From patchwork Mon Sep 19 17:17:38 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Keeping X-Patchwork-Id: 9340147 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7E6836077A for ; Mon, 19 Sep 2016 17:30:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 71E6B290C1 for ; Mon, 19 Sep 2016 17:30:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 66AA72933B; Mon, 19 Sep 2016 17:30:47 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 01074290C1 for ; Mon, 19 Sep 2016 17:30:47 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 86FF96E53F; Mon, 19 Sep 2016 17:30:25 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from metanate.com (dougal.metanate.com [90.155.101.14]) by gabe.freedesktop.org (Postfix) with ESMTPS id CCFBF6E53F for ; Mon, 19 Sep 2016 17:30:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=simple/simple; d=metanate.com; s=stronger; h=References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From; bh=qOB6O9u+RPtAK/llqW4nWwb7ZpnH66G/tHOf+AqHHHo=; b=uhWsAJ3Aa8vP7uJv6P2fB7wOVwY3ZHA4CJzNxE8uvDmyLPJRsAE7nmyxUVwL2KHRqGmEHhZ2T23fuyAvpi/w/6n0mYKrcjMR6NY5lzViBZf3FQlSN1u3u7CjRMLLiuBMM5haRQ2NMW6MJLhIlJ0vsCBZ+PisW9gS2wCfpcoKoPDF/eglJ5uJyJ7tx9ER0IOc5yfvCOpzrc3vW5oqeeZaG6ULob8BJV8mxf5jBq/pqIjG2Hby1msMd7AGVCbcOd0Mc8ukUUzupPRJv+SDmEHOiivf3qyD2+H/ybojdpIF96C/OvM7E6wglffl9HsyLLSAwNjo5y5t8Ii0y00TnusLHA==; Received: from brian ([192.168.88.1] helo=leela.metanate.com) by shrek.metanate.com with esmtpsa (TLSv1.2:DHE-RSA-AES128-GCM-SHA256:128) (Exim 4.83_RC2) (envelope-from ) id 1bm2CY-00078x-Js; Mon, 19 Sep 2016 18:17:54 +0100 From: John Keeping To: Mark Yao Subject: [PATCH 21/27] drm/rockchip: dw-mipi-dsi: improve PLL configuration Date: Mon, 19 Sep 2016 18:17:38 +0100 Message-Id: <20160919171747.28512-29-john@metanate.com> X-Mailer: git-send-email 2.10.0.278.g4f427b1.dirty In-Reply-To: <20160919171747.28512-1-john@metanate.com> References: <20160919171747.28512-1-john@metanate.com> Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP The multiplication ratio for the PLL is required to be even due to the use of a "by 2 pre-scaler". Currently we are likely to end up with an odd multiplier even though there is an equivalent set of parameters with an even multiplier. For example, using the 324MHz bit rate with a reference clock of 24MHz we end up with M = 27, N = 2 whereas the example in the PHY databook gives M = 54, N = 4 for this bit rate and reference clock. By walking down through the available multiplier instead of up we are more likely to hit an even multiplier. With the above example we do now get M = 54, N = 4 as given by the databook. While doing this, change the loop limits to encode the actual limits on the divisor, which are: 40MHz >= (pllref / N) >= 5MHz Signed-off-by: John Keeping --- drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c index 911ddcbab00d..2b26a54972da 100644 --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c @@ -520,7 +520,7 @@ static int dw_mipi_dsi_get_lane_bps(struct dw_mipi_dsi *dsi, pllref = DIV_ROUND_UP(clk_get_rate(dsi->pllref_clk), USEC_PER_SEC); tmp = pllref; - for (i = 1; i < 6; i++) { + for (i = pllref / 5; i > (pllref / 40); i--) { pre = pllref / i; if ((tmp > (target_mbps % pre)) && (target_mbps / pre < 512)) { tmp = target_mbps % pre;