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=-13.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 671B2C433E3 for ; Mon, 20 Jul 2020 16:40:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4091C206E9 for ; Mon, 20 Jul 2020 16:40:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595263236; bh=6tjy0WJNNWDwPU1CTmUUpnIdSjE0etRp+xsOx3xzA50=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Nx8MtzdnjuXgCCxKV/ZFyJtZUbtm47bUTePBvfOs+W2kGa2jn8YAtH7jN4/89GAxO eVwzvb+UMrcYWE0oyvqO7CJF/uxCGLTouGefQhLXGNIqgLt+Z72V7Be8w+ZxD0bYQu sEOIF4Uc7uH8nroa84n/IAhqvlJaaQR8dVpsEj18= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388826AbgGTQkd (ORCPT ); Mon, 20 Jul 2020 12:40:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:42430 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730752AbgGTPrT (ORCPT ); Mon, 20 Jul 2020 11:47:19 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5AFFF2065E; Mon, 20 Jul 2020 15:47:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595260038; bh=6tjy0WJNNWDwPU1CTmUUpnIdSjE0etRp+xsOx3xzA50=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fBkUVgfWZg5CsRGWewMY0WnmA681nSmZpj0Q1lI9uS63HXtacD1OzBeKiMMWae6Ca wHSOZehVDM2TxH7QUCX6EPIp0seSrshDOvqZdj94UHQIE1GKYUPtLSFQZQjVzuOJd5 nOKZf0B5/NBORQrVG4YvsztDe3kcVNoefg9nMgk4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marc Kleine-Budde , Maxime Ripard , Mark Brown , Sasha Levin Subject: [PATCH 4.14 083/125] spi: spi-sun6i: sun6i_spi_transfer_one(): fix setting of clock rate Date: Mon, 20 Jul 2020 17:37:02 +0200 Message-Id: <20200720152807.029149590@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200720152802.929969555@linuxfoundation.org> References: <20200720152802.929969555@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Marc Kleine-Budde [ Upstream commit ed7815db70d17b1741883f2da8e1d80bc2efe517 ] A SPI transfer defines the _maximum_ speed of the SPI transfer. However the driver doesn't take into account that the clock divider is always rounded down (due to integer arithmetics). This results in a too high clock rate for the SPI transfer. E.g.: with a mclk_rate of 24 MHz and a SPI transfer speed of 10 MHz, the original code calculates a reg of "0", which results in a effective divider of "2" and a 12 MHz clock for the SPI transfer. This patch fixes the issue by using DIV_ROUND_UP() instead of a plain integer division. While there simplify the divider calculation for the CDR1 case, use order_base_2() instead of two ilog2() calculations. Fixes: 3558fe900e8a ("spi: sunxi: Add Allwinner A31 SPI controller driver") Signed-off-by: Marc Kleine-Budde Acked-by: Maxime Ripard Link: https://lore.kernel.org/r/20200706143443.9855-2-mkl@pengutronix.de Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- drivers/spi/spi-sun6i.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c index 8533f4edd00af..21a22d42818c8 100644 --- a/drivers/spi/spi-sun6i.c +++ b/drivers/spi/spi-sun6i.c @@ -202,7 +202,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master, struct spi_transfer *tfr) { struct sun6i_spi *sspi = spi_master_get_devdata(master); - unsigned int mclk_rate, div, timeout; + unsigned int mclk_rate, div, div_cdr1, div_cdr2, timeout; unsigned int start, end, tx_time; unsigned int trig_level; unsigned int tx_len = 0; @@ -291,14 +291,12 @@ static int sun6i_spi_transfer_one(struct spi_master *master, * First try CDR2, and if we can't reach the expected * frequency, fall back to CDR1. */ - div = mclk_rate / (2 * tfr->speed_hz); - if (div <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) { - if (div > 0) - div--; - - reg = SUN6I_CLK_CTL_CDR2(div) | SUN6I_CLK_CTL_DRS; + div_cdr1 = DIV_ROUND_UP(mclk_rate, tfr->speed_hz); + div_cdr2 = DIV_ROUND_UP(div_cdr1, 2); + if (div_cdr2 <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) { + reg = SUN6I_CLK_CTL_CDR2(div_cdr2 - 1) | SUN6I_CLK_CTL_DRS; } else { - div = ilog2(mclk_rate) - ilog2(tfr->speed_hz); + div = min(SUN6I_CLK_CTL_CDR1_MASK, order_base_2(div_cdr1)); reg = SUN6I_CLK_CTL_CDR1(div); } -- 2.25.1