linux-kernel - [PATCH v4 26/32] auxdisplay: hd44780_common: Reduce clear

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Message-Id: <20201005130128.3430804-14-poeschel@lemonage.de>
Date:   Mon,  5 Oct 2020 15:01:22 +0200
From:   poeschel@...onage.de
To:     Miguel Ojeda Sandonis <miguel.ojeda.sandonis@...il.com>,
        linux-kernel@...r.kernel.org (open list)
Cc:     Lars Poeschel <poeschel@...onage.de>
Subject: [PATCH v4 26/32] auxdisplay: hd44780_common: Reduce clear_display timeout

From: Lars Poeschel <poeschel@...onage.de>

Digging in the hd44780 datasheet revealed that the timeout needed after
clearing the whole display is only 1,64ms not 15ms. So we can reduce
that timeout.

Link: https://lore.kernel.org/lkml/20200922092121.GG16421@1wt.eu/
Link: https://www.crystalfontz.com/controllers/Hitachi/HD44780/433/

Signed-off-by: Lars Poeschel <poeschel@...onage.de>
---
Changes in v3:
- This patch is new in v3
---
 drivers/auxdisplay/hd44780_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/auxdisplay/hd44780_common.c b/drivers/auxdisplay/hd44780_common.c
index 82afae78f46e..fbce8835a650 100644
--- a/drivers/auxdisplay/hd44780_common.c
+++ b/drivers/auxdisplay/hd44780_common.c
@@ -83,8 +83,8 @@ 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);
+	/* datasheet says to wait 1,64 milliseconds */
+	long_sleep(2);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(hd44780_common_clear_display);
-- 
2.28.0