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[2620:137:e000::1:20]) by mx.google.com with ESMTP id pf14-20020a17090b1d8e00b00262e77d645asi7461981pjb.174.2023.07.22.11.24.42; Sat, 22 Jul 2023 11:24:55 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=fail header.i=@hugovil.com header.s=x header.b=ExLZ1Qy+; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229654AbjGVSJe (ORCPT + 99 others); Sat, 22 Jul 2023 14:09:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229468AbjGVSJc (ORCPT ); Sat, 22 Jul 2023 14:09:32 -0400 Received: from mail.hugovil.com (mail.hugovil.com [162.243.120.170]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F0BC82137 for ; Sat, 22 Jul 2023 11:09:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=hugovil.com ; s=x; h=Subject:Content-Transfer-Encoding:MIME-Version:Message-Id:Date:Cc:To :From:Sender:Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date :Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Id:List-Help:List-Unsubscribe:List-Subscribe:List-Post: List-Owner:List-Archive; bh=bstB9YlCqNA/WOhFlcxMzxMgJHMc9Q6yy29zfQ9Xe3M=; b=E xLZ1Qy+OxQDAr0kxZHJFU7K62rQXwlDAWNsoNo5PzkboETIwkY4jehoFA9xevYWwUgzAn6/Yxhv0V KiUW5TAKRIpdW21SH0+FnTDVO9Zm9rr8TI9lsdjXrJgqIA9gh8g20HMIeVvVstLM2xb1kCPlRUx/R UrGJ6vKr06E9Hi7M=; Received: from modemcable061.19-161-184.mc.videotron.ca ([184.161.19.61]:49762 helo=localhost.localdomain) by mail.hugovil.com with esmtpa (Exim 4.92) (envelope-from ) id 1qNH2n-0004G1-99; Sat, 22 Jul 2023 14:09:29 -0400 From: Hugo Villeneuve To: Miguel Ojeda Cc: hugo@hugovil.com, Hugo Villeneuve , linux-kernel@vger.kernel.org Date: Sat, 22 Jul 2023 14:09:25 -0400 Message-Id: <20230722180925.1408885-1-hugo@hugovil.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 184.161.19.61 X-SA-Exim-Mail-From: hugo@hugovil.com X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Spam-Level: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_PASS,SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 Subject: [PATCH v2] auxdisplay: hd44780: move cursor home after clear display command X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on mail.hugovil.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1772146178433251230 X-GMAIL-MSGID: 1772146178433251230 From: Hugo Villeneuve The DISPLAY_CLEAR command on the NewHaven NHD-0220DZW-AG5 display does NOT change the DDRAM address to 00h (home position) like the standard Hitachi HD44780 controller. As a consequence, the starting position of the initial string LCD_INIT_TEXT is not guaranteed to be at 0,0 depending on where the cursor was before the DISPLAY_CLEAR command. Extract of DISPLAY_CLEAR command from datasheets of: Hitachi HD44780: ... It then sets DDRAM address 0 into the address counter... NewHaven NHD-0220DZW-AG5 datasheet: ... This instruction does not change the DDRAM Address Move the cursor home after sending DISPLAY_CLEAR command to support non-standard LCDs. Signed-off-by: Hugo Villeneuve Reviewed-by: Geert Uytterhoeven Tested-by: David Reaver --- drivers/auxdisplay/hd44780_common.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) base-commit: d192f5382581d972c4ae1b4d72e0b59b34cadeb9 diff --git a/drivers/auxdisplay/hd44780_common.c b/drivers/auxdisplay/hd44780_common.c index 3934c2eebf33..7cbf375b0fa5 100644 --- a/drivers/auxdisplay/hd44780_common.c +++ b/drivers/auxdisplay/hd44780_common.c @@ -82,7 +82,15 @@ int hd44780_common_clear_display(struct charlcd *lcd) hdc->write_cmd(hdc, LCD_CMD_DISPLAY_CLEAR); /* datasheet says to wait 1,64 milliseconds */ long_sleep(2); - return 0; + + /* + * The Hitachi HD44780 controller (and compatible ones) reset the DDRAM + * address when executing the DISPLAY_CLEAR command, thus the + * following call is not required. However, other controllers do not + * (e.g. NewHaven NHD-0220DZW-AG5), thus move the cursor to home + * unconditionally to support both. + */ + return hd44780_common_home(lcd); } EXPORT_SYMBOL_GPL(hd44780_common_clear_display);