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Date:   Tue, 15 Mar 2022 21:23:10 +0100
From:   Sam Ravnborg <sam@ravnborg.org>
To:     Christophe Branchereau <cbranchereau@gmail.com>
Cc:     Paul Cercueil <paul@crapouillou.net>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Thierry Reding <thierry.reding@gmail.com>,
        Rob Herring <robh+dt@kernel.org>, linux-kernel@vger.kernel.org,
        linux-mips@vger.kernel.org, dri-devel@lists.freedesktop.org,
        devicetree@vger.kernel.org
Subject: Re: [PATCH v4 2/4] drm/panel: Add panel driver for NewVision NV3052C
 based LCDs
Message-ID: <YjD1rl7jSxLvJhfL@ravnborg.org>
References: <20220311170240.173846-1-cbranchereau@gmail.com>
 <20220311170240.173846-3-cbranchereau@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
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In-Reply-To: <20220311170240.173846-3-cbranchereau@gmail.com>
Precedence: bulk

Hi Christophe,
On Fri, Mar 11, 2022 at 06:02:38PM +0100, Christophe Branchereau wrote:
> This driver supports the NewVision NV3052C based LCDs. Right now, it
> only supports the LeadTek LTK035C5444T 2.4" 640x480 TFT LCD panel, which
> can be found in the Anbernic RG-350M handheld console.

I had to get away from my day-time job and you were the lucky winner.
A couple of comments in the following that you can address now or later.

> 
> Signed-off-by: Christophe Branchereau <cbranchereau@gmail.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> ---
>  drivers/gpu/drm/panel/Kconfig                 |   9 +
>  drivers/gpu/drm/panel/Makefile                |   1 +
>  .../gpu/drm/panel/panel-newvision-nv3052c.c   | 497 ++++++++++++++++++
>  3 files changed, 507 insertions(+)
>  create mode 100644 drivers/gpu/drm/panel/panel-newvision-nv3052c.c
> 
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index bb2e47229c68..40084f709789 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -283,6 +283,15 @@ config DRM_PANEL_NEC_NL8048HL11
>  	  panel (found on the Zoom2/3/3630 SDP boards). To compile this driver
>  	  as a module, choose M here.
>  
> +config DRM_PANEL_NEWVISION_NV3052C
> +	tristate "NewVision NV3052C RGB/SPI panel"
> +	depends on OF && SPI
> +	depends on BACKLIGHT_CLASS_DEVICE
> +	select DRM_MIPI_DBI
> +	help
> +	  Say Y here if you want to enable support for the panels built
> +	  around the NewVision NV3052C display controller.
> +
>  config DRM_PANEL_NOVATEK_NT35510
>  	tristate "Novatek NT35510 RGB panel driver"
>  	depends on OF
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index 5740911f637c..42a7ab54234b 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -26,6 +26,7 @@ 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_NEC_NL8048HL11) += panel-nec-nl8048hl11.o
> +obj-$(CONFIG_DRM_PANEL_NEWVISION_NV3052C) += panel-newvision-nv3052c.o
>  obj-$(CONFIG_DRM_PANEL_NOVATEK_NT35510) += panel-novatek-nt35510.o
>  obj-$(CONFIG_DRM_PANEL_NOVATEK_NT35560) += panel-novatek-nt35560.o
>  obj-$(CONFIG_DRM_PANEL_NOVATEK_NT35950) += panel-novatek-nt35950.o
> diff --git a/drivers/gpu/drm/panel/panel-newvision-nv3052c.c b/drivers/gpu/drm/panel/panel-newvision-nv3052c.c
> new file mode 100644
> index 000000000000..fc31df0dee12
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-newvision-nv3052c.c
> @@ -0,0 +1,497 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * NevVision NV3052C IPS LCD panel driver
> + *
> + * Copyright (C) 2020, Paul Cercueil <paul@crapouillou.net>
> + * Copyright (C) 2022, Christophe Branchereau <cbranchereau@gmail.com>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/media-bus-format.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <video/mipi_display.h>
> +
> +#include <drm/drm_mipi_dbi.h>
> +#include <drm/drm_modes.h>
> +#include <drm/drm_panel.h>
> +
> +struct nv3052c_panel_info {
> +	const struct drm_display_mode *display_modes;
> +	unsigned int num_modes;
> +	u16 width_mm, height_mm;
> +	u32 bus_format, bus_flags;
> +};
> +
> +struct nv3052c {
> +	struct device *dev;
> +	struct drm_panel panel;
> +	struct mipi_dbi dbi;
> +
> +	const struct nv3052c_panel_info *panel_info;
> +
> +	struct regulator *supply;
> +	struct gpio_desc *reset_gpio;
> +};
> +
> +struct nv3052c_reg {
> +	u8 cmd;
> +	u8 val;
> +};
> +
> +static const struct nv3052c_reg nv3052c_panel_regs[] = {
> +	{ 0xff, 0x30 },
> +	{ 0xff, 0x52 },
> +	{ 0xff, 0x01 },
> +	{ 0xe3, 0x00 },
> +	{ 0x40, 0x00 },
> +	{ 0x03, 0x40 },
> +	{ 0x04, 0x00 },
> +	{ 0x05, 0x03 },
> +	{ 0x08, 0x00 },
> +	{ 0x09, 0x07 },
> +	{ 0x0a, 0x01 },
> +	{ 0x0b, 0x32 },
> +	{ 0x0c, 0x32 },
> +	{ 0x0d, 0x0b },
> +	{ 0x0e, 0x00 },
> +	{ 0x23, 0xa0 },
> +
> +	{ 0x24, 0x0c },
> +	{ 0x25, 0x06 },
> +	{ 0x26, 0x14 },
> +	{ 0x27, 0x14 },
> +
> +	{ 0x38, 0xcc },
> +	{ 0x39, 0xd7 },
> +	{ 0x3a, 0x4a },
> +
> +	{ 0x28, 0x40 },
> +	{ 0x29, 0x01 },
> +	{ 0x2a, 0xdf },
> +	{ 0x49, 0x3c },
> +	{ 0x91, 0x77 },
> +	{ 0x92, 0x77 },
> +	{ 0xa0, 0x55 },
> +	{ 0xa1, 0x50 },
> +	{ 0xa4, 0x9c },
> +	{ 0xa7, 0x02 },
> +	{ 0xa8, 0x01 },
> +	{ 0xa9, 0x01 },
> +	{ 0xaa, 0xfc },
> +	{ 0xab, 0x28 },
> +	{ 0xac, 0x06 },
> +	{ 0xad, 0x06 },
> +	{ 0xae, 0x06 },
> +	{ 0xaf, 0x03 },
> +	{ 0xb0, 0x08 },
> +	{ 0xb1, 0x26 },
> +	{ 0xb2, 0x28 },
> +	{ 0xb3, 0x28 },
> +	{ 0xb4, 0x33 },
> +	{ 0xb5, 0x08 },
> +	{ 0xb6, 0x26 },
> +	{ 0xb7, 0x08 },
> +	{ 0xb8, 0x26 },
> +	{ 0xf0, 0x00 },
> +	{ 0xf6, 0xc0 },
> +
> +	{ 0xff, 0x30 },
> +	{ 0xff, 0x52 },
> +	{ 0xff, 0x02 },
> +	{ 0xb0, 0x0b },
> +	{ 0xb1, 0x16 },
> +	{ 0xb2, 0x17 },
> +	{ 0xb3, 0x2c },
> +	{ 0xb4, 0x32 },
> +	{ 0xb5, 0x3b },
> +	{ 0xb6, 0x29 },
> +	{ 0xb7, 0x40 },
> +	{ 0xb8, 0x0d },
> +	{ 0xb9, 0x05 },
> +	{ 0xba, 0x12 },
> +	{ 0xbb, 0x10 },
> +	{ 0xbc, 0x12 },
> +	{ 0xbd, 0x15 },
> +	{ 0xbe, 0x19 },
> +	{ 0xbf, 0x0e },
> +	{ 0xc0, 0x16 },
> +	{ 0xc1, 0x0a },
> +	{ 0xd0, 0x0c },
> +	{ 0xd1, 0x17 },
> +	{ 0xd2, 0x14 },
> +	{ 0xd3, 0x2e },
> +	{ 0xd4, 0x32 },
> +	{ 0xd5, 0x3c },
> +	{ 0xd6, 0x22 },
> +	{ 0xd7, 0x3d },
> +	{ 0xd8, 0x0d },
> +	{ 0xd9, 0x07 },
> +	{ 0xda, 0x13 },
> +	{ 0xdb, 0x13 },
> +	{ 0xdc, 0x11 },
> +	{ 0xdd, 0x15 },
> +	{ 0xde, 0x19 },
> +	{ 0xdf, 0x10 },
> +	{ 0xe0, 0x17 },
> +	{ 0xe1, 0x0a },
> +
> +	{ 0xff, 0x30 },
> +	{ 0xff, 0x52 },
> +	{ 0xff, 0x03 },
> +	{ 0x00, 0x2a },
> +	{ 0x01, 0x2a },
> +	{ 0x02, 0x2a },
> +	{ 0x03, 0x2a },
> +	{ 0x04, 0x61 },
> +	{ 0x05, 0x80 },
> +	{ 0x06, 0xc7 },
> +	{ 0x07, 0x01 },
> +	{ 0x08, 0x03 },
> +	{ 0x09, 0x04 },
> +	{ 0x70, 0x22 },
> +	{ 0x71, 0x80 },
> +	{ 0x30, 0x2a },
> +	{ 0x31, 0x2a },
> +	{ 0x32, 0x2a },
> +	{ 0x33, 0x2a },
> +	{ 0x34, 0x61 },
> +	{ 0x35, 0xc5 },
> +	{ 0x36, 0x80 },
> +	{ 0x37, 0x23 },
> +	{ 0x40, 0x03 },
> +	{ 0x41, 0x04 },
> +	{ 0x42, 0x05 },
> +	{ 0x43, 0x06 },
> +	{ 0x44, 0x11 },
> +	{ 0x45, 0xe8 },
> +	{ 0x46, 0xe9 },
> +	{ 0x47, 0x11 },
> +	{ 0x48, 0xea },
> +	{ 0x49, 0xeb },
> +	{ 0x50, 0x07 },
> +	{ 0x51, 0x08 },
> +	{ 0x52, 0x09 },
> +	{ 0x53, 0x0a },
> +	{ 0x54, 0x11 },
> +	{ 0x55, 0xec },
> +	{ 0x56, 0xed },
> +	{ 0x57, 0x11 },
> +	{ 0x58, 0xef },
> +	{ 0x59, 0xf0 },
> +	{ 0xb1, 0x01 },
> +	{ 0xb4, 0x15 },
> +	{ 0xb5, 0x16 },
> +	{ 0xb6, 0x09 },
> +	{ 0xb7, 0x0f },
> +	{ 0xb8, 0x0d },
> +	{ 0xb9, 0x0b },
> +	{ 0xba, 0x00 },
> +	{ 0xc7, 0x02 },
> +	{ 0xca, 0x17 },
> +	{ 0xcb, 0x18 },
> +	{ 0xcc, 0x0a },
> +	{ 0xcd, 0x10 },
> +	{ 0xce, 0x0e },
> +	{ 0xcf, 0x0c },
> +	{ 0xd0, 0x00 },
> +	{ 0x81, 0x00 },
> +	{ 0x84, 0x15 },
> +	{ 0x85, 0x16 },
> +	{ 0x86, 0x10 },
> +	{ 0x87, 0x0a },
> +	{ 0x88, 0x0c },
> +	{ 0x89, 0x0e },
> +	{ 0x8a, 0x02 },
> +	{ 0x97, 0x00 },
> +	{ 0x9a, 0x17 },
> +	{ 0x9b, 0x18 },
> +	{ 0x9c, 0x0f },
> +	{ 0x9d, 0x09 },
> +	{ 0x9e, 0x0b },
> +	{ 0x9f, 0x0d },
> +	{ 0xa0, 0x01 },
> +
> +	{ 0xff, 0x30 },
> +	{ 0xff, 0x52 },
> +	{ 0xff, 0x02 },
> +	{ 0x01, 0x01 },
> +	{ 0x02, 0xda },
> +	{ 0x03, 0xba },
> +	{ 0x04, 0xa8 },
> +	{ 0x05, 0x9a },
> +	{ 0x06, 0x70 },
> +	{ 0x07, 0xff },
> +	{ 0x08, 0x91 },
> +	{ 0x09, 0x90 },
> +	{ 0x0a, 0xff },
> +	{ 0x0b, 0x8f },
> +	{ 0x0c, 0x60 },
> +	{ 0x0d, 0x58 },
> +	{ 0x0e, 0x48 },
> +	{ 0x0f, 0x38 },
> +	{ 0x10, 0x2b },
> +
> +	{ 0xff, 0x30 },
> +	{ 0xff, 0x52 },
> +	{ 0xff, 0x00 },
> +	{ 0x36, 0x0a },
> +};
There are some random (?) empty lines.
If they have any significance then a short comment would be nice.
If not, then drop the empty lines.

> +
> +static inline struct nv3052c *to_nv3052c(struct drm_panel *panel)
> +{
> +	return container_of(panel, struct nv3052c, panel);
> +}
> +
> +static int nv3052c_prepare(struct drm_panel *panel)
> +{
> +	struct nv3052c *priv = to_nv3052c(panel);
> +	struct mipi_dbi *dbi = &priv->dbi;
> +	unsigned int i;
> +	int err;
> +
> +	err = regulator_enable(priv->supply);
> +	if (err) {
> +		dev_err(priv->dev, "Failed to enable power supply: %d\n", err);
> +		return err;
> +	}
> +
> +	/* Reset the chip */
> +	gpiod_set_value_cansleep(priv->reset_gpio, 1);
> +	usleep_range(10, 1000);
> +	gpiod_set_value_cansleep(priv->reset_gpio, 0);
> +	msleep(5);
> +
> +	for (i = 0; i < ARRAY_SIZE(nv3052c_panel_regs); i++) {
> +		err = mipi_dbi_command(dbi, nv3052c_panel_regs[i].cmd,
> +				       nv3052c_panel_regs[i].val);
> +
> +		if (err) {
> +			dev_err(priv->dev, "Unable to set register: %d\n", err);
> +			goto err_disable_regulator;
> +		}
> +	}
> +
> +	err = mipi_dbi_command(dbi, MIPI_DCS_EXIT_SLEEP_MODE);
> +	if (err) {
> +		dev_err(priv->dev, "Unable to exit sleep mode: %d\n", err);
> +		goto err_disable_regulator;
> +	}
> +
> +	return 0;
> +
> +err_disable_regulator:
> +	regulator_disable(priv->supply);
> +	return err;
> +}
> +
> +static int nv3052c_unprepare(struct drm_panel *panel)
> +{
> +	struct nv3052c *priv = to_nv3052c(panel);
> +	struct mipi_dbi *dbi = &priv->dbi;
> +	int err;
> +
> +	err = mipi_dbi_command(dbi, MIPI_DCS_ENTER_SLEEP_MODE);
> +	if (err) {
> +		dev_err(priv->dev, "Unable to enter sleep mode: %d\n", err);
> +		return err;
Consider to just continue here. In case we fail to enter sleep mode we
will anyway reset the panel and disable the supply voltage.
So things will likely work anyway and we avoid a display with power
where it was supposed to be disabled.
I bet many panels uses the same pattern as this driver, but I think that
continue is the right thing to do here.


> +	}
> +
> +	gpiod_set_value_cansleep(priv->reset_gpio, 1);
> +	regulator_disable(priv->supply);
> +
> +	return 0;
> +}

Everything else looked good - nicely written driver.

	Sam

> +
> +static int nv3052c_enable(struct drm_panel *panel)
> +{
> +	struct nv3052c *priv = to_nv3052c(panel);
> +	struct mipi_dbi *dbi = &priv->dbi;
> +	int err;
> +
> +	err = mipi_dbi_command(dbi, MIPI_DCS_SET_DISPLAY_ON);
> +	if (err) {
> +		dev_err(priv->dev, "Unable to enable display: %d\n", err);
> +		return err;
> +	}
> +
> +	if (panel->backlight) {
> +		/* Wait for the picture to be ready before enabling backlight */
> +		msleep(120);
> +	}
> +
> +	return 0;
> +}
> +
> +static int nv3052c_disable(struct drm_panel *panel)
> +{
> +	struct nv3052c *priv = to_nv3052c(panel);
> +	struct mipi_dbi *dbi = &priv->dbi;
> +	int err;
> +
> +	err = mipi_dbi_command(dbi, MIPI_DCS_SET_DISPLAY_OFF);
> +	if (err) {
> +		dev_err(priv->dev, "Unable to disable display: %d\n", err);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int nv3052c_get_modes(struct drm_panel *panel,
> +			     struct drm_connector *connector)
> +{
> +	struct nv3052c *priv = to_nv3052c(panel);
> +	const struct nv3052c_panel_info *panel_info = priv->panel_info;
> +	struct drm_display_mode *mode;
> +	unsigned int i;
> +
> +	for (i = 0; i < panel_info->num_modes; i++) {
> +		mode = drm_mode_duplicate(connector->dev,
> +					  &panel_info->display_modes[i]);
> +		if (!mode)
> +			return -ENOMEM;
> +
> +		drm_mode_set_name(mode);
> +
> +		mode->type = DRM_MODE_TYPE_DRIVER;
> +		if (panel_info->num_modes == 1)
> +			mode->type |= DRM_MODE_TYPE_PREFERRED;
> +
> +		drm_mode_probed_add(connector, mode);
> +	}
> +
> +	connector->display_info.bpc = 8;
> +	connector->display_info.width_mm = panel_info->width_mm;
> +	connector->display_info.height_mm = panel_info->height_mm;
> +
> +	drm_display_info_set_bus_formats(&connector->display_info,
> +					 &panel_info->bus_format, 1);
> +	connector->display_info.bus_flags = panel_info->bus_flags;
> +
> +	return panel_info->num_modes;
> +}
> +
> +static const struct drm_panel_funcs nv3052c_funcs = {
> +	.prepare	= nv3052c_prepare,
> +	.unprepare	= nv3052c_unprepare,
> +	.enable		= nv3052c_enable,
> +	.disable	= nv3052c_disable,
> +	.get_modes	= nv3052c_get_modes,
> +};
> +
> +static int nv3052c_probe(struct spi_device *spi)
> +{
> +	struct device *dev = &spi->dev;
> +	struct nv3052c *priv;
> +	int err;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->dev = dev;
> +
> +	priv->panel_info = of_device_get_match_data(dev);
> +	if (!priv->panel_info)
> +		return -EINVAL;
> +
> +	priv->supply = devm_regulator_get(dev, "power");
> +	if (IS_ERR(priv->supply))
> +		return dev_err_probe(dev, PTR_ERR(priv->supply), "Failed to get power supply\n");
> +
> +	priv->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(priv->reset_gpio))
> +		return dev_err_probe(dev, PTR_ERR(priv->reset_gpio), "Failed to get reset GPIO\n");
> +
> +	err = mipi_dbi_spi_init(spi, &priv->dbi, NULL);
> +	if (err)
> +		return dev_err_probe(dev, err, "MIPI DBI init failed\n");
> +
> +	priv->dbi.read_commands = NULL;
> +
> +	spi_set_drvdata(spi, priv);
> +
> +	drm_panel_init(&priv->panel, dev, &nv3052c_funcs,
> +		       DRM_MODE_CONNECTOR_DPI);
> +
> +	err = drm_panel_of_backlight(&priv->panel);
> +	if (err)
> +		return dev_err_probe(dev, err, "Failed to attach backlight\n");
> +
> +	drm_panel_add(&priv->panel);
> +
> +	return 0;
> +}
> +
> +static int nv3052c_remove(struct spi_device *spi)
> +{
> +	struct nv3052c *priv = spi_get_drvdata(spi);
> +
> +	drm_panel_remove(&priv->panel);
> +	drm_panel_disable(&priv->panel);
> +	drm_panel_unprepare(&priv->panel);
> +
> +	return 0;
> +}
> +
> +static const struct drm_display_mode ltk035c5444t_modes[] = {
> +	{ /* 60 Hz */
> +		.clock = 24000,
> +		.hdisplay = 640,
> +		.hsync_start = 640 + 96,
> +		.hsync_end = 640 + 96 + 16,
> +		.htotal = 640 + 96 + 16 + 48,
> +		.vdisplay = 480,
> +		.vsync_start = 480 + 5,
> +		.vsync_end = 480 + 5 + 2,
> +		.vtotal = 480 + 5 + 2 + 13,
> +		.flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
> +	},
> +	{ /* 50 Hz */
> +		.clock = 18000,
> +		.hdisplay = 640,
> +		.hsync_start = 640 + 39,
> +		.hsync_end = 640 + 39 + 2,
> +		.htotal = 640 + 39 + 2 + 39,
> +		.vdisplay = 480,
> +		.vsync_start = 480 + 5,
> +		.vsync_end = 480 + 5 + 2,
> +		.vtotal = 480 + 5 + 2 + 13,
> +		.flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
> +	},
> +};
> +
> +static const struct nv3052c_panel_info ltk035c5444t_panel_info = {
> +	.display_modes = ltk035c5444t_modes,
> +	.num_modes = ARRAY_SIZE(ltk035c5444t_modes),
> +	.width_mm = 77,
> +	.height_mm = 64,
> +	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
> +	.bus_flags = DRM_BUS_FLAG_DE_HIGH | DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE,
> +};
> +
> +static const struct of_device_id nv3052c_of_match[] = {
> +	{ .compatible = "leadtek,ltk035c5444t", .data = &ltk035c5444t_panel_info },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, nv3052c_of_match);
> +
> +static struct spi_driver nv3052c_driver = {
> +	.driver = {
> +		.name = "nv3052c",
> +		.of_match_table = nv3052c_of_match,
> +	},
> +	.probe = nv3052c_probe,
> +	.remove = nv3052c_remove,
> +};
> +module_spi_driver(nv3052c_driver);
> +
> +MODULE_AUTHOR("Paul Cercueil <paul@crapouillou.net>");
> +MODULE_AUTHOR("Christophe Branchereau <cbranchereau@gmail.com>");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.35.1