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Commit ac201479 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Greg Kroah-Hartman
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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: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 39f8ea46

drivers/auxdisplay/charlcd.c

+30 −6
Original line number Diff line number Diff line
@@ -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);

	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);



	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;

include/misc/charlcd.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

};