From patchwork Tue Apr 23 20:15:11 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10913715 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 D14F9112C for ; Tue, 23 Apr 2019 20:15:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C2CE428918 for ; Tue, 23 Apr 2019 20:15:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B720328915; Tue, 23 Apr 2019 20:15:42 +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 5C73128915 for ; Tue, 23 Apr 2019 20:15:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726157AbfDWUPm (ORCPT ); Tue, 23 Apr 2019 16:15:42 -0400 Received: from 212-186-180-163.static.upcbusiness.at ([212.186.180.163]:33362 "EHLO cgate.sperl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725956AbfDWUPm (ORCPT ); Tue, 23 Apr 2019 16:15:42 -0400 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 7763606; Tue, 23 Apr 2019 20:15:33 +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 V2 4/6] spi: bcm2835: make the polling duration limits configurable Date: Tue, 23 Apr 2019 20:15:11 +0000 Message-Id: <20190423201513.8073-5-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> 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 an interrupt. with this patch we have the possibility to influence this policy. So make this limit (in us) configurable via a module parameters (but also modifyable via /sys/modules/...) This replicates similar code found in 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 | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) -- 2.11.0 diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 3140d952c03a..2d702db8689c 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -73,14 +73,18 @@ #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) #define DRV_NAME "spi-bcm2835" +/* 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"); + /** * struct bcm2835_spi - BCM2835 SPI controller * @regs: base address of register map @@ -739,8 +743,8 @@ 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) { @@ -775,8 +779,8 @@ 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 spi_used_hz; + unsigned long spi_hz, clk_hz, cdiv, spi_used_hz; + unsigned long hz_per_byte, byte_limit; u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); /* set clock */ @@ -823,9 +827,11 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, * 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) + hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0; + byte_limit = hz_per_byte ? spi_used_hz / hz_per_byte : 1; + /* run in polling mode for short transfers */ - if (tfr->len < spi_used_hz / HZ_PER_BYTE) + if (tfr->len < byte_limit) return bcm2835_spi_transfer_one_poll(master, spi, tfr, cs); /* run in dma mode if conditions are right