// SPDX-License-Identifier: GPL-2.0
/*
* Driver for the on-board character LCD found on some ARM reference boards
* This is basically an Hitachi HD44780 LCD with a custom IP block to drive it
* https://en.wikipedia.org/wiki/HD44780_Character_LCD
* Currently it will just display the text "ARM Linux" and the linux version
*
* Author: Linus Walleij <triad@df.lth.se>
*/
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <generated/utsrelease.h>
#define DRIVERNAME
"arm-charlcd"
#define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
/* Offsets to registers */
#define CHAR_COM 0x00U
#define CHAR_DAT 0x04U
#define CHAR_RD 0x08U
#define CHAR_RAW 0x0CU
#define CHAR_MASK 0x10U
#define CHAR_STAT 0x14U
#define CHAR_RAW_CLEAR 0x00000000U
#define CHAR_RAW_VALID 0x00000100U
/* Hitachi HD44780 display commands */
#define HD_CLEAR 0x01U
#define HD_HOME 0x02U
#define HD_ENTRYMODE 0x04U
#define HD_ENTRYMODE_INCREMENT 0x02U
#define HD_ENTRYMODE_SHIFT 0x01U
#define HD_DISPCTRL 0x08U
#define HD_DISPCTRL_ON 0x04U
#define HD_DISPCTRL_CURSOR_ON 0x02U
#define HD_DISPCTRL_CURSOR_BLINK 0x01U
#define HD_CRSR_SHIFT 0x10U
#define HD_CRSR_SHIFT_DISPLAY 0x08U
#define HD_CRSR_SHIFT_DISPLAY_RIGHT 0x04U
#define HD_FUNCSET 0x20U
#define HD_FUNCSET_8BIT 0x10U
#define HD_FUNCSET_2_LINES 0x08U
#define HD_FUNCSET_FONT_5X10 0x04U
#define HD_SET_CGRAM 0x40U
#define HD_SET_DDRAM 0x80U
#define HD_BUSY_FLAG 0x80U
/**
* struct charlcd - Private data structure
* @dev: a pointer back to containing device
* @phybase: the offset to the controller in physical memory
* @physize: the size of the physical page
* @virtbase: the offset to the controller in virtual memory
* @irq: reserved interrupt number
* @complete: completion structure for the last LCD command
* @init_work: delayed work structure to initialize the display on boot
*/
struct charlcd {
struct device *dev;
u32 phybase;
u32 physize;
void __iomem *virtbase;
int irq;
struct completion complete;
struct delayed_work init_work;
};
static irqreturn_t charlcd_interrupt(
int irq,
void *data)
{
struct charlcd *lcd = data;
u8 status;
status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
/* Clear IRQ */
writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
if (status)
complete(&lcd->complete);
else
dev_info(lcd->dev,
"Spurious IRQ (%02x)\n", status);
return IRQ_HANDLED;
}
static void charlcd_wait_complete_irq(
struct charlcd *lcd)
{
int ret;
ret = wait_for_completion_interruptible_timeout(&lcd->complete,
CHARLCD_TIMEOUT);
/* Disable IRQ after completion */
writel(0x00, lcd->virtbase + CHAR_MASK);
if (ret < 0) {
dev_err(lcd->dev,
"wait_for_completion_interruptible_timeout() "
"returned %d waiting for ready\n", ret);
return;
}
if (ret == 0) {
dev_err(lcd->dev,
"charlcd controller timed out "
"waiting for ready\n");
return;
}
}
static u8 charlcd_4bit_read_char(
struct charlcd *lcd)
{
u8 data;
u32 val;
int i;
/* If we can, use an IRQ to wait for the data, else poll */
if (lcd->irq >= 0)
charlcd_wait_complete_irq(lcd);
else {
i = 0;
val = 0;
while (!(val & CHAR_RAW_VALID) && i < 10) {
udelay(100);
val = readl(lcd->virtbase + CHAR_RAW);
i++;
}
writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
}
msleep(1);
/* Read the 4 high bits of the data */
data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
/*
* The second read for the low bits does not trigger an IRQ
* so in this case we have to poll for the 4 lower bits
*/
i = 0;
val = 0;
while (!(val & CHAR_RAW_VALID) && i < 10) {
udelay(100);
val = readl(lcd->virtbase + CHAR_RAW);
i++;
}
writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
msleep(1);
/* Read the 4 low bits of the data */
data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
return data;
}
static bool charlcd_4bit_read_bf(
struct charlcd *lcd)
{
if (lcd->irq >= 0) {
/*
* If we'll use IRQs to wait for the busyflag, clear any
* pending flag and enable IRQ
*/
writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
init_completion(&lcd->complete);
writel(0x01, lcd->virtbase + CHAR_MASK);
}
readl(lcd->virtbase + CHAR_COM);
return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ?
true :
false;
}
static void charlcd_4bit_wait_busy(
struct charlcd *lcd)
{
int retries = 50;
udelay(100);
while (charlcd_4bit_read_bf(lcd) && retries)
retries--;
if (!retries)
dev_err(lcd->dev,
"timeout waiting for busyflag\n");
}
static void charlcd_4bit_command(
struct charlcd *lcd, u8 cmd)
{
u32 cmdlo = (cmd << 4) & 0xf0;
u32 cmdhi = (cmd & 0xf0);
writel(cmdhi, lcd->virtbase + CHAR_COM);
udelay(10);
writel(cmdlo, lcd->virtbase + CHAR_COM);
charlcd_4bit_wait_busy(lcd);
}
static void charlcd_4bit_char(
struct charlcd *lcd, u8 ch)
{
u32 chlo = (ch << 4) & 0xf0;
u32 chhi = (ch & 0xf0);
writel(chhi, lcd->virtbase + CHAR_DAT);
udelay(10);
writel(chlo, lcd->virtbase + CHAR_DAT);
charlcd_4bit_wait_busy(lcd);
}
static void charlcd_4bit_print(
struct charlcd *lcd,
int line,
const char *str)
{
u8 offset;
int i;
/*
* We support line 0, 1
* Line 1 runs from 0x00..0x27
* Line 2 runs from 0x28..0x4f
*/
if (line == 0)
offset = 0;
else if (line == 1)
offset = 0x28;
else
return;
/* Set offset */
charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
/* Send string */
for (i = 0; i < strlen(str) && i < 0x28; i++)
charlcd_4bit_char(lcd, str[i]);
}
static void charlcd_4bit_init(
struct charlcd *lcd)
{
/* These commands cannot be checked with the busy flag */
writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
msleep(5);
writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
udelay(100);
writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
udelay(100);
/* Go to 4bit mode */
writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
udelay(100);
/*
* 4bit mode, 2 lines, 5x8 font, after this the number of lines
* and the font cannot be changed until the next initialization sequence
*/
charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
charlcd_4bit_command(lcd, HD_CLEAR);
charlcd_4bit_command(lcd, HD_HOME);
/* Put something useful in the display */
charlcd_4bit_print(lcd, 0,
"ARM Linux");
charlcd_4bit_print(lcd, 1, UTS_RELEASE);
}
static void charlcd_init_work(
struct work_struct *work)
{
struct charlcd *lcd =
container_of(work,
struct charlcd, init_work.work);
charlcd_4bit_init(lcd);
}
static int __init charlcd_probe(
struct platform_device *pdev)
{
int ret;
struct charlcd *lcd;
struct resource *res;
lcd = kzalloc(
sizeof(*lcd), GFP_KERNEL);
if (!lcd)
return -ENOMEM;
lcd->dev = &pdev->dev;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res) {
ret = -ENOENT;
goto out_no_resource;
}
lcd->phybase = res->start;
lcd->physize = resource_size(res);
if (request_mem_region(lcd->phybase, lcd->physize,
DRIVERNAME) == NULL) {
ret = -EBUSY;
goto out_no_memregion;
}
lcd->virtbase = ioremap(lcd->phybase, lcd->physize);
if (!lcd->virtbase) {
ret = -ENOMEM;
goto out_no_memregion;
}
lcd->irq = platform_get_irq(pdev, 0);
/* If no IRQ is supplied, we'll survive without it */
if (lcd->irq >= 0) {
if (request_irq(lcd->irq, charlcd_interrupt, 0,
DRIVERNAME, lcd)) {
ret = -EIO;
goto out_no_irq;
}
}
platform_set_drvdata(pdev, lcd);
/*
* Initialize the display in a delayed work, because
* it is VERY slow and would slow down the boot of the system.
*/
INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
schedule_delayed_work(&lcd->init_work, 0);
dev_info(&pdev->dev,
"initialized ARM character LCD at %08x\n",
lcd->phybase);
return 0;
out_no_irq:
iounmap(lcd->virtbase);
out_no_memregion:
release_mem_region(lcd->phybase, SZ_4K);
out_no_resource:
kfree(lcd);
return ret;
}
static int charlcd_suspend(
struct device *dev)
{
struct charlcd *lcd = dev_get_drvdata(dev);
/* Power the display off */
charlcd_4bit_command(lcd, HD_DISPCTRL);
return 0;
}
static int charlcd_resume(
struct device *dev)
{
struct charlcd *lcd = dev_get_drvdata(dev);
/* Turn the display back on */
charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
return 0;
}
static const struct dev_pm_ops charlcd_pm_ops = {
.suspend = charlcd_suspend,
.resume = charlcd_resume,
};
static const struct of_device_id charlcd_match[] = {
{ .compatible =
"arm,versatile-lcd", },
{}
};
static struct platform_driver charlcd_driver = {
.driver = {
.name = DRIVERNAME,
.pm = &charlcd_pm_ops,
.suppress_bind_attrs =
true,
.of_match_table = of_match_ptr(charlcd_match),
},
};
builtin_platform_driver_probe(charlcd_driver, charlcd_probe);
