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@xxxxxxxxxxxxxx>
---
v2:
- No changes.
---
drivers/auxdisplay/charlcd.c | 36 ++++++++++++++++++++++++++++++------
include/misc/charlcd.h | 2 ++
2 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index 930ffb2fb31787c5..b3a84e90a268478c 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -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;
diff --git a/include/misc/charlcd.h b/include/misc/charlcd.h
index c40047b673c9ea09..23f61850f3639ae1 100644
--- a/include/misc/charlcd.h
+++ b/include/misc/charlcd.h
@@ -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);
};
--
2.7.4
--
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