From patchwork Tue Jan 14 23:38:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Packham X-Patchwork-Id: 11332971 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 870D113A0 for ; Tue, 14 Jan 2020 23:39:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5BCE524658 for ; Tue, 14 Jan 2020 23:39:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=alliedtelesis.co.nz header.i=@alliedtelesis.co.nz header.b="ShJCmUzM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728892AbgANXjS (ORCPT ); Tue, 14 Jan 2020 18:39:18 -0500 Received: from gate2.alliedtelesis.co.nz ([202.36.163.20]:51183 "EHLO gate2.alliedtelesis.co.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728899AbgANXjM (ORCPT ); Tue, 14 Jan 2020 18:39:12 -0500 Received: from mmarshal3.atlnz.lc (mmarshal3.atlnz.lc [10.32.18.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by gate2.alliedtelesis.co.nz (Postfix) with ESMTPS id 1F38A891A9; Wed, 15 Jan 2020 12:39:10 +1300 (NZDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alliedtelesis.co.nz; s=mail181024; t=1579045150; bh=2gBER1PvepW7C/LmCCkcdmnlievV9RChs4q6y2glIWI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ShJCmUzMKbd8oSdsPgEnQ5avBWUFdaVdlM0bBCSYD8lLYOh8r9maUFNpwZptdTGRA TQVKo30T1zJe1QyziXtB1cSFI2DU219HXUlWHe1xxw/O3bMH8A2t49eTpxgnVlMB9T PXNJpm3ssh1xT4JcbIyqNgFPDY14qvm+XQzUwvbeHiFkSSzslJq5fuyQQSGFXGcfX5 vA8NpuzlRcoXaiHLepzkDKiC4zDZ5Z06HvasTG1gWShd6Ekku5D+BewIa0K2QQJ3G3 v+q3cEVaB4LpNWdrryBqC0imJd1rfAYtcZmNyVCRMdyifBDYjSREUUpOh3+odfZyYH GhhuYtqUP+C7w== Received: from smtp (Not Verified[10.32.16.33]) by mmarshal3.atlnz.lc with Trustwave SEG (v7,5,8,10121) id ; Wed, 15 Jan 2020 12:39:09 +1300 Received: from chrisp-dl.ws.atlnz.lc (chrisp-dl.ws.atlnz.lc [10.33.22.20]) by smtp (Postfix) with ESMTP id 73FDB13EF62; Wed, 15 Jan 2020 12:39:08 +1300 (NZDT) Received: by chrisp-dl.ws.atlnz.lc (Postfix, from userid 1030) id C37E7280071; Wed, 15 Jan 2020 12:39:08 +1300 (NZDT) From: Chris Packham To: broonie@kernel.org, robh+dt@kernel.org, mark.rutland@arm.com Cc: anthony.derosa@syscall7.com, linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Packham Subject: [PATCH 2/2] spi: Add generic SPI multiplexer Date: Wed, 15 Jan 2020 12:38:56 +1300 Message-Id: <20200114233857.25933-3-chris.packham@alliedtelesis.co.nz> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200114233857.25933-1-chris.packham@alliedtelesis.co.nz> References: <20200114233857.25933-1-chris.packham@alliedtelesis.co.nz> MIME-Version: 1.0 x-atlnz-ls: pat Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org Add a SPI device driver that sits in-band and provides a SPI controller which supports chip selects via a mux-control. This enables extra SPI devices to be connected with limited native chip selects. Signed-off-by: Chris Packham --- drivers/spi/Kconfig | 12 +++ drivers/spi/Makefile | 1 + drivers/spi/spi-mux.c | 189 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 202 insertions(+) create mode 100644 drivers/spi/spi-mux.c diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index 870f7797b56b..90df945490d9 100644 --- a/drivers/spi/Kconfig +++ b/drivers/spi/Kconfig @@ -880,6 +880,18 @@ config SPI_ZYNQMP_GQSPI # # Add new SPI master controllers in alphabetical order above this line # +# + +comment "SPI Multiplexer support" + +config SPI_MUX + tristate "SPI multiplexer support" + select MULTIPLEXER + help + This adds support for SPI multiplexers. Each SPI mux will be + accessible as a SPI controller, the devices behind the mux will appear + to be chip selects on this controller. It is still necessary to + select one or more specific mux-controller drivers. # # There are lots of SPI device types, with sensors and memory diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile index bb49c9e6d0a0..5f7593c84210 100644 --- a/drivers/spi/Makefile +++ b/drivers/spi/Makefile @@ -11,6 +11,7 @@ obj-$(CONFIG_SPI_MASTER) += spi.o obj-$(CONFIG_SPI_MEM) += spi-mem.o obj-$(CONFIG_SPI_SPIDEV) += spidev.o obj-$(CONFIG_SPI_LOOPBACK_TEST) += spi-loopback-test.o +obj-$(CONFIG_SPI_MUX) += spi-mux.o # SPI master controller drivers (bus) obj-$(CONFIG_SPI_ALTERA) += spi-altera.o diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c new file mode 100644 index 000000000000..8481067be5ae --- /dev/null +++ b/drivers/spi/spi-mux.c @@ -0,0 +1,189 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * General Purpose SPI multiplexer + */ + +#include +#include +#include +#include +#include +#include + +#define SPI_MUX_NO_CS ((unsigned int)-1) + +/** + * DOC: Driver description + * + * This driver supports a MUX on an SPI bus. This can be useful when you need + * more chip selects than the hardware peripherals support, or than are + * available in a particular board setup. + * + * The driver will create an additional SPI controller. Devices added under the + * mux will be handled as 'chip selects' on this controller. + */ + +/** + * struct spi_mux_priv - the basic spi_mux structure + * @spi: pointer to the device struct attached to the parent + * spi controller + * @current_cs: The current chip select set in the mux + * @child_mesg_complete: The mux replaces the complete callback in the child's + * message to its own callback; this field is used by the + * driver to store the child's callback during a transfer + * @child_mesg_context: Used to store the child's context to the callback + * @child_mesg_dev: Used to store the spi_device pointer to the child + * @mux: mux_control structure used to provide chip selects for + * downstream spi devices + */ +struct spi_mux_priv { + struct spi_device *spi; + unsigned int current_cs; + + void (*child_mesg_complete)(void *context); + void *child_mesg_context; + struct spi_device *child_mesg_dev; + struct mux_control *mux; +}; + +/* should not get called when the parent controller is doing a transfer */ +static int spi_mux_select(struct spi_device *spi) +{ + struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller); + int ret = 0; + + if (priv->current_cs != spi->chip_select) { + dev_dbg(&priv->spi->dev, + "setting up the mux for cs %d\n", + spi->chip_select); + + /* copy the child device's settings except for the cs */ + priv->spi->max_speed_hz = spi->max_speed_hz; + priv->spi->mode = spi->mode; + priv->spi->bits_per_word = spi->bits_per_word; + + ret = mux_control_select(priv->mux, spi->chip_select); + if (ret) + return ret; + + priv->current_cs = spi->chip_select; + } + + return ret; +} + +static int spi_mux_setup(struct spi_device *spi) +{ + struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller); + + /* + * can be called multiple times, won't do a valid setup now but we will + * change the settings when we do a transfer (necessary because we + * can't predict from which device it will be anyway) + */ + return spi_setup(priv->spi); +} + +static void spi_mux_complete_cb(void *context) +{ + struct spi_mux_priv *priv = (struct spi_mux_priv *)context; + struct spi_controller *ctlr = spi_get_drvdata(priv->spi); + struct spi_message *m = ctlr->cur_msg; + + m->complete = priv->child_mesg_complete; + m->context = priv->child_mesg_context; + m->spi = priv->child_mesg_dev; + spi_finalize_current_message(ctlr); + mux_control_deselect(priv->mux); +} + +static int spi_mux_transfer_one_message(struct spi_controller *ctlr, + struct spi_message *m) +{ + struct spi_mux_priv *priv = spi_controller_get_devdata(ctlr); + struct spi_device *spi = m->spi; + int ret; + + ret = spi_mux_select(spi); + if (ret) + return ret; + + /* + * Replace the complete callback, context and spi_device with our own + * pointers. Save originals + */ + priv->child_mesg_complete = m->complete; + priv->child_mesg_context = m->context; + priv->child_mesg_dev = m->spi; + + m->complete = spi_mux_complete_cb; + m->context = priv; + m->spi = priv->spi; + + /* do the transfer */ + ret = spi_async(priv->spi, m); + return ret; +} + +static int spi_mux_probe(struct spi_device *spi) +{ + struct spi_controller *ctlr; + struct spi_mux_priv *priv; + int ret; + + ctlr = spi_alloc_master(&spi->dev, sizeof(*priv)); + if (!ctlr) + return -ENOMEM; + + spi_set_drvdata(spi, ctlr); + priv = spi_controller_get_devdata(ctlr); + priv->spi = spi; + + priv->mux = devm_mux_control_get(&spi->dev, NULL); + ret = PTR_ERR_OR_ZERO(priv->mux); + if (ret) { + if (ret != -EPROBE_DEFER) + dev_err(&spi->dev, "failed to get control-mux\n"); + goto err_put_ctlr; + } + + priv->current_cs = SPI_MUX_NO_CS; + + /* supported modes are the same as our parent's */ + ctlr->mode_bits = spi->controller->mode_bits; + ctlr->flags = spi->controller->flags; + ctlr->transfer_one_message = spi_mux_transfer_one_message; + ctlr->setup = spi_mux_setup; + ctlr->num_chipselect = mux_control_states(priv->mux); + ctlr->bus_num = -1; + ctlr->dev.of_node = spi->dev.of_node; + + ret = devm_spi_register_controller(&spi->dev, ctlr); + if (ret) + goto err_put_ctlr; + + return ret; + +err_put_ctlr: + spi_controller_put(ctlr); + + return ret; +} + +static const struct of_device_id spi_mux_of_match[] = { + { .compatible = "spi-mux" }, + { }, +}; + +static struct spi_driver spi_mux_driver = { + .probe = spi_mux_probe, + .driver = { + .name = "spi-mux", + .of_match_table = spi_mux_of_match, + }, +}; + +module_spi_driver(spi_mux_driver); + +MODULE_DESCRIPTION("SPI multiplexer"); +MODULE_LICENSE("GPL");