From patchwork Wed Apr 10 12:51:35 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Flavio Suligoi X-Patchwork-Id: 10893853 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0B3F114DB for ; Wed, 10 Apr 2019 12:54:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E572C289BE for ; Wed, 10 Apr 2019 12:54:50 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D9D67289C4; Wed, 10 Apr 2019 12:54:50 +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=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 8D1E6289BA for ; Wed, 10 Apr 2019 12:54:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=ue6ON37gFLavXg0NXMTUiyXD6s//BCod/XJrwRTSjds=; b=NGHMYEzUG2C7cQ o79fYQvoiKlJPUsTd6I+up+lNUBXiHTWdGvMvSrE5WqVfpceUIO3YtYQZqtWuiMR4PugiUoaCv66c M936P9Xzj02TskaLrlGN+9DoxvYzlbm+6xghYT0Z+90sd7EJiZ8JyPiV4dmRDAAcHnoX9j60++9jE 0dxguvU/NUR4j3nG8QR0yN/+1DLl6F3Q6c8dWanHnVUYJYQBsHEaikI4IujLETWhhQK5NO+qLFS7b B/wcTxkP17bzmol/mpChcJUXHwX+eve3tQotXoT5uJITHkYvTwGwExJJf++KddOsGePbsxg0H9UcU D8LKMFsde7A5UvQYR4iQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hECkX-0006TY-6v; Wed, 10 Apr 2019 12:54:45 +0000 Received: from smtp.asem.it ([151.1.184.197]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hECkU-0006ST-1E for linux-arm-kernel@lists.infradead.org; Wed, 10 Apr 2019 12:54:43 +0000 Received: from webmail.asem.it by asem.it (smtp.asem.it) (SecurityGateway 5.5.0) with ESMTP id SG003804505.MSG for ; Wed, 10 Apr 2019 14:54:36 +0200S Received: from ASAS044.asem.intra (172.16.16.44) by ASAS044.asem.intra (172.16.16.44) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1261.35; Wed, 10 Apr 2019 14:54:35 +0200 Received: from flavio-x.asem.intra (172.16.17.208) by ASAS044.asem.intra (172.16.16.44) with Microsoft SMTP Server id 15.1.1261.35 via Frontend Transport; Wed, 10 Apr 2019 14:54:35 +0200 From: Flavio Suligoi To: Daniel Mack , Haojian Zhuang , Robert Jarzmik , Mark Brown Subject: [PATCH 1/2] spi: pxa2xx: fix SCR (divisor) calculation Date: Wed, 10 Apr 2019 14:51:35 +0200 Message-ID: <1554900696-28858-1-git-send-email-f.suligoi@asem.it> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-SGHeloLookup-Result: pass smtp.helo=webmail.asem.it (ip=172.16.16.44) X-SGSPF-Result: none (smtp.asem.it) X-SGOP-RefID: str=0001.0A0B0201.5CADE78C.0048, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 (_st=1 _vt=0 _iwf=0) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190410_055442_259858_145070B6 X-CRM114-Status: GOOD ( 12.93 ) 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: Flavio Suligoi , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-spi@vger.kernel.org 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 Calculate the divisor for the SCR (Serial Clock Rate), avoiding that the SSP transmission rate can be greater than the device rate. When the division between the SSP clock and the device rate generates a reminder, we have to increment by one the divisor. In this way the resulting SSP clock will never be greater than the device SPI max frequency. For example, with: - ssp_clk = 50 MHz - dev freq = 15 MHz without this patch the SSP clock will be greater than 15 MHz: - 25 MHz for PXA25x_SSP and CE4100_SSP - 16,56 MHz for the others Instead, with this patch, we have in both case an SSP clock of 12.5MHz, so the max rate of the SPI device clock is respected. Signed-off-by: Flavio Suligoi --- drivers/spi/spi-pxa2xx.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c index f7068cc..c9560a1 100644 --- a/drivers/spi/spi-pxa2xx.c +++ b/drivers/spi/spi-pxa2xx.c @@ -884,10 +884,15 @@ static unsigned int ssp_get_clk_div(struct driver_data *drv_data, int rate) rate = min_t(int, ssp_clk, rate); + /* + * Calculate the divisor for the SCR (Serial Clock Rate), avoiding + * that the SSP transmission rate can be greater than the device rate + */ if (ssp->type == PXA25x_SSP || ssp->type == CE4100_SSP) - return (ssp_clk / (2 * rate) - 1) & 0xff; + return (ssp_clk / (2 * rate) - 1 + + (ssp_clk % (2 * rate) ? 1 : 0)) & 0xff; else - return (ssp_clk / rate - 1) & 0xfff; + return (ssp_clk / rate - 1 + (ssp_clk % rate ? 1 : 0)) & 0xfff; } static unsigned int pxa2xx_ssp_get_clk_div(struct driver_data *drv_data,