From patchwork Tue Apr 23 20:15:08 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10913709 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 85762112C for ; Tue, 23 Apr 2019 20:15:37 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7872E2863F for ; Tue, 23 Apr 2019 20:15:37 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6CECC28918; Tue, 23 Apr 2019 20:15:37 +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 19FC02863F for ; Tue, 23 Apr 2019 20:15:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726029AbfDWUPg (ORCPT ); Tue, 23 Apr 2019 16:15:36 -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 S1725956AbfDWUPg (ORCPT ); Tue, 23 Apr 2019 16:15:36 -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 7763603; 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 Cc: Martin Sperl Subject: [PATCH V2 1/6] spi: bcm2835: bcm2835_spi_transfer_one_poll remove unnecessary argument Date: Tue, 23 Apr 2019 20:15:08 +0000 Message-Id: <20190423201513.8073-2-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 Remove the unnecessary argument of xfer_time_us when calling bcm2835_spi_transfer_one_poll. Signed-off-by: Martin Sperl Changelog: V1 -> V2: applied feedback by Stefan Wahren reorganized patchset added extra rational, descriptions --- drivers/spi/spi-bcm2835.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) -- 2.11.0 diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 35aebdfd3b4e..ef7f8dc9f18e 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -725,8 +725,7 @@ 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; @@ -827,8 +826,7 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, /* 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); + 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)) 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: 10913711 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 8FE941515 for ; Tue, 23 Apr 2019 20:15:39 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7DE292863F for ; Tue, 23 Apr 2019 20:15:39 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7C4A9288FA; Tue, 23 Apr 2019 20:15:39 +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 282A52863F for ; Tue, 23 Apr 2019 20:15:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725945AbfDWUPi (ORCPT ); Tue, 23 Apr 2019 16:15:38 -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 S1725956AbfDWUPi (ORCPT ); Tue, 23 Apr 2019 16:15:38 -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 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 Cc: Martin Sperl 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> 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 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 */ From patchwork Tue Apr 23 20:15:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10913713 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 104021515 for ; Tue, 23 Apr 2019 20:15:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 02D56288EE for ; Tue, 23 Apr 2019 20:15:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 00F0C288FA; Tue, 23 Apr 2019 20:15:40 +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 AF58B288EE for ; Tue, 23 Apr 2019 20:15:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726136AbfDWUPk (ORCPT ); Tue, 23 Apr 2019 16:15:40 -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 S1725956AbfDWUPk (ORCPT ); Tue, 23 Apr 2019 16:15:40 -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 7763605; 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 3/6] spi: bcm2835: added comment about different bus behaviour of DMA mode Date: Tue, 23 Apr 2019 20:15:10 +0000 Message-Id: <20190423201513.8073-4-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 The DMA mode behaves slightly different than polling or interrupt driven mode, so just document the fact Signed-off-by: Martin Sperl Changelog: V1 -> V2: applied feedback by Stefan Wahren new in V2 --- drivers/spi/spi-bcm2835.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) -- 2.11.0 diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index a64bfa8e0710..3140d952c03a 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -828,7 +828,10 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, 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 */ + /* run in dma mode if conditions are right + * Note that unlike poll or interrupt mode DMA mode does not have + * this 1 idle clock cycle pattern but runs the spi clock without gaps + */ if (master->can_dma && bcm2835_spi_can_dma(master, spi, tfr)) return bcm2835_spi_transfer_one_dma(master, spi, tfr, cs); 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 From patchwork Tue Apr 23 20:15:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10913717 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 198D61515 for ; Tue, 23 Apr 2019 20:15:44 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0C258286F1 for ; Tue, 23 Apr 2019 20:15:44 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 00C05288E8; Tue, 23 Apr 2019 20:15:43 +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 9645E286F1 for ; Tue, 23 Apr 2019 20:15:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726339AbfDWUPn (ORCPT ); Tue, 23 Apr 2019 16:15:43 -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 S1725956AbfDWUPn (ORCPT ); Tue, 23 Apr 2019 16:15:43 -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 7763607; 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 5/6] spi: bcm2835: make the lower limit for dma mode configurable Date: Tue, 23 Apr 2019 20:15:12 +0000 Message-Id: <20190423201513.8073-6-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 96 byte limit is not optimal. The polling and interrupt mode of the spi-bcm2835 controller exhibit a 1 idle clock cycle which is missing when using DMA. So when transferring a longer spi_transfer to some low spec MCU devices without SPI FIFOs like a ATMega it means that the SPI has to get reduced by a factor of 2 or more when using DMA mode compared to using PIO modes to give the MCU enough time to handle the incoming spi byte and prepare the next byte to get delivered - these extra 4+ CPU cycles that the idle spi clock is providing allows bigger transfers to work at faster speeds (assuming highly optimized MCU code). So forcing the transfer to use PIO mode to geth this behaviour for longer transfers is of advantage. The oposite is true when (ab)using the spi MOSI line alone to control a WS2812B RGB LED stripe, where the DMA mode makes it possible to use the MOSI lines alone (with correct encoding) to control the LED. So both extremes have there use cases and with this patch we allow to control the policy on a controller wide basis. Right now we only allow to control the limit on a controller wide basis, but in the future it may be possible to configure this on a per spi_device basis. Signed-off-by: Martin Sperl --- drivers/spi/spi-bcm2835.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 2d702db8689c..755e1e6d2252 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -73,7 +73,6 @@ #define BCM2835_SPI_FIFO_SIZE 64 #define BCM2835_SPI_FIFO_SIZE_3_4 48 -#define BCM2835_SPI_DMA_MIN_LENGTH 96 #define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \ | SPI_NO_CS | SPI_3WIRE) @@ -85,6 +84,12 @@ module_param(polling_limit_us, uint, 0664); MODULE_PARM_DESC(polling_limit_us, "time in us to run a transfer in polling mode\n"); +/* define minimum transfer length for which we may use DMA */ +unsigned int dma_min_bytes_limit = 96; +module_param(dma_min_bytes_limit, uint, 0664); +MODULE_PARM_DESC(dma_min_bytes_limit, + "minimum number of bytes to run a transfer in dma mode - 0 disables dma-mode completely\n"); + /** * struct bcm2835_spi - BCM2835 SPI controller * @regs: base address of register map @@ -631,7 +636,7 @@ static bool bcm2835_spi_can_dma(struct spi_master *master, struct spi_transfer *tfr) { /* we start DMA efforts only on bigger transfers */ - if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH) + if (!dma_min_bytes_limit || tfr->len < dma_min_bytes_limit) return false; /* BCM2835_SPI_DLEN has defined a max transfer size as From patchwork Tue Apr 23 20:15:13 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10913719 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 C6EFA1515 for ; Tue, 23 Apr 2019 20:15:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B982E288EE for ; Tue, 23 Apr 2019 20:15:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B7EE3288FA; Tue, 23 Apr 2019 20:15:45 +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 41B47288EE for ; Tue, 23 Apr 2019 20:15:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726342AbfDWUPp (ORCPT ); Tue, 23 Apr 2019 16:15:45 -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 S1725956AbfDWUPo (ORCPT ); Tue, 23 Apr 2019 16:15:44 -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 7763609; 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 6/6] spi: bcm2835: add driver stats to debugfs Date: Tue, 23 Apr 2019 20:15:13 +0000 Message-Id: <20190423201513.8073-7-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 To estimate efficiency add statistics on transfer types (polling, interrupt and dma) used to debugfs. Signed-off-by: Martin Sperl Changelog: V1 -> V2: applied feedback by Stefan Wahren reorganized patchset added extra rational, descriptions fixed compile issue when CONFIG_DEBUG_FS is unset --- drivers/spi/spi-bcm2835.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) -- 2.11.0 diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 755e1e6d2252..83a67eb76325 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -22,6 +22,7 @@ #include #include +#include #include #include #include @@ -106,6 +107,15 @@ MODULE_PARM_DESC(dma_min_bytes_limit, * length is not a multiple of 4 (to overcome hardware limitation) * @tx_spillover: whether @tx_prologue spills over to second TX sglist entry * @dma_pending: whether a DMA transfer is in progress + * @debugfs_dir: the debugfs directory - neede to remove debugfs when + * unloading the module + * @count_transfer_polling: count of how often polling mode is used + * @count_transfer_irq: count of how often interrupt mode is used + * @count_transfer_irq_after_polling: count of how often we fall back to + * interrupt mode after starting in polling mode. + * These are counted as well in @count_transfer_polling and + * @count_transfer_irq + * @count_transfer_dma: count how often dma mode is used */ struct bcm2835_spi { void __iomem *regs; @@ -120,8 +130,55 @@ struct bcm2835_spi { int rx_prologue; unsigned int tx_spillover; unsigned int dma_pending; + + struct dentry *debugfs_dir; + u64 count_transfer_polling; + u64 count_transfer_irq; + u64 count_transfer_irq_after_polling; + u64 count_transfer_dma; }; +#if defined(CONFIG_DEBUG_FS) +static void bcm2835_debugfs_create(struct bcm2835_spi *bs, + const char *dname) +{ + char name[64]; + struct dentry *dir; + + /* get full name */ + snprintf(name, sizeof(name), "spi-bcm2835-%s", dname); + + /* the base directory */ + dir = debugfs_create_dir(name, NULL); + bs->debugfs_dir = dir; + + /* the counters */ + debugfs_create_u64("count_transfer_polling", 0444, dir, + &bs->count_transfer_polling); + debugfs_create_u64("count_transfer_irq", 0444, dir, + &bs->count_transfer_irq); + debugfs_create_u64("count_transfer_irq_after_polling", 0444, dir, + &bs->count_transfer_irq_after_polling); + debugfs_create_u64("count_transfer_dma", 0444, dir, + &bs->count_transfer_dma); +} + +static void bcm2835_debugfs_remove(struct bcm2835_spi *bs) +{ + debugfs_remove_recursive(bs->debugfs_dir); + bs->debugfs_dir = NULL; +} +#else +static void bcm2835_debugfs_create(struct bcm2835_spi *bs, + const char *dname) +{ +} + +static void bcm2835_debugfs_remove(struct bcm2835_spi *bs) +{ +} +#endif /* CONFIG_DEBUG_FS */ + static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg) { return readl(bs->regs + reg); @@ -325,6 +382,9 @@ static int bcm2835_spi_transfer_one_irq(struct spi_master *master, { struct bcm2835_spi *bs = spi_master_get_devdata(master); + /* update usage statistics */ + bs->count_transfer_irq++; + /* * Enable HW block, but with interrupts still disabled. * Otherwise the empty TX FIFO would immediately trigger an interrupt. @@ -583,6 +643,9 @@ static int bcm2835_spi_transfer_one_dma(struct spi_master *master, struct bcm2835_spi *bs = spi_master_get_devdata(master); int ret; + /* update usage statistics */ + bs->count_transfer_dma++; + /* * Transfer first few bytes without DMA if length of first TX or RX * sglist entry is not a multiple of 4 bytes (hardware limitation). @@ -739,6 +802,9 @@ static int bcm2835_spi_transfer_one_poll(struct spi_master *master, struct bcm2835_spi *bs = spi_master_get_devdata(master); unsigned long timeout; + /* update usage statistics */ + bs->count_transfer_polling++; + /* enable HW block without interrupts */ bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA); @@ -768,6 +834,10 @@ static int bcm2835_spi_transfer_one_poll(struct spi_master *master, jiffies - timeout, bs->tx_len, bs->rx_len); /* fall back to interrupt mode */ + + /* update usage statistics */ + bs->count_transfer_irq_after_polling++; + return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs, false); } @@ -1004,6 +1074,8 @@ static int bcm2835_spi_probe(struct platform_device *pdev) goto out_clk_disable; } + bcm2835_debugfs_create(bs, dev_name(&pdev->dev)); + return 0; out_clk_disable: @@ -1018,6 +1090,8 @@ static int bcm2835_spi_remove(struct platform_device *pdev) struct spi_master *master = platform_get_drvdata(pdev); struct bcm2835_spi *bs = spi_master_get_devdata(master); + bcm2835_debugfs_remove(bs); + /* Clear FIFOs, and disable the HW block */ bcm2835_wr(bs, BCM2835_SPI_CS, BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);