From patchwork Sat Jan 21 16:31:21 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Keeping X-Patchwork-Id: 9530455 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 F2A1B6020B for ; Sat, 21 Jan 2017 16:35:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E4F1528119 for ; Sat, 21 Jan 2017 16:35:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DA0102842E; Sat, 21 Jan 2017 16:35:42 +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=-1.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, T_DKIM_INVALID autolearn=no version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id A795628119 for ; Sat, 21 Jan 2017 16:35:42 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1cUydh-0002st-Av; Sat, 21 Jan 2017 16:35:41 +0000 Received: from dougal.metanate.com ([90.155.101.14] helo=metanate.com) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1cUyaa-0005Vx-4s; Sat, 21 Jan 2017 16:32:38 +0000 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=+daV3rsqorsthy9cSmsJ2sqWAg6U1VuuN8HSxAF1Z6A=; b=WISdOTye8y7eKOgU+zlkL4i8QAV+7MG5to1d1hzIfN7ibIAi5D47WgcNgJb49R32uzUn8RjpoTvFlkNa3PdJswAhOdIBi2PCZKZXJngFoQAmSR+qoQRuZS2OC4J9liIipYVhm3fVa8HO7WG27v2dphPYIV3bJUe/t9YD1q7rilYb2jvzt1XTT6WscrQYTKNNxU1P5Gq2QuLWXvri0wnKC4KQ5x/GERBsl5wr46nPY2njfYFcwAvMYBvobxz+GT5PC2flJE5MlIEkhj/cfdIwsGnBmpOw/2pyxgDALaf0Iv/6oyod7fWX/9/bM48ScgjrrMgei1FE6ar/mQ9P60vw7w==; 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 1cUya4-0004rJ-Av; Sat, 21 Jan 2017 16:31:56 +0000 From: John Keeping To: Mark Yao Subject: [PATCH v2 19/26] drm/rockchip: dw-mipi-dsi: improve PLL configuration Date: Sat, 21 Jan 2017 16:31:21 +0000 Message-Id: <20170121163128.22240-20-john@metanate.com> X-Mailer: git-send-email 2.11.0.197.gb556de5.dirty In-Reply-To: <20170121163128.22240-1-john@metanate.com> References: <20170121163128.22240-1-john@metanate.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20170121_083228_505330_6533CC76 X-CRM114-Status: GOOD ( 10.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, John Keeping , Chris Zhong , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org 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 --- 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 12432e41971b..f2320cf1366c 100644 --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c @@ -519,7 +519,7 @@ 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;