From patchwork Sat Feb 23 08:49:48 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Sperl X-Patchwork-Id: 10827347 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 8BE141390 for ; Sat, 23 Feb 2019 08:50:11 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 73BAB2F9F1 for ; Sat, 23 Feb 2019 08:50:11 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6809F30CCE; Sat, 23 Feb 2019 08:50:11 +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 ED3642F9F1 for ; Sat, 23 Feb 2019 08:50:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726269AbfBWIuK (ORCPT ); Sat, 23 Feb 2019 03:50:10 -0500 Received: from 212-186-180-163.static.upcbusiness.at ([212.186.180.163]:47824 "EHLO cgate.sperl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726043AbfBWIuK (ORCPT ); Sat, 23 Feb 2019 03:50:10 -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 7757391; Sat, 23 Feb 2019 08:50:05 +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 1/5] spi: core: allow defining time that cs is deasserted Date: Sat, 23 Feb 2019 08:49:48 +0000 Message-Id: <20190223084952.14758-2-kernel@martin.sperl.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190223084952.14758-1-kernel@martin.sperl.org> References: <20190223084952.14758-1-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 For some SPI devices that support speed_hz > 1MHz the default 10 us delay when cs_change = 1 is typically way to long and may result in poor spi bus utilization. This patch makes it possible to control the delay at micro or nano second resolution on a per spi_transfer basis. It even allows an "as fast as possible" mode with: xfer.cs_change_delay_unit = SPI_DELAY_UNIT_NSECS; xfer.cs_change_delay = 0; The delay code is shared between delay_usecs and cs_change_delay for consistency and reuse, so in the future this change_delay_unit could also apply to delay_usec as well. Note that on slower SOCs/CPU actually reaching ns deasserts on cs is not realistic as the gpio overhead alone (without any delays added ) may already leave cs deasserted for more than 1us - at least on a raspberry pi. But at the very least this way we can keep it as short as possible. Signed-off-by: Martin Sperl --- drivers/spi/spi.c | 59 ++++++++++++++++++++++++++++++++++++++++--------- include/linux/spi/spi.h | 7 ++++++ 2 files changed, 56 insertions(+), 10 deletions(-) -- 2.11.0 diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 9a7def7c3237..90659eb29660 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1071,6 +1071,52 @@ static int spi_transfer_wait(struct spi_controller *ctlr, return 0; } +static void _spi_transfer_delay_ns(u32 ns) +{ + if (!ns) + return; + if (ns <= 1000) { + ndelay(ns); + } else { + u32 us = DIV_ROUND_UP(ns, 1000); + + if (us <= 10) + udelay(us); + else + usleep_range(us, us + DIV_ROUND_UP(us, 10)); + } +} + +static void _spi_transfer_cs_change_delay(struct spi_message *msg, + struct spi_transfer *xfer) +{ + u32 delay = xfer->cs_change_delay; + u32 unit = xfer->cs_change_delay_unit; + + /* return early on "fast" mode - for everything but USECS */ + if (!delay && unit != SPI_DELAY_UNIT_USECS) + return; + + switch (unit) { + case SPI_DELAY_UNIT_USECS: + /* for compatibility use default of 10us */ + if (!delay) + delay = 10000; + else + delay *= 1000; + break; + case SPI_DELAY_UNIT_NSECS: /* nothing to do here */ + break; + default: + dev_err_once(&msg->spi->dev, + "Use of unsupported delay unit %i, using default of 10us\n", + xfer->cs_change_delay_unit); + delay = 10000; + } + /* now sleep for the requested amount of time */ + _spi_transfer_delay_ns(delay); +} + /* * spi_transfer_one_message - Default implementation of transfer_one_message() * @@ -1129,14 +1175,8 @@ static int spi_transfer_one_message(struct spi_controller *ctlr, if (msg->status != -EINPROGRESS) goto out; - if (xfer->delay_usecs) { - u16 us = xfer->delay_usecs; - - if (us <= 10) - udelay(us); - else - usleep_range(us, us + DIV_ROUND_UP(us, 10)); - } + if (xfer->delay_usecs) + _spi_transfer_delay_ns(xfer->delay_usecs * 1000); if (xfer->cs_change) { if (list_is_last(&xfer->transfer_list, @@ -1144,7 +1184,7 @@ static int spi_transfer_one_message(struct spi_controller *ctlr, keep_cs = true; } else { spi_set_cs(msg->spi, false); - udelay(10); + _spi_transfer_cs_change_delay(msg, xfer); spi_set_cs(msg->spi, true); } } @@ -3642,4 +3682,3 @@ static int __init spi_init(void) * include needing to have boardinfo data structures be much more public. */ postcore_initcall(spi_init); - diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 314d922ca607..f2ce1fb403ef 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -703,6 +703,9 @@ extern void spi_res_release(struct spi_controller *ctlr, * @bits_per_word: select a bits_per_word other than the device default * for this transfer. If 0 the default (from @spi_device) is used. * @cs_change: affects chipselect after this transfer completes + * @cs_change_delay: delay between cs deassert and assert when + * @cs_change is set and @spi_transfer is not the last in @spi_message + * @cs_change_delay_unit: unit of cs_change_delay * @delay_usecs: microseconds to delay after this transfer before * (optionally) changing the chipselect status, then starting * the next transfer or completing this @spi_message. @@ -789,6 +792,10 @@ struct spi_transfer { #define SPI_NBITS_QUAD 0x04 /* 4bits transfer */ u8 bits_per_word; u16 delay_usecs; + u16 cs_change_delay; + u8 cs_change_delay_unit; +#define SPI_DELAY_UNIT_USECS 0 +#define SPI_DELAY_UNIT_NSECS 1 u32 speed_hz; u16 word_delay;