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linux-next/drivers/video/backlight/ili922x.c
Colin Ian King 29fae2c1db backlight: ili922x: Remove redundant variable len 
The variable len is assigned but never read, therefore it is redundant
and can be removed. Cleans up clang warning:

drivers/video/backlight/ili922x.c:276:2: warning: Value stored to 'len'
is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
2017-11-08 10:43:49 +00:00

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/*
* (C) Copyright 2008
* Stefano Babic, DENX Software Engineering, sbabic@denx.de.
*
* 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 driver implements a lcd device for the ILITEK 922x display
* controller. The interface to the display is SPI and the display's
* memory is cyclically updated over the RGB interface.
*/
#include <linux/fb.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/lcd.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/string.h>
/* Register offset, see manual section 8.2 */
#define REG_START_OSCILLATION 0x00
#define REG_DRIVER_CODE_READ 0x00
#define REG_DRIVER_OUTPUT_CONTROL 0x01
#define REG_LCD_AC_DRIVEING_CONTROL 0x02
#define REG_ENTRY_MODE 0x03
#define REG_COMPARE_1 0x04
#define REG_COMPARE_2 0x05
#define REG_DISPLAY_CONTROL_1 0x07
#define REG_DISPLAY_CONTROL_2 0x08
#define REG_DISPLAY_CONTROL_3 0x09
#define REG_FRAME_CYCLE_CONTROL 0x0B
#define REG_EXT_INTF_CONTROL 0x0C
#define REG_POWER_CONTROL_1 0x10
#define REG_POWER_CONTROL_2 0x11
#define REG_POWER_CONTROL_3 0x12
#define REG_POWER_CONTROL_4 0x13
#define REG_RAM_ADDRESS_SET 0x21
#define REG_WRITE_DATA_TO_GRAM 0x22
#define REG_RAM_WRITE_MASK1 0x23
#define REG_RAM_WRITE_MASK2 0x24
#define REG_GAMMA_CONTROL_1 0x30
#define REG_GAMMA_CONTROL_2 0x31
#define REG_GAMMA_CONTROL_3 0x32
#define REG_GAMMA_CONTROL_4 0x33
#define REG_GAMMA_CONTROL_5 0x34
#define REG_GAMMA_CONTROL_6 0x35
#define REG_GAMMA_CONTROL_7 0x36
#define REG_GAMMA_CONTROL_8 0x37
#define REG_GAMMA_CONTROL_9 0x38
#define REG_GAMMA_CONTROL_10 0x39
#define REG_GATE_SCAN_CONTROL 0x40
#define REG_VERT_SCROLL_CONTROL 0x41
#define REG_FIRST_SCREEN_DRIVE_POS 0x42
#define REG_SECOND_SCREEN_DRIVE_POS 0x43
#define REG_RAM_ADDR_POS_H 0x44
#define REG_RAM_ADDR_POS_V 0x45
#define REG_OSCILLATOR_CONTROL 0x4F
#define REG_GPIO 0x60
#define REG_OTP_VCM_PROGRAMMING 0x61
#define REG_OTP_VCM_STATUS_ENABLE 0x62
#define REG_OTP_PROGRAMMING_ID_KEY 0x65
/*
* maximum frequency for register access
* (not for the GRAM access)
*/
#define ILITEK_MAX_FREQ_REG 4000000
/*
* Device ID as found in the datasheet (supports 9221 and 9222)
*/
#define ILITEK_DEVICE_ID 0x9220
#define ILITEK_DEVICE_ID_MASK 0xFFF0
/* Last two bits in the START BYTE */
#define START_RS_INDEX 0
#define START_RS_REG 1
#define START_RW_WRITE 0
#define START_RW_READ 1
/**
* START_BYTE(id, rs, rw)
*
* Set the start byte according to the required operation.
* The start byte is defined as:
* ----------------------------------
* | 0 | 1 | 1 | 1 | 0 | ID | RS | RW |
* ----------------------------------
* @id: display's id as set by the manufacturer
* @rs: operation type bit, one of:
* - START_RS_INDEX set the index register
* - START_RS_REG write/read registers/GRAM
* @rw: read/write operation
* - START_RW_WRITE write
* - START_RW_READ read
*/
#define START_BYTE(id, rs, rw) \
(0x70 | (((id) & 0x01) << 2) | (((rs) & 0x01) << 1) | ((rw) & 0x01))
/**
* CHECK_FREQ_REG(spi_device s, spi_transfer x) - Check the frequency
* for the SPI transfer. According to the datasheet, the controller
* accept higher frequency for the GRAM transfer, but it requires
* lower frequency when the registers are read/written.
* The macro sets the frequency in the spi_transfer structure if
* the frequency exceeds the maximum value.
*/
#define CHECK_FREQ_REG(s, x) \
do { \
if (s->max_speed_hz > ILITEK_MAX_FREQ_REG) \
((struct spi_transfer *)x)->speed_hz = \
ILITEK_MAX_FREQ_REG; \
} while (0)
#define CMD_BUFSIZE 16
#define POWER_IS_ON(pwr) ((pwr) <= FB_BLANK_NORMAL)
#define set_tx_byte(b) (tx_invert ? ~(b) : b)
/**
* ili922x_id - id as set by manufacturer
*/
static int ili922x_id = 1;
module_param(ili922x_id, int, 0);
static int tx_invert;
module_param(tx_invert, int, 0);
/**
* driver's private structure
*/
struct ili922x {
struct spi_device *spi;
struct lcd_device *ld;
int power;
};
/**
* ili922x_read_status - read status register from display
* @spi: spi device
* @rs: output value
*/
static int ili922x_read_status(struct spi_device *spi, u16 *rs)
{
struct spi_message msg;
struct spi_transfer xfer;
unsigned char tbuf[CMD_BUFSIZE];
unsigned char rbuf[CMD_BUFSIZE];
int ret, i;
memset(&xfer, 0, sizeof(struct spi_transfer));
spi_message_init(&msg);
xfer.tx_buf = tbuf;
xfer.rx_buf = rbuf;
xfer.cs_change = 1;
CHECK_FREQ_REG(spi, &xfer);
tbuf[0] = set_tx_byte(START_BYTE(ili922x_id, START_RS_INDEX,
START_RW_READ));
/*
* we need 4-byte xfer here due to invalid dummy byte
* received after start byte
*/
for (i = 1; i < 4; i++)
tbuf[i] = set_tx_byte(0); /* dummy */
xfer.bits_per_word = 8;
xfer.len = 4;
spi_message_add_tail(&xfer, &msg);
ret = spi_sync(spi, &msg);
if (ret < 0) {
dev_dbg(&spi->dev, "Error sending SPI message 0x%x", ret);
return ret;
}
*rs = (rbuf[2] << 8) + rbuf[3];
return 0;
}
/**
* ili922x_read - read register from display
* @spi: spi device
* @reg: offset of the register to be read
* @rx: output value
*/
static int ili922x_read(struct spi_device *spi, u8 reg, u16 *rx)
{
struct spi_message msg;
struct spi_transfer xfer_regindex, xfer_regvalue;
unsigned char tbuf[CMD_BUFSIZE];
unsigned char rbuf[CMD_BUFSIZE];
int ret, len = 0, send_bytes;
memset(&xfer_regindex, 0, sizeof(struct spi_transfer));
memset(&xfer_regvalue, 0, sizeof(struct spi_transfer));
spi_message_init(&msg);
xfer_regindex.tx_buf = tbuf;
xfer_regindex.rx_buf = rbuf;
xfer_regindex.cs_change = 1;
CHECK_FREQ_REG(spi, &xfer_regindex);
tbuf[0] = set_tx_byte(START_BYTE(ili922x_id, START_RS_INDEX,
START_RW_WRITE));
tbuf[1] = set_tx_byte(0);
tbuf[2] = set_tx_byte(reg);
xfer_regindex.bits_per_word = 8;
len = xfer_regindex.len = 3;
spi_message_add_tail(&xfer_regindex, &msg);
send_bytes = len;
tbuf[len++] = set_tx_byte(START_BYTE(ili922x_id, START_RS_REG,
START_RW_READ));
tbuf[len++] = set_tx_byte(0);
tbuf[len] = set_tx_byte(0);
xfer_regvalue.cs_change = 1;
xfer_regvalue.len = 3;
xfer_regvalue.tx_buf = &tbuf[send_bytes];
xfer_regvalue.rx_buf = &rbuf[send_bytes];
CHECK_FREQ_REG(spi, &xfer_regvalue);
spi_message_add_tail(&xfer_regvalue, &msg);
ret = spi_sync(spi, &msg);
if (ret < 0) {
dev_dbg(&spi->dev, "Error sending SPI message 0x%x", ret);
return ret;
}
*rx = (rbuf[1 + send_bytes] << 8) + rbuf[2 + send_bytes];
return 0;
}
/**
* ili922x_write - write a controller register
* @spi: struct spi_device *
* @reg: offset of the register to be written
* @value: value to be written
*/
static int ili922x_write(struct spi_device *spi, u8 reg, u16 value)
{
struct spi_message msg;
struct spi_transfer xfer_regindex, xfer_regvalue;
unsigned char tbuf[CMD_BUFSIZE];
unsigned char rbuf[CMD_BUFSIZE];
int ret;
memset(&xfer_regindex, 0, sizeof(struct spi_transfer));
memset(&xfer_regvalue, 0, sizeof(struct spi_transfer));
spi_message_init(&msg);
xfer_regindex.tx_buf = tbuf;
xfer_regindex.rx_buf = rbuf;
xfer_regindex.cs_change = 1;
CHECK_FREQ_REG(spi, &xfer_regindex);
tbuf[0] = set_tx_byte(START_BYTE(ili922x_id, START_RS_INDEX,
START_RW_WRITE));
tbuf[1] = set_tx_byte(0);
tbuf[2] = set_tx_byte(reg);
xfer_regindex.bits_per_word = 8;
xfer_regindex.len = 3;
spi_message_add_tail(&xfer_regindex, &msg);
ret = spi_sync(spi, &msg);
spi_message_init(&msg);
tbuf[0] = set_tx_byte(START_BYTE(ili922x_id, START_RS_REG,
START_RW_WRITE));
tbuf[1] = set_tx_byte((value & 0xFF00) >> 8);
tbuf[2] = set_tx_byte(value & 0x00FF);
xfer_regvalue.cs_change = 1;
xfer_regvalue.len = 3;
xfer_regvalue.tx_buf = tbuf;
xfer_regvalue.rx_buf = rbuf;
CHECK_FREQ_REG(spi, &xfer_regvalue);
spi_message_add_tail(&xfer_regvalue, &msg);
ret = spi_sync(spi, &msg);
if (ret < 0) {
dev_err(&spi->dev, "Error sending SPI message 0x%x", ret);
return ret;
}
return 0;
}
#ifdef DEBUG
/**
* ili922x_reg_dump - dump all registers
*/
static void ili922x_reg_dump(struct spi_device *spi)
{
u8 reg;
u16 rx;
dev_dbg(&spi->dev, "ILI922x configuration registers:\n");
for (reg = REG_START_OSCILLATION;
reg <= REG_OTP_PROGRAMMING_ID_KEY; reg++) {
ili922x_read(spi, reg, &rx);
dev_dbg(&spi->dev, "reg @ 0x%02X: 0x%04X\n", reg, rx);
}
}
#else
static inline void ili922x_reg_dump(struct spi_device *spi) {}
#endif
/**
* set_write_to_gram_reg - initialize the display to write the GRAM
* @spi: spi device
*/
static void set_write_to_gram_reg(struct spi_device *spi)
{
struct spi_message msg;
struct spi_transfer xfer;
unsigned char tbuf[CMD_BUFSIZE];
memset(&xfer, 0, sizeof(struct spi_transfer));
spi_message_init(&msg);
xfer.tx_buf = tbuf;
xfer.rx_buf = NULL;
xfer.cs_change = 1;
tbuf[0] = START_BYTE(ili922x_id, START_RS_INDEX, START_RW_WRITE);
tbuf[1] = 0;
tbuf[2] = REG_WRITE_DATA_TO_GRAM;
xfer.bits_per_word = 8;
xfer.len = 3;
spi_message_add_tail(&xfer, &msg);
spi_sync(spi, &msg);
}
/**
* ili922x_poweron - turn the display on
* @spi: spi device
*
* The sequence to turn on the display is taken from
* the datasheet and/or the example code provided by the
* manufacturer.
*/
static int ili922x_poweron(struct spi_device *spi)
{
int ret;
/* Power on */
ret = ili922x_write(spi, REG_POWER_CONTROL_1, 0x0000);
usleep_range(10000, 10500);
ret += ili922x_write(spi, REG_POWER_CONTROL_2, 0x0000);
ret += ili922x_write(spi, REG_POWER_CONTROL_3, 0x0000);
msleep(40);
ret += ili922x_write(spi, REG_POWER_CONTROL_4, 0x0000);
msleep(40);
/* register 0x56 is not documented in the datasheet */
ret += ili922x_write(spi, 0x56, 0x080F);
ret += ili922x_write(spi, REG_POWER_CONTROL_1, 0x4240);
usleep_range(10000, 10500);
ret += ili922x_write(spi, REG_POWER_CONTROL_2, 0x0000);
ret += ili922x_write(spi, REG_POWER_CONTROL_3, 0x0014);
msleep(40);
ret += ili922x_write(spi, REG_POWER_CONTROL_4, 0x1319);
msleep(40);
return ret;
}
/**
* ili922x_poweroff - turn the display off
* @spi: spi device
*/
static int ili922x_poweroff(struct spi_device *spi)
{
int ret;
/* Power off */
ret = ili922x_write(spi, REG_POWER_CONTROL_1, 0x0000);
usleep_range(10000, 10500);
ret += ili922x_write(spi, REG_POWER_CONTROL_2, 0x0000);
ret += ili922x_write(spi, REG_POWER_CONTROL_3, 0x0000);
msleep(40);
ret += ili922x_write(spi, REG_POWER_CONTROL_4, 0x0000);
msleep(40);
return ret;
}
/**
* ili922x_display_init - initialize the display by setting
* the configuration registers
* @spi: spi device
*/
static void ili922x_display_init(struct spi_device *spi)
{
ili922x_write(spi, REG_START_OSCILLATION, 1);
usleep_range(10000, 10500);
ili922x_write(spi, REG_DRIVER_OUTPUT_CONTROL, 0x691B);
ili922x_write(spi, REG_LCD_AC_DRIVEING_CONTROL, 0x0700);
ili922x_write(spi, REG_ENTRY_MODE, 0x1030);
ili922x_write(spi, REG_COMPARE_1, 0x0000);
ili922x_write(spi, REG_COMPARE_2, 0x0000);
ili922x_write(spi, REG_DISPLAY_CONTROL_1, 0x0037);
ili922x_write(spi, REG_DISPLAY_CONTROL_2, 0x0202);
ili922x_write(spi, REG_DISPLAY_CONTROL_3, 0x0000);
ili922x_write(spi, REG_FRAME_CYCLE_CONTROL, 0x0000);
/* Set RGB interface */
ili922x_write(spi, REG_EXT_INTF_CONTROL, 0x0110);
ili922x_poweron(spi);
ili922x_write(spi, REG_GAMMA_CONTROL_1, 0x0302);
ili922x_write(spi, REG_GAMMA_CONTROL_2, 0x0407);
ili922x_write(spi, REG_GAMMA_CONTROL_3, 0x0304);
ili922x_write(spi, REG_GAMMA_CONTROL_4, 0x0203);
ili922x_write(spi, REG_GAMMA_CONTROL_5, 0x0706);
ili922x_write(spi, REG_GAMMA_CONTROL_6, 0x0407);
ili922x_write(spi, REG_GAMMA_CONTROL_7, 0x0706);
ili922x_write(spi, REG_GAMMA_CONTROL_8, 0x0000);
ili922x_write(spi, REG_GAMMA_CONTROL_9, 0x0C06);
ili922x_write(spi, REG_GAMMA_CONTROL_10, 0x0F00);
ili922x_write(spi, REG_RAM_ADDRESS_SET, 0x0000);
ili922x_write(spi, REG_GATE_SCAN_CONTROL, 0x0000);
ili922x_write(spi, REG_VERT_SCROLL_CONTROL, 0x0000);
ili922x_write(spi, REG_FIRST_SCREEN_DRIVE_POS, 0xDB00);
ili922x_write(spi, REG_SECOND_SCREEN_DRIVE_POS, 0xDB00);
ili922x_write(spi, REG_RAM_ADDR_POS_H, 0xAF00);
ili922x_write(spi, REG_RAM_ADDR_POS_V, 0xDB00);
ili922x_reg_dump(spi);
set_write_to_gram_reg(spi);
}
static int ili922x_lcd_power(struct ili922x *lcd, int power)
{
int ret = 0;
if (POWER_IS_ON(power) && !POWER_IS_ON(lcd->power))
ret = ili922x_poweron(lcd->spi);
else if (!POWER_IS_ON(power) && POWER_IS_ON(lcd->power))
ret = ili922x_poweroff(lcd->spi);
if (!ret)
lcd->power = power;
return ret;
}
static int ili922x_set_power(struct lcd_device *ld, int power)
{
struct ili922x *ili = lcd_get_data(ld);
return ili922x_lcd_power(ili, power);
}
static int ili922x_get_power(struct lcd_device *ld)
{
struct ili922x *ili = lcd_get_data(ld);
return ili->power;
}
static struct lcd_ops ili922x_ops = {
.get_power = ili922x_get_power,
.set_power = ili922x_set_power,
};
static int ili922x_probe(struct spi_device *spi)
{
struct ili922x *ili;
struct lcd_device *lcd;
int ret;
u16 reg = 0;
ili = devm_kzalloc(&spi->dev, sizeof(*ili), GFP_KERNEL);
if (!ili)
return -ENOMEM;
ili->spi = spi;
spi_set_drvdata(spi, ili);
/* check if the device is connected */
ret = ili922x_read(spi, REG_DRIVER_CODE_READ, &reg);
if (ret || ((reg & ILITEK_DEVICE_ID_MASK) != ILITEK_DEVICE_ID)) {
dev_err(&spi->dev,
"no LCD found: Chip ID 0x%x, ret %d\n",
reg, ret);
return -ENODEV;
}
dev_info(&spi->dev, "ILI%x found, SPI freq %d, mode %d\n",
reg, spi->max_speed_hz, spi->mode);
ret = ili922x_read_status(spi, &reg);
if (ret) {
dev_err(&spi->dev, "reading RS failed...\n");
return ret;
}
dev_dbg(&spi->dev, "status: 0x%x\n", reg);
ili922x_display_init(spi);
ili->power = FB_BLANK_POWERDOWN;
lcd = devm_lcd_device_register(&spi->dev, "ili922xlcd", &spi->dev, ili,
&ili922x_ops);
if (IS_ERR(lcd)) {
dev_err(&spi->dev, "cannot register LCD\n");
return PTR_ERR(lcd);
}
ili->ld = lcd;
spi_set_drvdata(spi, ili);
ili922x_lcd_power(ili, FB_BLANK_UNBLANK);
return 0;
}
static int ili922x_remove(struct spi_device *spi)
{
ili922x_poweroff(spi);
return 0;
}
static struct spi_driver ili922x_driver = {
.driver = {
.name = "ili922x",
},
.probe = ili922x_probe,
.remove = ili922x_remove,
};
module_spi_driver(ili922x_driver);
MODULE_AUTHOR("Stefano Babic <sbabic@denx.de>");
MODULE_DESCRIPTION("ILI9221/9222 LCD driver");
MODULE_LICENSE("GPL");
MODULE_PARM_DESC(ili922x_id, "set controller identifier (default=1)");
MODULE_PARM_DESC(tx_invert, "invert bytes before sending");
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