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auxdisplay: charlcd: Add support for 4-bit interfaces 

In 4-bit mode, 8-bit commands and data are written using two raw writes
to the data interface: high nibble first, low nibble last.  This must be
handled by the low-level driver.

However, as we don't know in which mode (4-bit or 8-bit) nor 4-bit phase
the LCD was left, initialization must always be handled using raw
writes, and needs to configure the LCD for 8-bit mode first.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Geert Uytterhoeven 2017-03-10 15:15:18 +01:00 committed by Greg Kroah-Hartman
parent 39f8ea4672
commit ac201479cc
2 changed files with 32 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
drivers/auxdisplay/charlcd.c
View File

@ -223,24 +223,46 @@ static void charlcd_clear_display(struct charlcd *lcd)
static int charlcd_init_display(struct charlcd *lcd)
{
void (*write_cmd_raw)(struct charlcd *lcd, int cmd);
struct charlcd_priv *priv = to_priv(lcd);
u8 init;
if (lcd->ifwidth != 4 && lcd->ifwidth != 8)
return -EINVAL;
priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
LCD_FLAG_C | LCD_FLAG_B;
long_sleep(20); /* wait 20 ms after power-up for the paranoid */
/* 8bits, 1 line, small fonts; let's do it 3 times */
lcd->ops->write_cmd(lcd, LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS);
/*
* 8-bit mode, 1 line, small fonts; let's do it 3 times, to make sure
* the LCD is in 8-bit mode afterwards
*/
init = LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS;
if (lcd->ifwidth == 4) {
init >>= 4;
write_cmd_raw = lcd->ops->write_cmd_raw4;
} else {
write_cmd_raw = lcd->ops->write_cmd;
}
write_cmd_raw(lcd, init);
long_sleep(10);
lcd->ops->write_cmd(lcd, LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS);
write_cmd_raw(lcd, init);
long_sleep(10);
lcd->ops->write_cmd(lcd, LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS);
write_cmd_raw(lcd, init);
long_sleep(10);
if (lcd->ifwidth == 4) {
/* Switch to 4-bit mode, 1 line, small fonts */
lcd->ops->write_cmd_raw4(lcd, LCD_CMD_FUNCTION_SET >> 4);
long_sleep(10);
}
/* set font height and lines number */
lcd->ops->write_cmd(lcd,
LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS |
LCD_CMD_FUNCTION_SET |
((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
long_sleep(10);
@ -482,7 +504,8 @@ static inline int handle_lcd_special_code(struct charlcd *lcd)
/* check whether one of F,N flags was changed */
else if ((oldflags ^ priv->flags) & (LCD_FLAG_F | LCD_FLAG_N))
lcd->ops->write_cmd(lcd,
LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS |
LCD_CMD_FUNCTION_SET |
((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
/* check whether L flag was changed */
@ -716,6 +739,7 @@ struct charlcd *charlcd_alloc(unsigned int drvdata_size)
priv->esc_seq.len = -1;
lcd = &priv->lcd;
lcd->ifwidth = 8;
lcd->bwidth = DEFAULT_LCD_BWIDTH;
lcd->hwidth = DEFAULT_LCD_HWIDTH;
lcd->drvdata = priv->drvdata;

2
include/misc/charlcd.h
View File

@ -14,6 +14,7 @@ struct charlcd {
const struct charlcd_ops *ops;
const unsigned char *char_conv; /* Optional */
int ifwidth; /* 4-bit or 8-bit (default) */
int height;
int width;
int bwidth; /* Default set by charlcd_alloc() */
@ -28,6 +29,7 @@ struct charlcd_ops {
void (*write_data)(struct charlcd *lcd, int data);
/* Optional */
void (*write_cmd_raw4)(struct charlcd *lcd, int cmd); /* 4-bit only */
void (*clear_fast)(struct charlcd *lcd);
void (*backlight)(struct charlcd *lcd, int on);
};