Date:   Fri, 22 Dec 2017 12:23:07 -0500
From:   "Jingoo Han" <jingoohan1@...il.com>
To:     "'Felix Brack'" <fb@...c.ch>, <linux-fbdev@...r.kernel.org>
Cc:     <lee.jones@...aro.org>, <daniel.thompson@...aro.org>,
        <b.zolnierkie@...sung.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] backlight: otm3225a: add support for ORISE OTM3225A LCD SoC

On Wednesday, December 20, 2017 12:58 PM, Felix Brack wrote:
> 
> This patch adds a LCD driver supporting the OTM3225A LCD SoC
> from ORISE Technology. This device can drive TFT LC panels having a
> resolution of 240x320 pixels. After initializing the OTM3225A using
> it's SPI interface it switches to use 16-bib RGB as external
> display interface.
> 
> Signed-off-by: Felix Brack <fb@...c.ch>
> ---
>  drivers/video/backlight/Kconfig    |   7 ++
>  drivers/video/backlight/Makefile   |   1 +
>  drivers/video/backlight/otm3225a.c | 210
> +++++++++++++++++++++++++++++++++++++
>  3 files changed, 218 insertions(+)
>  create mode 100644 drivers/video/backlight/otm3225a.c
> 
> diff --git a/drivers/video/backlight/Kconfig
> b/drivers/video/backlight/Kconfig
> index 4e1d2ad..06e187b 100644
> --- a/drivers/video/backlight/Kconfig
> +++ b/drivers/video/backlight/Kconfig
> @@ -150,6 +150,13 @@ config LCD_HX8357
>  	  If you have a HX-8357 LCD panel, say Y to enable its LCD control
>  	  driver.
> 
> +  config LCD_OTM3225A
> +  	tristate "ORISE Technology OTM3225A support"
> +  	depends on SPI
> +  	help
> +  	  If you have a panel based on the OTM3225A controller
> +  	  chip then say y to include a driver for it.
> +
>  endif # LCD_CLASS_DEVICE
> 
>  #
> diff --git a/drivers/video/backlight/Makefile
> b/drivers/video/backlight/Makefile
> index 8905129..b177b91 100644
> --- a/drivers/video/backlight/Makefile
> +++ b/drivers/video/backlight/Makefile
> @@ -17,6 +17,7 @@ obj-$(CONFIG_LCD_S6E63M0)		+= s6e63m0.o
>  obj-$(CONFIG_LCD_TDO24M)		+= tdo24m.o
>  obj-$(CONFIG_LCD_TOSA)			+= tosa_lcd.o
>  obj-$(CONFIG_LCD_VGG2432A4)		+= vgg2432a4.o
> +obj-$(CONFIG_LCD_OTM3225A)		+= otm3225a.o

All entries of Kconfig was alphasorted 4 years ago for reducing
patch collisions. So please add it in alphabetical order as below.

@@ -13,6 +13,7 @@ obj-$(CONFIG_LCD_LD9040)              += ld9040.o
 obj-$(CONFIG_LCD_LMS283GF05)           += lms283gf05.o
 obj-$(CONFIG_LCD_LMS501KF03)           += lms501kf03.o
 obj-$(CONFIG_LCD_LTV350QV)             += ltv350qv.o
+obj-$(CONFIG_LCD_OTM3225A)             += otm3225a.o
 obj-$(CONFIG_LCD_PLATFORM)             += platform_lcd.o


> 
>  obj-$(CONFIG_BACKLIGHT_88PM860X)	+= 88pm860x_bl.o
>  obj-$(CONFIG_BACKLIGHT_AAT2870)		+= aat2870_bl.o
> diff --git a/drivers/video/backlight/otm3225a.c
> b/drivers/video/backlight/otm3225a.c
> new file mode 100644
> index 0000000..0de75f8
> --- /dev/null
> +++ b/drivers/video/backlight/otm3225a.c
> @@ -0,0 +1,210 @@
> +/*
> + * Driver for ORISE Technology OTM3225A SOC for TFT LCD
> + *
> + * Copyright (C) 2014-2017, EETS GmbH, Felix Brack <fb@...c.ch>

Please change the year of copyright as below.

+ * Copyright (C) 2017, EETS GmbH, Felix Brack <fb@...c.ch>

> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> +
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> +
> + * This driver implements a lcd device for the ORISE OTM3225A display
> + * controller. The control interface to the display is SPI and the
> display's
> + * memory is updated over the 16-bit RGB interface.
> + * The main source of information for writing this driver was provided by
> the
> + * OTM3225A datasheet from ORISE Technology. Some information arise from
> the
> + * ILI9328 datasheet from ILITEK as well as from the datasheets and
> sample code
> + * provided by Crystalfontz America Inc. who sells the CFAF240320A-032T,
> a 3.2"
> + * TFT LC display using the OTM3225A controller.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/delay.h>
> +#include <linux/lcd.h>
> +#include <linux/spi/spi.h>

So please add these headers in alphabetical order
for readability.

> +
> +#define OTM3225A_INDEX_REG	0x70
> +#define OTM3225A_DATA_REG	0x72
> +
> +struct otm3225a_data {
> +	struct spi_device *spi;
> +	struct lcd_device *ld;
> +	int power;
> +};
> +
> +struct otm3225a_spi_instruction {
> +	unsigned char reg;	/* register to write */
> +	unsigned short value;	/* data to write to 'reg' */
> +	unsigned short delay;	/* delay in ms after write */
> +};
> +
> +static struct otm3225a_spi_instruction display_init[] = {
> +	{ 0x01, 0x0000, 0 }, { 0x02, 0x0700, 0 }, { 0x03, 0x50A0, 0 },
> +	{ 0x04, 0x0000, 0 }, { 0x08, 0x0606, 0 }, { 0x09, 0x0000, 0 },
> +	{ 0x0A, 0x0000, 0 }, { 0x0C, 0x0000, 0 }, { 0x0D, 0x0000, 0 },
> +	{ 0x0F, 0x0002, 0 }, { 0x11, 0x0007, 0 }, { 0x12, 0x0000, 0 },
> +	{ 0x13, 0x0000, 200 }, { 0x07, 0x0101, 0 }, { 0x10, 0x12B0, 0 },
> +	{ 0x11, 0x0007, 0 }, { 0x12, 0x01BB, 50 }, { 0xB1, 0x0000, 0 },
> +	{ 0xB3, 0x0000, 0 }, { 0xB5, 0x0000, 0 }, { 0xBE, 0x0000, 0 },
> +	{ 0x13, 0x0013, 0 }, { 0x29, 0x0010, 50 }, { 0x30, 0x000A, 0 },
> +	{ 0x31, 0x1326, 0 }, { 0x32, 0x0A29, 0 }, { 0x35, 0x0A0A, 0 },
> +	{ 0x36, 0x1E03, 0 }, { 0x37, 0x031E, 0 }, { 0x38, 0x0706, 0 },
> +	{ 0x39, 0x0303, 0 }, { 0x3C, 0x010E, 0 }, { 0x3D, 0x040E, 0 },
> +	{ 0x50, 0x0000, 0 }, { 0x51, 0x00EF, 0 }, { 0x52, 0x0000, 0 },
> +	{ 0x53, 0x013F, 0 }, { 0x60, 0x2700, 0 }, { 0x61, 0x0001, 0 },
> +	{ 0x6A, 0x0000, 0 }, { 0x80, 0x0000, 0 }, { 0x81, 0x0000, 0 },
> +	{ 0x82, 0x0000, 0 }, { 0x83, 0x0000, 0 }, { 0x84, 0x0000, 0 },
> +	{ 0x85, 0x0000, 0 }, { 0x90, 0x0010, 0 }, { 0x92, 0x0000, 0 },
> +	{ 0x93, 0x0103, 0 }, { 0x95, 0x0210, 0 }, { 0x97, 0x0000, 0 },
> +	{ 0x98, 0x0000, 0 }, { 0x07, 0x0133, 0 },
> +};
> +
> +static struct otm3225a_spi_instruction display_enable_rgb_interface[] = {
> +	{ 0x03, 0x1080, 0 },
> +	{ 0x20, 0x0000, 0 },
> +	{ 0x21, 0x0000, 0 },
> +	{ 0x0C, 0x0111, 500 },
> +};
> +
> +static struct otm3225a_spi_instruction display_off[] = {
> +	{ 0x07, 0x0131, 100 },
> +	{ 0x07, 0x0130, 100 },
> +	{ 0x07, 0x0100, 0 },
> +	{ 0x10, 0x0280, 0 },
> +	{ 0x12, 0x018B, 0 },
> +};
> +
> +static struct otm3225a_spi_instruction display_on[] = {
> +	{ 0x10, 0x1280, 0 },
> +	{ 0x07, 0x0101, 100 },
> +	{ 0x07, 0x0121, 0 },
> +	{ 0x07, 0x0123, 100 },
> +	{ 0x07, 0x0133, 10 },
> +};

Please change these hardcoded values into register define.
I found the datasheet of OTM3225A. I think you can change
the hardcoding for readability.
(https://www.crystalfontz.com/controllers/OriseTech/OTM3225A/196/)

For example, you can add register define and change display_on[]
as below.

#define DISPLAY_CONTROL_1		0x07
#define POWER_CONTROL_1			0x10

+static struct otm3225a_spi_instruction display_on[] = {
+	{ POWER_CONTROL_1, 0x1280, 0 },
+	{ DISPLAY_CONTROL_1, 0x0101, 100 },
+	{ DISPLAY_CONTROL_1, 0x0121, 0 },
+	{ DISPLAY_CONTROL_1, 0x0123, 100 },
+	{ DISPLAY_CONTROL_1, 0x0133, 10 },
+};

> +
> +static void otm3225a_write(struct spi_device *spi,
> +			   struct otm3225a_spi_instruction *instruction,
> +			   unsigned int count)
> +{
> +	unsigned char buf[3];
> +
> +	while (count--) {
> +		/* address register using index register */
> +		buf[0] = OTM3225A_INDEX_REG;
> +		buf[1] = 0x00;
> +		buf[2] = instruction->reg;
> +		spi_write(spi, buf, 3);
> +
> +		/* write data to addressed register */
> +		buf[0] = OTM3225A_DATA_REG;
> +		buf[1] = (instruction->value >> 8) & 0xff;
> +		buf[2] = instruction->value & 0xff;
> +		spi_write(spi, buf, 3);
> +
> +		/* execute delay if any */
> +		mdelay(instruction->delay);

Please use msleep instead of mdelay.

> +		instruction++;
> +	}
> +}
> +
> +static int otm3225a_set_power(struct lcd_device *ld, int power)
> +{
> +	struct otm3225a_data *dd = lcd_get_data(ld);
> +
> +	if (power == dd->power)
> +		return 0;
> +
> +	if (power > FB_BLANK_UNBLANK)
> +		otm3225a_write(dd->spi, display_off,
> ARRAY_SIZE(display_off));
> +	else
> +		otm3225a_write(dd->spi, display_on, ARRAY_SIZE(display_on));
> +	dd->power = power;
> +
> +	return 0;
> +}
> +
> +static int otm3225a_get_power(struct lcd_device *ld)
> +{
> +	struct otm3225a_data *dd = lcd_get_data(ld);
> +
> +	return dd->power;
> +}
> +
> +struct lcd_ops otm3225a_ops = {
> +	.set_power = otm3225a_set_power,
> +	.get_power = otm3225a_get_power,
> +};
> +
> +static int otm3225a_probe(struct spi_device *spi)
> +{
> +	struct otm3225a_data *dd;
> +	struct lcd_device *ld;
> +	int ret = 0;
> +
> +	dd = kzalloc(sizeof(struct otm3225a_data), GFP_KERNEL);

Please use devm_kzalloc(), then you don't need to use kfree(dd)
in otm3225a_remove().

> +	if (dd == NULL) {
> +		ret = -ENOMEM;
> +		goto err;
> +	}
> +
> +	ld = lcd_device_register("otm3225a", &spi->dev, dd, &otm3225a_ops);

Please use devm_lcd_device_register(), then you don't need
to use lcd_device_unregister() in otm3225a_remove().

> +	if (IS_ERR(ld)) {
> +		ret = PTR_ERR(ld);
> +		goto err;
> +	}
> +	dd->spi = spi;
> +	dd->ld = ld;
> +	dev_set_drvdata(&spi->dev, dd);
> +
> +	dev_info(&spi->dev, "Initializing and switching to RGB interface");
> +	otm3225a_write(spi, display_init, ARRAY_SIZE(display_init));
> +	otm3225a_write(spi, display_enable_rgb_interface,
> +		       ARRAY_SIZE(display_enable_rgb_interface));
> +
> +err:
> +	return ret;
> +}
> +
> +static int otm3225a_remove(struct spi_device *spi)
> +{
> +	struct otm3225a_data *dd;
> +
> +	dd = dev_get_drvdata(&spi->dev);
> +	lcd_device_unregister(dd->ld);
> +	kfree(dd);

If you use devm_kzalloc() and devm_lcd_device_register()
in otm3225a_probe as I mentioned above, you can remove
lcd_device_unregister() and kfree() here.

If so, you don't need otm3225a_remove().
What I want to say is that you can add only probe() function
when you use devm_* functions in your otm3225a driver code.

> +	return 0;
> +}
> +
> +static struct spi_driver otm3225a_driver = {
> +	.driver = {
> +		.name = "otm3225a",
> +		.owner = THIS_MODULE,
> +	},
> +	.probe = otm3225a_probe,
> +	.remove = otm3225a_remove,

If you use devm_kzalloc() and devm_lcd_device_register(),
you can remove otm3225a_remove() as below.

+static struct spi_driver otm3225a_driver = {
+	.driver = {
+		.name = "otm3225a",
+		.owner = THIS_MODULE,
+	},
+	.probe = otm3225a_probe,
+};

Please refer to the following driver.
./drivers/video/backlight/tps65217_bl.c

> +};
> +
> +static __init int otm3225a_init(void)
> +{
> +	return (&otm3225a_driver);
> +}
> +
> +static __exit void otm3225a_exit(void)
> +{
> +	spi_unregister_driver(&otm3225a_driver);
> +}
> +
> +module_init(otm3225a_init);
> +module_exit(otm3225a_exit);

Instead of adding otm3225a_init(), otm3225a_exit(), 
please use module_spi_driver macro as below.
This macro can reduce source code lines.

module_spi_driver(otm3225a_driver);

Best regards,
Jingoo Han

> +
> +MODULE_AUTHOR("Felix Brack <fb@...c.ch>");
> +MODULE_DESCRIPTION("OTM3225A TFT LCD driver");
> +MODULE_VERSION("1.0.0");
> +MODULE_LICENSE("GPL v2");
> --
> 2.7.4

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