auxdisplay: Move clear_display to hd44780_common

This moves the clear_display function from charlcd to hd44780_common.
This is one more step to make charlcd independent from device specific
code. The two hd44780 drivers use the new function from hd44780_common
and charlcd calls this function through its function pointer in its ops
structure.

Reviewed-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/auxdisplay/hd44780_common.c b/drivers/auxdisplay/hd44780_common.c
index ea62beada9d8..2f7d55668eb4 100644
--- a/drivers/auxdisplay/hd44780_common.c
+++ b/drivers/auxdisplay/hd44780_common.c
@@ -1,13 +1,22 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 #include <linux/module.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 
 #include "charlcd.h"
 #include "hd44780_common.h"
 
 /* LCD commands */
+#define LCD_CMD_DISPLAY_CLEAR	0x01	/* Clear entire display */
+
 #define LCD_CMD_SET_DDRAM_ADDR	0x80	/* Set display data RAM address */
 
+/* sleeps that many milliseconds with a reschedule */
+static void long_sleep(int ms)
+{
+	schedule_timeout_interruptible(msecs_to_jiffies(ms));
+}
+
 int hd44780_common_print(struct charlcd *lcd, int c)
 {
 	struct hd44780_common *hdc = lcd->drvdata;
@@ -49,6 +58,18 @@ int hd44780_common_home(struct charlcd *lcd)
 }
 EXPORT_SYMBOL_GPL(hd44780_common_home);
 
+/* clears the display and resets X/Y */
+int hd44780_common_clear_display(struct charlcd *lcd)
+{
+	struct hd44780_common *hdc = lcd->drvdata;
+
+	hdc->write_cmd(hdc, LCD_CMD_DISPLAY_CLEAR);
+	/* we must wait a few milliseconds (15) */
+	long_sleep(15);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hd44780_common_clear_display);
+
 struct hd44780_common *hd44780_common_alloc(void)
 {
 	struct hd44780_common *hd;