Re: [PATCH 2/4] drm/panel: Add driver for Novatek NT37705 panel

["Luca Weiss" <luca.weiss@fairphone.com>]

On Fri May 8, 2026 at 10:06 AM CEST, Thomas Zimmermann wrote:
> Hi
>
> Am 01.05.26 um 15:52 schrieb Luca Weiss:
>> Add support for the 2484x1116 AMOLED panel from BOE (BJ631JHM-T71-D900)
>> bundled with a NT37705 driver IC, as found on the Fairphone (Gen. 6)
>> smartphone.
>>
>> The panel can also be configured in 10-bit (RGB101010) mode, however
>> currently it's configured in 8-bit (RGB888) since there's some issues in
>> the Qualcomm DPU driver when driving this panel in 10-bit.
>>
>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
>> ---
>>   drivers/gpu/drm/panel/Kconfig                 |  11 +
>>   drivers/gpu/drm/panel/Makefile                |   1 +
>>   drivers/gpu/drm/panel/panel-novatek-nt37705.c | 413 ++++++++++++++++++++++++++
>>   3 files changed, 425 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
>> index 979109c27b9b..59ab3f29d8ef 100644
>> --- a/drivers/gpu/drm/panel/Kconfig
>> +++ b/drivers/gpu/drm/panel/Kconfig
>> @@ -624,6 +624,17 @@ config DRM_PANEL_NOVATEK_NT37700F
>>   	  Say Y here if you want to enable support for Novatek NT37700F DSI
>>   	  panel module. The panel has a resolution of 1080x2160.
>>   
>> +config DRM_PANEL_NOVATEK_NT37705
>> +	tristate "Novatek NT37705-based DSI panel"
>> +	depends on OF
>> +	depends on DRM_MIPI_DSI
>> +	depends on BACKLIGHT_CLASS_DEVICE
>> +	select DRM_KMS_HELPER
>> +	help
>> +	  Say Y here if you want to enable support for Novatek NT37705-based
>> +	  display panels, such as the one found in the The Fairphone (Gen. 6)
>
> Duplicate 'the'

Marketing really wanted to have it be "The Fairphone". Will change and
make it saner.

>
>> +	  smartphone.
>> +
>>   config DRM_PANEL_NOVATEK_NT37801
>>   	tristate "Novatek NT37801/NT37810 AMOLED DSI panel"
>>   	depends on OF
>> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
>> index 0d694acbfbb6..94639bc58ca8 100644
>> --- a/drivers/gpu/drm/panel/Makefile
>> +++ b/drivers/gpu/drm/panel/Makefile
>> @@ -61,6 +61,7 @@ obj-$(CONFIG_DRM_PANEL_NOVATEK_NT36523) += panel-novatek-nt36523.o
>>   obj-$(CONFIG_DRM_PANEL_NOVATEK_NT36672A) += panel-novatek-nt36672a.o
>>   obj-$(CONFIG_DRM_PANEL_NOVATEK_NT36672E) += panel-novatek-nt36672e.o
>>   obj-$(CONFIG_DRM_PANEL_NOVATEK_NT37700F) += panel-novatek-nt37700f.o
>> +obj-$(CONFIG_DRM_PANEL_NOVATEK_NT37705) += panel-novatek-nt37705.o
>>   obj-$(CONFIG_DRM_PANEL_NOVATEK_NT37801) += panel-novatek-nt37801.o
>>   obj-$(CONFIG_DRM_PANEL_NOVATEK_NT39016) += panel-novatek-nt39016.o
>>   obj-$(CONFIG_DRM_PANEL_MANTIX_MLAF057WE51) += panel-mantix-mlaf057we51.o
>> diff --git a/drivers/gpu/drm/panel/panel-novatek-nt37705.c b/drivers/gpu/drm/panel/panel-novatek-nt37705.c
>> new file mode 100644
>> index 000000000000..27bd8072ccd1
>> --- /dev/null
>> +++ b/drivers/gpu/drm/panel/panel-novatek-nt37705.c
>> @@ -0,0 +1,413 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Generated with linux-mdss-dsi-panel-driver-generator from vendor device tree.
>> + * Copyright (c) 2026 Luca Weiss <luca.weiss@fairphone.com>
>> + */
>> +
>> +#include <linux/backlight.h>
>> +#include <linux/delay.h>
>> +#include <linux/gpio/consumer.h>
>> +#include <linux/mod_devicetable.h>
>> +#include <linux/module.h>
>> +#include <linux/regulator/consumer.h>
>> +
>> +#include <video/mipi_display.h>
>> +
>> +#include <drm/display/drm_dsc.h>
>> +#include <drm/display/drm_dsc_helper.h>
>
> IIRC this requires
>
>   select DRM_DISPLAY_DSC_HELPER
>
> in the Kconfig. Maybe double-check.

Will check. Always difficult to figure out the proper dependencies in a
fully-featured defconfig build.

>
>> +#include <drm/drm_mipi_dsi.h>
>> +#include <drm/drm_modes.h>
>> +#include <drm/drm_panel.h>
>> +#include <drm/drm_probe_helper.h>
>> +
>> +struct nt37705_panel {
>> +	struct drm_panel panel;
>> +	struct mipi_dsi_device *dsi;
>> +	struct drm_dsc_config dsc;
>> +	struct regulator_bulk_data *supplies;
>> +	struct gpio_desc *reset_gpio;
>> +};
>> +
>> +static const struct regulator_bulk_data nt37705_supplies[] = {
>> +	{ .supply = "vddio" },
>> +	{ .supply = "dvdd" },
>> +	{ .supply = "vci" },
>> +};
>> +
>> +static inline struct nt37705_panel *to_nt37705_panel(struct drm_panel *panel)
>> +{
>> +	return container_of_const(panel, struct nt37705_panel, panel);
>
> Either just use container_of or build something that respects the 
> input's const-ness.

I really don't get what you mean here? Why is container_of_const() bad
here?

>
>> +}
>> +
>> +static void nt37705_reset(struct nt37705_panel *ctx)
>> +{
>> +	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
>> +	usleep_range(10000, 11000);
>> +	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
>> +	usleep_range(5000, 6000);
>> +	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
>> +	usleep_range(10000, 11000);
>> +}
>> +
>> +static int nt37705_on(struct nt37705_panel *ctx)
>> +{
>> +	struct mipi_dsi_multi_context dsi_ctx = { .dsi = ctx->dsi };
>> +
>> +	ctx->dsi->mode_flags |= MIPI_DSI_MODE_LPM;
>> +
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0,
>> +				     0x55, 0xaa, 0x52, 0x08, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x1b);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba, 0x18);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x1c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00,
>> +				     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
>> +				     0x00, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x2c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x00, 0x01, 0x01, 0x01, 0x00, 0x05, 0x05,
>> +				     0x05, 0x00, 0x05, 0x05, 0x05, 0x00, 0x00,
>> +				     0x00, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x3c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x0b,
>> +				     0x0b, 0x00, 0x00, 0x0b, 0x0b, 0x00, 0x00,
>> +				     0x00, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x4c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
>> +				     0x1d, 0x00, 0x00, 0x00, 0x1d, 0x00, 0x00,
>> +				     0x00, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x5c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
>> +				     0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
>> +				     0x01, 0x01);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x6c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x0b,
>> +				     0x77, 0x77, 0x00, 0x00, 0x0b, 0x00, 0x1d,
>> +				     0x00, 0x1d);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x7c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x0b,
>> +				     0x77, 0x77, 0x00, 0x00, 0x0b, 0x00, 0x1d,
>> +				     0x00, 0x1d);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x8c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
>> +				     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
>> +				     0x00, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x9c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x11, 0x11, 0x20, 0x02, 0x00, 0x03, 0x00,
>> +				     0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0xa4);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba, 0x00, 0xc0, 0x40, 0x08);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0xa8);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22,
>> +				     0x22);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0xb0);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xba,
>> +				     0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22,
>> +				     0x22);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0,
>> +				     0x55, 0xaa, 0x52, 0x08, 0x01);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x05);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc5, 0x15, 0x15, 0x15, 0xdd);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0,
>> +				     0x55, 0xaa, 0x52, 0x08, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x0e);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb5, 0x32);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0,
>> +				     0x55, 0xaa, 0x52, 0x00, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xff, 0xaa, 0x55, 0xa5, 0x80);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x19);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf2, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x1a);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf4, 0x55);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x11);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf8, 0x01, 0x7f);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x2d);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf8, 0x01, 0x20);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xff, 0xaa, 0x55, 0xa5, 0x81);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x05);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfe, 0x3c);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x02);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf9, 0x04);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x1e);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfb, 0x0f);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x0f);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf5, 0x20);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x0d);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfb, 0x80);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xff, 0xaa, 0x55, 0xa5, 0x83);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x12);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfe, 0x41);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x13);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfd, 0x21);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xff, 0xaa, 0x55, 0xa5, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x35);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, MIPI_DCS_WRITE_CONTROL_DISPLAY,
>> +				     0x20);
>> +	mipi_dsi_dcs_set_column_address_multi(&dsi_ctx, 0x0000, 0x045b);
>> +	mipi_dsi_dcs_set_page_address_multi(&dsi_ctx, 0x0000, 0x09b3);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, MIPI_DCS_SET_GAMMA_CURVE, 0x00);
>> +	mipi_dsi_dcs_set_display_brightness_multi(&dsi_ctx, 0xbb0d);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6f, 0x04);
>> +	mipi_dsi_dcs_set_display_brightness_multi(&dsi_ctx, 0xfe0f);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x81, 0x01, 0x19);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x03, 0x01);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x90, 0x03, 0x03);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x91,
>> +				     0x89, 0x28, 0x00, 0x0c, 0xd2, 0x00, 0x02,
>> +				     0x2f, 0x01, 0x18, 0x00, 0x07, 0x09, 0x75,
>> +				     0x08, 0x34, 0x10, 0xf0);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x2f, 0x02);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x5a, 0x01);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x2f, 0x30);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x6d, 0x00);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x11, 0x00);
>> +	mipi_dsi_msleep(&dsi_ctx, 120);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x29, 0x00);
>> +	mipi_dsi_msleep(&dsi_ctx, 22);
>> +
>> +	return dsi_ctx.accum_err;
>> +}
>> +
>> +static int nt37705_off(struct nt37705_panel *ctx)
>> +{
>> +	struct mipi_dsi_multi_context dsi_ctx = { .dsi = ctx->dsi };
>> +
>> +	ctx->dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
>> +
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x28, 0x00);
>> +	mipi_dsi_msleep(&dsi_ctx, 20);
>> +	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x10, 0x00);
>> +	mipi_dsi_msleep(&dsi_ctx, 120);
>> +
>> +	return dsi_ctx.accum_err;
>> +}
>> +
>> +static int nt37705_prepare(struct drm_panel *panel)
>> +{
>> +	struct nt37705_panel *ctx = to_nt37705_panel(panel);
>> +	struct device *dev = &ctx->dsi->dev;
>> +	struct drm_dsc_picture_parameter_set pps;
>> +	int ret;
>> +
>> +	ret = regulator_bulk_enable(ARRAY_SIZE(nt37705_supplies), ctx->supplies);
>> +	if (ret < 0) {
>
> Common style is to check for errors with
>
>    if (ret)
>
> Here and everywhere else.

At least for regulator_bulk_enable() "ret < 0" is actually more popular
than just "ret".

Kernel doc says "Return: 0 on success or a negative error number on
failure." so a positive integer should in theory never happen so they're
equivalent.

(git grep -h -A2 regulator_bulk_enable | grep if | sed 's|^[ \t]\+||' | sed 's| {$||' | sort | uniq -c)

Thanks for the review!

Regards
Luca