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>

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index 930ffb2fb31787c50d1fea5f2299d6a77b963691..b3a84e90a268478c91d3dd6bef2295e5aec9580f 100644 (file)
--- 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 c40047b673c9ea099160366857103e497c541cee..23f61850f3639ae1686f9f83e0bac6e6a5015ba5 100644 (file)
--- 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);
 };