xe8 /* Gamma green 1 */
> +#define WS2401_GAMMA_B1                        0xe9 /* Gamma blue 1 */
> +#define WS2401_GAMMA_R2                        0xea /* Gamma red 2 */
> +#define WS2401_GAMMA_G2                        0xeb /* Gamma green 2 */
> +#define WS2401_GAMMA_B2                        0xec /* Gamma blue 2 */
> +#define WS2401_PASSWD1                 0xf0 /* Password command for level 2 */
> +#define WS2401_DISCTL                  0xf2 /* Display control */
> +#define WS2401_PWRCTL                  0xf3 /* Power control */
> +#define WS2401_VCOMCTL                 0xf4 /* VCOM control */
> +#define WS2401_SRCCTL                  0xf5 /* Source control */
> +#define WS2401_PANELCTL                        0xf6 /* Panel control */
> +
> +static const u8 ws2401_dbi_read_commands[] = {
> +       WS2401_READ_ID1,
> +       WS2401_READ_ID2,
> +       WS2401_READ_ID3,
> +       0, /* sentinel */
> +};
> +
> +/**
> + * struct ws2401 - state container for a panel controlled by the WS2401
> + * controller
> + */
> +struct ws2401 {
> +       /** @dev: the container device */
> +       struct device *dev;
> +       /** @dbi: the DBI bus abstraction handle */
> +       struct mipi_dbi dbi;
> +       /** @panel: the DRM panel instance for this device */
> +       struct drm_panel panel;
> +       /** @width: the width of this panel in mm */
> +       u32 width;
> +       /** @height: the height of this panel in mm */
> +       u32 height;
> +       /** @reset: reset GPIO line */
> +       struct gpio_desc *reset;
> +       /** @regulators: VCCIO and VIO supply regulators */
> +       struct regulator_bulk_data regulators[2];
> +       /** @bl: Backlight, if using internal backlight */
> +       struct backlight_device *bl;
> +};
> +
> +static const struct drm_display_mode lms380kf01_480_800_mode = {
> +       /*
> +        * The vendor driver states that the "SMD panel" has a clock
> +        * frequency of 49920000 Hz / 2 = 24960000 Hz.
> +        */
> +       .clock = 24960,
> +       .hdisplay = 480,
> +       .hsync_start = 480 + 8,
> +       .hsync_end = 480 + 8 + 10,
> +       .htotal = 480 + 8 + 10 + 8,
> +       .vdisplay = 800,
> +       .vsync_start = 800 + 8,
> +       .vsync_end = 800 + 8 + 2,
> +       .vtotal = 800 + 8 + 2 + 18,
> +       .width_mm = 50,
> +       .height_mm = 84,
> +       .flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
> +};
> +
> +static inline struct ws2401 *to_ws2401(struct drm_panel *panel)
> +{
> +       return container_of(panel, struct ws2401, panel);
> +}
> +
> +static void ws2401_read_mtp_id(struct ws2401 *ws)
> +{
> +       struct mipi_dbi *dbi = &ws->dbi;
> +       u8 id1, id2, id3;
> +       int ret;
> +
> +       ret = mipi_dbi_command_read(dbi, WS2401_READ_ID1, &id1);
> +       if (ret) {
> +               dev_err(ws->dev, "unable to read MTP ID 1\n");
> +               return;
> +       }
> +       ret = mipi_dbi_command_read(dbi, WS2401_READ_ID2, &id2);
> +       if (ret) {
> +               dev_err(ws->dev, "unable to read MTP ID 2\n");
> +               return;
> +       }
> +       ret = mipi_dbi_command_read(dbi, WS2401_READ_ID3, &id3);
> +       if (ret) {
> +               dev_err(ws->dev, "unable to read MTP ID 3\n");
> +               return;
> +       }
> +       dev_info(ws->dev, "MTP ID: %02x %02x %02x\n", id1, id2, id3);
> +}
> +
> +static int ws2401_power_on(struct ws2401 *ws)
> +{
> +       struct mipi_dbi *dbi = &ws->dbi;
> +       int ret;
> +
> +       /* Power up */
> +       ret = regulator_bulk_enable(ARRAY_SIZE(ws->regulators),
> +                                   ws->regulators);
> +       if (ret) {
> +               dev_err(ws->dev, "failed to enable regulators: %d\n", ret);
> +               return ret;
> +       }
> +       msleep(10);
> +
> +       /* Assert reset >=1 ms */
> +       gpiod_set_value_cansleep(ws->reset, 1);
> +       usleep_range(1000, 5000);
> +       /* De-assert reset */
> +       gpiod_set_value_cansleep(ws->reset, 0);
> +       /* Wait >= 10 ms */
> +       msleep(10);
> +       dev_dbg(ws->dev, "de-asserted RESET\n");

Just a small comment, are these delays are as per init sequence
mentioned in datasheet?

Jagan,