From patchwork Wed Aug 20 12:41:04 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jon Medhurst (Tixy)" X-Patchwork-Id: 4750761 Return-Path: X-Original-To: patchwork-linux-fbdev@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 8CD9AC0338 for ; Wed, 20 Aug 2014 12:41:12 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id AC1D22015E for ; Wed, 20 Aug 2014 12:41:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD8A0200EC for ; Wed, 20 Aug 2014 12:41:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752384AbaHTMlJ (ORCPT ); Wed, 20 Aug 2014 08:41:09 -0400 Received: from smarthost01d.mail.zen.net.uk ([212.23.1.7]:54065 "EHLO smarthost01d.mail.zen.net.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752193AbaHTMlJ (ORCPT ); Wed, 20 Aug 2014 08:41:09 -0400 Received: from [82.69.122.217] (helo=linaro1) by smarthost01d.mail.zen.net.uk with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.80) (envelope-from ) id 1XK5CK-0001cQ-QB; Wed, 20 Aug 2014 12:41:04 +0000 Message-ID: <1408538464.3858.43.camel@linaro1.home> Subject: [PATCH v2] video: ARM CLCD: Fix calculation of bits-per-pixel From: "Jon Medhurst (Tixy)" To: Russell King - ARM Linux , Tomi Valkeinen , Jean-Christophe Plagniol-Villard Cc: linux-fbdev@vger.kernel.org, Pawel Moll , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Date: Wed, 20 Aug 2014 13:41:04 +0100 X-Mailer: Evolution 3.12.2-1+b1 Mime-Version: 1.0 X-Originating-smarthost01d-IP: [82.69.122.217] Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Spam-Status: No, score=-7.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If the device-tree specifies a max-memory-bandwidth property then the CLCD driver uses that to calculate the bits-per-pixel supported, however, this calculation is faulty for two reasons. 1. It doesn't ensure that the result is a sane value, i.e. a power of 2 and <= 32 as the rest of the code assumes. 2. It uses the displayed resolution and calculates the average bandwidth across the whole frame. It should instead calculate the peak bandwidth based on the pixel clock. This patch fixes both the above. Signed-off-by: Jon Medhurst Acked-by: Pawel Moll --- Changes since v1: - Changed formula for calculating bits per pixel - Changed commit message and subject, was: "video: ARM CLCD: Ensure bits-per-pixel is a power of 2 and <= 32" drivers/video/fbdev/amba-clcd.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/drivers/video/fbdev/amba-clcd.c b/drivers/video/fbdev/amba-clcd.c index beadd3e..a7b6217 100644 --- a/drivers/video/fbdev/amba-clcd.c +++ b/drivers/video/fbdev/amba-clcd.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include @@ -650,6 +651,7 @@ static int clcdfb_of_init_display(struct clcd_fb *fb) { struct device_node *endpoint; int err; + unsigned int bpp; u32 max_bandwidth; u32 tft_r0b0g0[3]; @@ -667,11 +669,22 @@ static int clcdfb_of_init_display(struct clcd_fb *fb) err = of_property_read_u32(fb->dev->dev.of_node, "max-memory-bandwidth", &max_bandwidth); - if (!err) - fb->panel->bpp = 8 * max_bandwidth / (fb->panel->mode.xres * - fb->panel->mode.yres * fb->panel->mode.refresh); - else - fb->panel->bpp = 32; + if (!err) { + /* + * max_bandwidth is in bytes per second and pixclock in + * pico-seconds, so the maximum allowed bits per pixel is + * 8 * max_bandwidth / (PICOS2KHZ(pixclock) * 1000) + * Rearrange this calculation to avoid overflow and then ensure + * result is a valid format. + */ + bpp = max_bandwidth / (1000 / 8) + / PICOS2KHZ(fb->panel->mode.pixclock); + bpp = rounddown_pow_of_two(bpp); + if (bpp > 32) + bpp = 32; + } else + bpp = 32; + fb->panel->bpp = bpp; #ifdef CONFIG_CPU_BIG_ENDIAN fb->panel->cntl |= CNTL_BEBO;