From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E8E9C0015E for ; Tue, 25 Jul 2023 15:14:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232877AbjGYPOG (ORCPT ); Tue, 25 Jul 2023 11:14:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42868 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232819AbjGYPOC (ORCPT ); Tue, 25 Jul 2023 11:14:02 -0400 Received: from mail.hugovil.com (mail.hugovil.com [162.243.120.170]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B97731BD9 for ; Tue, 25 Jul 2023 08:14:00 -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:Content-Type:Mime-Version: References:In-Reply-To:Message-Id:Cc:To:From:Date:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=BV1xB/2XbmJZJAGcy1cpgotCP6ChotEIwq9HRVIEYeY=; b=NWkwQWiG7sj2qpHxVC3/1m2x2L YABumZgyt/lBp/yaJkXDEUZmKPwiq1wkTqiRXuUsBNn7wqAFIpmBqnjLN3hvLTbmO+olrTeKrb7E/ B71F01nH7+lh+Vt80zSa6WCxWbtkHmXbMKMcQoe9iNhuobr//Ox/PzODxIhMc1oBIEc0=; Received: from modemcable061.19-161-184.mc.videotron.ca ([184.161.19.61]:39448 helo=pettiford) by mail.hugovil.com with esmtpa (Exim 4.92) (envelope-from ) id 1qOJjX-0003j2-87; Tue, 25 Jul 2023 11:13:55 -0400 Date: Tue, 25 Jul 2023 11:13:54 -0400 From: Hugo Villeneuve To: Geert Uytterhoeven Cc: Miguel Ojeda , Hugo Villeneuve , linux-kernel@vger.kernel.org Message-Id: <20230725111354.160f32cfba0b53923ac2aae6@hugovil.com> In-Reply-To: References: <20230722180925.1408885-1-hugo@hugovil.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 184.161.19.61 X-SA-Exim-Mail-From: hugo@hugovil.com Subject: Re: [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 On Mon, 24 Jul 2023 18:08:00 +0200 Geert Uytterhoeven wrote: > Hi Hugo, > > On Sat, Jul 22, 2023 at 8:18 PM Hugo Villeneuve wrote: > > 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 > > Thanks for your patch! > > > --- 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); > > Sorry, I haven't tested your patch yet, as my HD44780 display is > currently not connected to any system. > > Your patch LGTM, so > Reviewed-by: Geert Uytterhoeven > > Note that hd44780_common_home() calls hd44780_common_gotoxy(). > According to the documentation, both HD44780U and NHD-0220DZW-AG5 > support the Return Home command (0x02), so that could be a good > alternative. Hi Geert, If this is desired, I think maybe it would be best to do it in a separate patch. Maybe there is a good reason why hd44780_common_home() calls hd44780_common_gotoxy() instead of using Return Home command? Hugo. > > > } > > EXPORT_SYMBOL_GPL(hd44780_common_clear_display); > > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds >