From patchwork Sun Feb 24 16:23:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10828025 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 C2F46180E for ; Sun, 24 Feb 2019 16:23:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AF0CA2B08F for ; Sun, 24 Feb 2019 16:23:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A35E32B094; Sun, 24 Feb 2019 16:23:22 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3C9C52B08F for ; Sun, 24 Feb 2019 16:23:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727752AbfBXQXW (ORCPT ); Sun, 24 Feb 2019 11:23:22 -0500 Received: from 212-186-180-163.static.upcbusiness.at ([212.186.180.163]:48058 "EHLO cgate.sperl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728540AbfBXQXV (ORCPT ); Sun, 24 Feb 2019 11:23:21 -0500 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 7757584; Sun, 24 Feb 2019 16:23:15 +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 Cc: Martin Sperl Subject: [PATCH 2/3] spi: bcm2835: avoid 64 bit arithmetic and allow to configure polling limit Date: Sun, 24 Feb 2019 16:23:10 +0000 Message-Id: <20190224162311.23899-2-kernel@martin.sperl.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190224162311.23899-1-kernel@martin.sperl.org> References: <20190224162311.23899-1-kernel@martin.sperl.org> Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Martin Sperl In analogy to commit d704afffe65c ("spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc") avoid 64 bit calculations and make the polling interval configurable as a module parameter. Signed-off-by: Martin Sperl --- Note this patch requires the effective_speed_hz patch to be included --- drivers/spi/spi-bcm2835.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) -- 2.11.0 diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 0ccc6a2733c6..dcf922ca2603 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -38,6 +38,12 @@ #include #include +/* define polling limits */ +unsigned int polling_limit_us = 30; +module_param(polling_limit_us, uint, 0664); +MODULE_PARM_DESC(polling_limit_us, + "time in us to run a transfer in polling mode\n"); + /* SPI register offsets */ #define BCM2835_SPI_CS 0x00 #define BCM2835_SPI_FIFO 0x04 @@ -74,8 +80,6 @@ #define BCM2835_SPI_FIFO_SIZE 64 #define BCM2835_SPI_FIFO_SIZE_3_4 48 -#define BCM2835_SPI_POLLING_LIMIT_US 30 -#define BCM2835_SPI_POLLING_JIFFIES 2 #define BCM2835_SPI_DMA_MIN_LENGTH 96 #define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \ | SPI_NO_CS | SPI_3WIRE) @@ -784,8 +788,7 @@ static void bcm2835_dma_init(struct spi_master *master, struct device *dev) static int bcm2835_spi_transfer_one_poll(struct spi_master *master, struct spi_device *spi, struct spi_transfer *tfr, - u32 cs, - unsigned long long xfer_time_us) + u32 cs) { struct bcm2835_spi *bs = spi_master_get_devdata(master); unsigned long timeout; @@ -802,8 +805,8 @@ static int bcm2835_spi_transfer_one_poll(struct spi_master *master, */ bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE); - /* set the timeout */ - timeout = jiffies + BCM2835_SPI_POLLING_JIFFIES; + /* set the timeout to at least 2 jiffies */ + timeout = jiffies + 2 + HZ * polling_limit_us / 1000000; /* loop until finished the transfer */ while (bs->rx_len) { @@ -840,8 +843,7 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, struct spi_transfer *tfr) { struct bcm2835_spi *bs = spi_master_get_devdata(master); - unsigned long spi_hz, clk_hz, cdiv; - unsigned long long xfer_time_us; + unsigned long spi_hz, clk_hz, cdiv, hz_per_byte, byte_limit; u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); /* set clock */ @@ -882,16 +884,18 @@ 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, tfr->effective_speed_hz); + /* Calculate the estimated time in us the transfer runs. Note that + * there is 1 idle clocks cycles after each byte transferredo - so + * 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. + */ + hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0; + byte_limit = hz_per_byte ? tfr->effective_speed_hz / hz_per_byte : 1; /* for short requests run polling*/ - if (xfer_time_us <= BCM2835_SPI_POLLING_LIMIT_US) - return bcm2835_spi_transfer_one_poll(master, spi, tfr, - cs, xfer_time_us); + if (tfr->len < byte_limit) + return bcm2835_spi_transfer_one_poll(master, spi, tfr, cs); /* run in dma mode if conditions are right */ if (master->can_dma && bcm2835_spi_can_dma(master, spi, tfr))