From patchwork Tue Apr 23 20:15:09 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10913725 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 1272C1515 for ; Tue, 23 Apr 2019 20:16:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 041D925826 for ; Tue, 23 Apr 2019 20:16:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 025A1288FA; Tue, 23 Apr 2019 20:16:23 +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=unavailable 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 97F7B25826 for ; Tue, 23 Apr 2019 20:16:23 +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:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To: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:List-Owner; bh=sKemnCsvRUfq6fYQqx7UYho5fc448ktdNMvKQVpdXjk=; b=tPyR/HQ+icLoh42O6OxhpSJDhl TSdJegwXnKFDGMXh/dir8x79D2TyROFbk1XezIPlffct8GC4XgRsGG1l43WrK1wFitEGhX29hGQAh TrXJXb1mknwdwUegUv9gRand6upyLO8GIiod0ZzAGs/IYEGpRwjWeq0bEHltOuk79YT1m5i3H6Hbw y627L6CWnugeex4QI1mwBCntvjxtnxnh0UpBs1d4d6Zov9QrK+XEXnud2JjgCfIFYEIv9F5tXXM/q 3Q1aY8ksMrkPQkK15fIQyedI3Uc9ZNieWIAMx9Ua27tN/f1BpIXcridc0eHbqMxhT2U5ZfnJPQ/p4 nxEz6ZPw==; 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 1hJ1pw-0000B9-OU; Tue, 23 Apr 2019 20:16:16 +0000 Received: from 212-186-180-163.static.upcbusiness.at ([212.186.180.163] helo=cgate.sperl.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJ1pZ-00086p-90; Tue, 23 Apr 2019 20:15:56 +0000 Received: from hc1.intern.sperl.org (account martin@sperl.org [10.10.10.59] verified) by sperl.org (CommuniGate Pro SMTP 6.2.1 _community_) with ESMTPSA id 7763604; Tue, 23 Apr 2019 20:15:32 +0000 From: kernel@martin.sperl.org To: Mark Brown , Eric Anholt , Stefan Wahren , linux-spi@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH V2 2/6] spi: bcm2835: Avoid 64-bit arithmetic in xfer len calc Date: Tue, 23 Apr 2019 20:15:09 +0000 Message-Id: <20190423201513.8073-3-kernel@martin.sperl.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190423201513.8073-1-kernel@martin.sperl.org> References: <20190423201513.8073-1-kernel@martin.sperl.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190423_131553_817863_A05B5528 X-CRM114-Status: UNSURE ( 8.27 ) X-CRM114-Notice: Please train this message. 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: Martin Sperl 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 From: Martin Sperl Avoid 64 bit aritmetics when deciding if we need to use polling or not This replicates: commit d704afffe65c ("spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc") from spi-bcm2835aux Signed-off-by: Martin Sperl Changelog: V1 -> V2: applied feedback by Stefan Wahren reorganized patchset added extra rational, descriptions --- drivers/spi/spi-bcm2835.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) -- 2.11.0 diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index ef7f8dc9f18e..a64bfa8e0710 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -777,7 +777,6 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, struct bcm2835_spi *bs = spi_master_get_devdata(master); unsigned long spi_hz, clk_hz, cdiv; unsigned long spi_used_hz; - unsigned long long xfer_time_us; u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); /* set clock */ @@ -818,14 +817,15 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, bs->tx_len = tfr->len; bs->rx_len = tfr->len; - /* calculate the estimated time in us the transfer runs */ - xfer_time_us = (unsigned long long)tfr->len - * 9 /* clocks/byte - SPI-HW waits 1 clock after each byte */ - * 1000000; - do_div(xfer_time_us, spi_used_hz); - - /* for short requests run polling*/ - if (xfer_time_us <= BCM2835_SPI_POLLING_LIMIT_US) + /* Calculate the estimated time in us the transfer runs. Note that + * there is 1 idle clocks cycles after each byte getting transferred + * so we have 9 cycles/byte. This is used to find the number of Hz + * per byte per polling limit. E.g., we can transfer 1 byte in 30 us + * per 300,000 Hz of bus clock. + */ +#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_SPI_POLLING_LIMIT_US) + /* run in polling mode for short transfers */ + if (tfr->len < spi_used_hz / HZ_PER_BYTE) return bcm2835_spi_transfer_one_poll(master, spi, tfr, cs); /* run in dma mode if conditions are right */