From patchwork Sun Jan 29 13:24:37 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Keeping X-Patchwork-Id: 9543981 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 8B98A60415 for ; Sun, 29 Jan 2017 13:25:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7E60027F0B for ; Sun, 29 Jan 2017 13:25:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7320527F88; Sun, 29 Jan 2017 13:25:45 +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 1FEA327F0B for ; Sun, 29 Jan 2017 13:25:45 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 700666E10C; Sun, 29 Jan 2017 13:25:19 +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 B5C006E10C for ; Sun, 29 Jan 2017 13:25:15 +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=aOvB7Hz6ta7WD1YCQH0QJGbcINzNBHzQtL2HtfXn9/w=; b=HSBNQBIniffs80nD5qkYLAMMA6Hg4FgnOWUlWAB+9cKqEkEcEGw+Qs3ZhOR4J9RY6l+lpjieLSQXHkr8egEZPQBWiiTnwIT8JgwBoA2F3qyLNQxyfWAo1w/sFZPf+l0ElgpmkKbmOFBeOPi3e21uFMcpKD37nupRUR7NlHsCCuT+CbiW87vXZ5cH8EgRLMsjgI7/9LQGnbtcnhuJGwRntU7wo11X58NApTbBT15AhAVykSRaHoArRNMv01rO8ZuMmKDIEo+NtFrMNFQBklfuwMG8g9RgmYyH8VbQc47E4m3PJx+u5kEPw5KihgOECP0ymqP6rzPnERSK3GGbOX8iMA==; Received: from johnkeeping.plus.com ([81.174.171.191] helo=localhost.localdomain) by shrek.metanate.com with esmtpsa (TLSv1.2:DHE-RSA-AES128-GCM-SHA256:128) (Exim 4.83_RC2) (envelope-from ) id 1cXpTl-000362-9X; Sun, 29 Jan 2017 13:25:13 +0000 From: John Keeping To: Mark Yao Subject: [PATCH v3 17/24] drm/rockchip: dw-mipi-dsi: improve PLL configuration Date: Sun, 29 Jan 2017 13:24:37 +0000 Message-Id: <20170129132444.25251-18-john@metanate.com> X-Mailer: git-send-email 2.11.0.197.gb556de5.dirty In-Reply-To: <20170129132444.25251-1-john@metanate.com> References: <20170129132444.25251-1-john@metanate.com> Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, Chris Zhong , 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 Reviewed-by: Sean Paul --- Unchanged in v3 Unchanged in v2 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 85edf6dd2bac..dcb66a21e1f1 100644 --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c @@ -522,7 +522,7 @@ 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;