From patchwork Wed Aug 19 12:59:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Geert Uytterhoeven X-Patchwork-Id: 11724097 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B5A5A913 for ; Wed, 19 Aug 2020 13:07:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B8ED207BB for ; Wed, 19 Aug 2020 13:07:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728591AbgHSNHU (ORCPT ); Wed, 19 Aug 2020 09:07:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728558AbgHSNAO (ORCPT ); Wed, 19 Aug 2020 09:00:14 -0400 Received: from xavier.telenet-ops.be (xavier.telenet-ops.be [IPv6:2a02:1800:120:4::f00:14]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF160C06135A for ; Wed, 19 Aug 2020 05:59:15 -0700 (PDT) Received: from ramsan ([84.195.186.194]) by xavier.telenet-ops.be with bizsmtp id HQz6230034C55Sk01Qz6d4; Wed, 19 Aug 2020 14:59:06 +0200 Received: from rox.of.borg ([192.168.97.57]) by ramsan with esmtp (Exim 4.90_1) (envelope-from ) id 1k8NgI-0002bi-1P; Wed, 19 Aug 2020 14:59:06 +0200 Received: from geert by rox.of.borg with local (Exim 4.90_1) (envelope-from ) id 1k8NgI-0005Sg-0U; Wed, 19 Aug 2020 14:59:06 +0200 From: Geert Uytterhoeven To: Mark Brown Cc: Chris Brandt , linux-spi@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-sh@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH v2 3/7] spi: rspi: Increase bit rate accuracy on RZ/A Date: Wed, 19 Aug 2020 14:59:00 +0200 Message-Id: <20200819125904.20938-4-geert+renesas@glider.be> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200819125904.20938-1-geert+renesas@glider.be> References: <20200819125904.20938-1-geert+renesas@glider.be> Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org rspi_rz_set_config_register() favors high values of "brdv" over high values of "spbr". As "brdv" is not a plain divider, but controls a power-of-two divider, this may cause the selection of non-optimal divider values. E.g. on RSK+RZA1, when 3.8 MHz is requested, the actual configured bit rate is 2.08 MHz (spbr = 1, brdv = 3), while 3.7 MHz would be possible (spbr = 8, brdv = 0). Fix this by only resorting to higher "brdv" values when really needed. This makes the driver always pick optimal divider values on RZ/A. Signed-off-by: Geert Uytterhoeven --- v2: - No changes. drivers/spi/spi-rspi.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c index 450a42ec2141a895..ad4ac867170b101a 100644 --- a/drivers/spi/spi-rspi.c +++ b/drivers/spi/spi-rspi.c @@ -298,15 +298,13 @@ static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size) rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR); clksrc = clk_get_rate(rspi->clk); - while (brdv < 3) { - if (rspi->speed_hz >= clksrc/4) /* 4=(CLK/2)/2 */ - break; + spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1; + while (spbr > 255 && brdv < 3) { brdv++; - clksrc /= 2; + spbr = DIV_ROUND_UP(spbr + 1, 2) - 1; } /* Sets transfer bit rate */ - spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1; rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR); rspi->spcmd |= SPCMD_BRDV(brdv);