From patchwork Sun Feb 24 12:54:36 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10827895 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 954C06C2 for ; Sun, 24 Feb 2019 12:55:19 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 831E52B58C for ; Sun, 24 Feb 2019 12:55:19 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 76FDF2B5B0; Sun, 24 Feb 2019 12:55:19 +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 122512B58C for ; Sun, 24 Feb 2019 12:55:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728298AbfBXMzS (ORCPT ); Sun, 24 Feb 2019 07:55:18 -0500 Received: from 212-186-180-163.static.upcbusiness.at ([212.186.180.163]:47998 "EHLO cgate.sperl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725956AbfBXMzS (ORCPT ); Sun, 24 Feb 2019 07:55:18 -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 7757549; Sun, 24 Feb 2019 12:55:07 +0000 From: kernel@martin.sperl.org To: Mark Brown , Eric Anholt , Stefan Wahren , Hubert Denkmair , linux-spi@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org Cc: Martin Sperl Subject: [PATCH 5/9] spi: bcm2835aux: make the polling duration limits configurable Date: Sun, 24 Feb 2019 12:54:36 +0000 Message-Id: <20190224125440.16117-6-kernel@martin.sperl.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190224125440.16117-1-kernel@martin.sperl.org> References: <20190224125440.16117-1-kernel@martin.sperl.org> MIME-Version: 1.0 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 Under some circumstances the default 30 us polling limit is not optimal and may lead to long delays because we are waiting on the interrupt handler resulting in poor spi bus utilization. With this patch we have the possibility to influence this policy by making this limit configurable via a module parameters Signed-off-by: Martin Sperl --- Note that this patch relies on the effective_speed_hz patch for the driver to be applied! --- drivers/spi/spi-bcm2835aux.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) -- 2.11.0 diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c index 0a5f21eb3b99..af668cb6b38b 100644 --- a/drivers/spi/spi-bcm2835aux.c +++ b/drivers/spi/spi-bcm2835aux.c @@ -37,6 +37,12 @@ #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 defines * @@ -89,10 +95,6 @@ #define BCM2835_AUX_SPI_STAT_BUSY 0x00000040 #define BCM2835_AUX_SPI_STAT_BITCOUNT 0x0000003F -/* timeout values */ -#define BCM2835_AUX_SPI_POLLING_LIMIT_US 30 -#define BCM2835_AUX_SPI_POLLING_JIFFIES 2 - struct bcm2835aux_spi { void __iomem *regs; struct clk *clk; @@ -335,8 +337,8 @@ static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master, bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]); bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]); - /* set the timeout */ - timeout = jiffies + BCM2835_AUX_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) { @@ -381,7 +383,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master, struct spi_transfer *tfr) { struct bcm2835aux_spi *bs = spi_master_get_devdata(master); - unsigned long spi_hz, clk_hz, speed; + unsigned long spi_hz, clk_hz, speed, hz_per_byte, byte_limit; /* calculate the registers to handle * @@ -425,14 +427,15 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master, * of Hz per byte per polling limit. E.g., we can transfer 1 byte in * 30 µs per 300,000 Hz of bus clock. */ -#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_AUX_SPI_POLLING_LIMIT_US) + 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; + /* run in polling mode for short transfers */ - if (tfr->len < tfr->effective_speed_hz / HZ_PER_BYTE) + if (tfr->len < byte_limit) return bcm2835aux_spi_transfer_one_poll(master, spi, tfr); /* run in interrupt mode for all others */ return bcm2835aux_spi_transfer_one_irq(master, spi, tfr); -#undef HZ_PER_BYTE } static int bcm2835aux_spi_prepare_message(struct spi_master *master,