A user has no way of unshifting the display programmatically once shifted. Users cannot rely on ^[[H (home) to result in their message being seen either. Use the actual HOME command 0x02 instead of only returning to x0/y0. Users can still do ^[[Lx0y0; (go to x/y) if they wish to use the 'old' home function. Implement fast clearing of LCD by going to x0/y0 first, clearing display and then calling home to possibly unshift display possibly avoiding artifacts by not unshifting before clearing display.
Signed-off-by: Robert Abel <[email protected]> --- drivers/auxdisplay/charlcd.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c index ae078f414539..fdb3aa6423bf 100644 --- a/drivers/auxdisplay/charlcd.c +++ b/drivers/auxdisplay/charlcd.c @@ -43,6 +43,8 @@ /* LCD commands */ #define LCD_CMD_DISPLAY_CLEAR 0x01 /* Clear entire display */ +#define LCD_CMD_HOME 0x02 /* Set DDRAM address to 0 and unshift display */ + #define LCD_CMD_ENTRY_MODE 0x04 /* Set entry mode */ #define LCD_CMD_CURSOR_INC 0x02 /* Increment cursor */ @@ -174,13 +176,24 @@ static void charlcd_gotoxy(struct charlcd *lcd) lcd->ops->write_cmd(lcd, LCD_CMD_SET_DDRAM_ADDR | addr); } +/** + * charlcd_home() - Return to DDRAM address 0 and unshift the display. + * @lcd: LCD descriptor structure. + * + * Return to coordinates x0/y0 and unshift the display. + * + * Note: Use the movement command ^[[Lx0y0; instead of home + * in case the display should not be unshifted. + */ static void charlcd_home(struct charlcd *lcd) { struct charlcd_priv *priv = to_priv(lcd); + /* return to x0/y0 and unshift the display */ priv->addr.x = 0; priv->addr.y = 0; - charlcd_gotoxy(lcd); + lcd->ops->write_cmd(lcd, LCD_CMD_HOME); + long_sleep(2); } static void charlcd_print(struct charlcd *lcd, char c) @@ -198,11 +211,21 @@ static void charlcd_print(struct charlcd *lcd, char c) charlcd_gotoxy(lcd); } +/** + * charlcd_clear_fast() - Perform a fast clear of the display and return home. + * @lcd: LCD descriptor structure. + * + * The display will be unshifted and at coordinates x0/y0 after fast clear. + */ static void charlcd_clear_fast(struct charlcd *lcd) { + struct charlcd_priv *priv = to_priv(lcd); int pos; - charlcd_home(lcd); + /* avoid artifacts by going to x0/y0 without unshifting the display */ + priv->addr.x = 0; + priv->addr.y = 0; + charlcd_gotoxy(lcd); if (lcd->ops->clear_fast) lcd->ops->clear_fast(lcd); @@ -210,6 +233,7 @@ static void charlcd_clear_fast(struct charlcd *lcd) for (pos = 0; pos < min(2, lcd->height) * lcd->hwidth; pos++) lcd->ops->write_data(lcd, ' '); + /* return to x0/y0 and unshift the display */ charlcd_home(lcd); } -- 2.11.0
