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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A189EC07E95 for ; Mon, 19 Jul 2021 19:05:28 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 30873610CC for ; Mon, 19 Jul 2021 19:05:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 30873610CC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ravnborg.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id A18216E20A; Mon, 19 Jul 2021 19:05:26 +0000 (UTC) Received: from mx2.smtp.larsendata.com (mx2.smtp.larsendata.com [91.221.196.228]) by gabe.freedesktop.org (Postfix) with ESMTPS id 485526E20A for ; Mon, 19 Jul 2021 19:05:25 +0000 (UTC) Received: from mail01.mxhotel.dk (mail01.mxhotel.dk [91.221.196.236]) by mx2.smtp.larsendata.com (Halon) with ESMTPS id 4bfcbde5-e8c4-11eb-8d1a-0050568cd888; Mon, 19 Jul 2021 19:05:35 +0000 (UTC) Received: from ravnborg.org (80-162-45-141-cable.dk.customer.tdc.net [80.162.45.141]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: sam@ravnborg.org) by mail01.mxhotel.dk (Postfix) with ESMTPSA id ABD2C194B04; Mon, 19 Jul 2021 21:05:37 +0200 (CEST) Date: Mon, 19 Jul 2021 21:05:20 +0200 X-Report-Abuse-To: abuse@mxhotel.dk From: Sam Ravnborg To: Geert Uytterhoeven Subject: Re: [PATCH resend 2/5] video: fbdev: ssd1307fb: Simplify ssd1307fb_update_display() Message-ID: References: <20210714145804.2530727-1-geert@linux-m68k.org> <20210714145804.2530727-3-geert@linux-m68k.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210714145804.2530727-3-geert@linux-m68k.org> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fbdev@vger.kernel.org, David Airlie , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Geert, On Wed, Jul 14, 2021 at 04:58:01PM +0200, Geert Uytterhoeven wrote: > Simplify the nested loops to handle conversion from linear frame buffer > to ssd1307 page layout: > 1. Move last page handling one level up, as the value of "m" is the > same inside a page, > 2. array->data[] is filled linearly, so there is no need to > recalculate array_idx over and over again; a simple increment is > sufficient. > > Signed-off-by: Geert Uytterhoeven > --- > drivers/video/fbdev/ssd1307fb.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c > index e6b6263e3bef847f..6d7bd025bca1a175 100644 > --- a/drivers/video/fbdev/ssd1307fb.c > +++ b/drivers/video/fbdev/ssd1307fb.c > @@ -158,6 +158,7 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) > u8 *vmem = par->info->screen_buffer; > unsigned int line_length = par->info->fix.line_length; > unsigned int pages = DIV_ROUND_UP(par->height, 8); > + u32 array_idx = 0; > int ret, i, j, k; > > array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA); > @@ -194,19 +195,21 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) > */ > > for (i = 0; i < pages; i++) { > + int m = 8; > + > + /* Last page may be partial */ > + if (i + 1 == pages && par->height % 8) > + m = par->height % 8; > for (j = 0; j < par->width; j++) { > - int m = 8; > - u32 array_idx = i * par->width + j; > - array->data[array_idx] = 0; > - /* Last page may be partial */ > - if (i + 1 == pages && par->height % 8) > - m = par->height % 8; > + u8 data = 0; > + > for (k = 0; k < m; k++) { If the last page is partial then m will be less than 8 for all bytes in j = 0..par-width - but m should only be less than 8 for the last iteration of the loop. Do I miss something or is the code buggy? > u8 byte = vmem[(8 * i + k) * line_length + > j / 8]; > u8 bit = (byte >> (j % 8)) & 1; > - array->data[array_idx] |= bit << k; > + data |= bit << k; > } > + array->data[array_idx++] = data; > } > } Sam