From patchwork Thu Oct 6 08:30:30 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sascha Hauer X-Patchwork-Id: 613656 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01C3EC43217 for ; Thu, 6 Oct 2022 08:30:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230484AbiJFIam (ORCPT ); Thu, 6 Oct 2022 04:30:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230421AbiJFIaj (ORCPT ); Thu, 6 Oct 2022 04:30:39 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7C75925A2 for ; Thu, 6 Oct 2022 01:30:36 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1ogMH5-00041I-3G; Thu, 06 Oct 2022 10:30:35 +0200 Received: from [2a0a:edc0:0:1101:1d::28] (helo=dude02.red.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.94.2) (envelope-from ) id 1ogMH5-004v8P-GG; Thu, 06 Oct 2022 10:30:34 +0200 Received: from sha by dude02.red.stw.pengutronix.de with local (Exim 4.94.2) (envelope-from ) id 1ogMH3-009VHn-A2; Thu, 06 Oct 2022 10:30:33 +0200 From: Sascha Hauer To: linux-gpio@vger.kernel.org Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Walleij , Bartosz Golaszewski , kernel@pengutronix.de, Serge Semin , Sascha Hauer Subject: [PATCH v4 1/2] gpio: Add gpio latch driver Date: Thu, 6 Oct 2022 10:30:30 +0200 Message-Id: <20221006083031.2259006-2-s.hauer@pengutronix.de> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20221006083031.2259006-1-s.hauer@pengutronix.de> References: <20221006083031.2259006-1-s.hauer@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: devicetree@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org This driver implements a GPIO multiplexer based on latches connected to other GPIOs. A set of data GPIOs is connected to the data input of multiple latches. The clock input of each latch is driven by another set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins are output only. Signed-off-by: Sascha Hauer --- Notes: Changes since v3: - Introduce delays between GPIO toggles as suggested by Serge Semin Changes since v2: - Fix inconsistent licensing - document locks - use regular bit operations - include linux/mod_devicetable.h rather than linux/of_device.h - Put spinlock and mutex into a union to make clear that only one of them is used - rename __gpio_latch_set to gpio_latch_set_unlocked Changes since v1: - Use gpiod_set_value_cansleep when the underlying GPIOs might sleep - Move MODULE_DEVICE_TABLE near to the end drivers/gpio/Kconfig | 6 ++ drivers/gpio/Makefile | 1 + drivers/gpio/gpio-latch.c | 220 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 227 insertions(+) create mode 100644 drivers/gpio/gpio-latch.c diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index 0642f579196f2..e4603810ec910 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig @@ -1690,6 +1690,12 @@ config GPIO_AGGREGATOR industrial control context, to be operated from userspace using the GPIO chardev interface. +config GPIO_LATCH + tristate "GPIO latch driver" + help + Say yes here to enable a driver for GPIO multiplexers based on latches + connected to other GPIOs. + config GPIO_MOCKUP tristate "GPIO Testing Driver" select IRQ_SIM diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile index a0985d30f51bb..310fa08decc69 100644 --- a/drivers/gpio/Makefile +++ b/drivers/gpio/Makefile @@ -75,6 +75,7 @@ obj-$(CONFIG_GPIO_IT87) += gpio-it87.o obj-$(CONFIG_GPIO_IXP4XX) += gpio-ixp4xx.o obj-$(CONFIG_GPIO_JANZ_TTL) += gpio-janz-ttl.o obj-$(CONFIG_GPIO_KEMPLD) += gpio-kempld.o +obj-$(CONFIG_GPIO_LATCH) += gpio-latch.o obj-$(CONFIG_GPIO_LOGICVC) += gpio-logicvc.o obj-$(CONFIG_GPIO_LOONGSON1) += gpio-loongson1.o obj-$(CONFIG_GPIO_LOONGSON) += gpio-loongson.o diff --git a/drivers/gpio/gpio-latch.c b/drivers/gpio/gpio-latch.c new file mode 100644 index 0000000000000..a4ab8f1240450 --- /dev/null +++ b/drivers/gpio/gpio-latch.c @@ -0,0 +1,220 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * GPIO latch driver + * + * Copyright (C) 2022 Sascha Hauer + * + * This driver implements a GPIO (or better GPO as there is no input) + * multiplexer based on latches like this: + * + * CLK0 ----------------------. ,--------. + * CLK1 -------------------. `--------|> #0 | + * | | | + * OUT0 ----------------+--|-----------|D0 Q0|-----|< + * OUT1 --------------+-|--|-----------|D1 Q1|-----|< + * OUT2 ------------+-|-|--|-----------|D2 Q2|-----|< + * OUT3 ----------+-|-|-|--|-----------|D3 Q3|-----|< + * OUT4 --------+-|-|-|-|--|-----------|D4 Q4|-----|< + * OUT5 ------+-|-|-|-|-|--|-----------|D5 Q5|-----|< + * OUT6 ----+-|-|-|-|-|-|--|-----------|D6 Q6|-----|< + * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7 Q7|-----|< + * | | | | | | | | | `--------' + * | | | | | | | | | + * | | | | | | | | | ,--------. + * | | | | | | | | `-----------|> #1 | + * | | | | | | | | | | + * | | | | | | | `--------------|D0 Q0|-----|< + * | | | | | | `----------------|D1 Q1|-----|< + * | | | | | `------------------|D2 Q2|-----|< + * | | | | `--------------------|D3 Q3|-----|< + * | | | `----------------------|D4 Q4|-----|< + * | | `------------------------|D5 Q5|-----|< + * | `--------------------------|D6 Q6|-----|< + * `----------------------------|D7 Q7|-----|< + * `--------' + * + * The above is just an example. The actual number of number of latches and + * the number of inputs per latch is derived from the number of GPIOs given + * in the corresponding device tree properties. + */ + +#include +#include +#include +#include +#include +#include +#include + +#include "gpiolib.h" + +struct gpio_latch_priv { + struct gpio_chip gc; + struct gpio_descs *clk_gpios; + struct gpio_descs *latched_gpios; + int n_latched_gpios; + unsigned int setup_duration_ns; + unsigned int clock_duration_ns; + unsigned long *shadow; + /* + * Depending on whether any of the underlying GPIOs may sleep we either + * use a mutex or a spinlock to protect our shadow map. + */ + union { + struct mutex mutex; /* protects @shadow */ + spinlock_t spinlock; /* protects @shadow */ + }; +}; + +static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset) +{ + return GPIO_LINE_DIRECTION_OUT; +} + +static void gpio_latch_set_unlocked(struct gpio_latch_priv *priv, + void (*set)(struct gpio_desc *desc, int value), + unsigned int offset, bool val) +{ + int latch = offset / priv->n_latched_gpios; + int i; + + assign_bit(offset, priv->shadow, val); + + for (i = 0; i < priv->n_latched_gpios; i++) + set(priv->latched_gpios->desc[i], + test_bit(latch * priv->n_latched_gpios + i, priv->shadow)); + + ndelay(priv->setup_duration_ns); + set(priv->clk_gpios->desc[latch], 1); + udelay(priv->clock_duration_ns); + set(priv->clk_gpios->desc[latch], 0); + udelay(priv->clock_duration_ns); +} + +static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val) +{ + struct gpio_latch_priv *priv = gpiochip_get_data(gc); + unsigned long flags; + + spin_lock_irqsave(&priv->spinlock, flags); + + gpio_latch_set_unlocked(priv, gpiod_set_value, offset, val); + + spin_unlock_irqrestore(&priv->spinlock, flags); +} + +static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val) +{ + struct gpio_latch_priv *priv = gpiochip_get_data(gc); + + mutex_lock(&priv->mutex); + + gpio_latch_set_unlocked(priv, gpiod_set_value_cansleep, offset, val); + + mutex_unlock(&priv->mutex); +} + +static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv, unsigned int n_latches) +{ + int i; + + for (i = 0; i < n_latches; i++) + if (gpiod_cansleep(priv->clk_gpios->desc[i])) + return true; + + for (i = 0; i < priv->n_latched_gpios; i++) + if (gpiod_cansleep(priv->latched_gpios->desc[i])) + return true; + + return false; +} + +static int gpio_latch_probe(struct platform_device *pdev) +{ + struct gpio_latch_priv *priv; + unsigned int n_latches; + struct device_node *np = pdev->dev.of_node; + /* + * Some value which is still acceptable to delay in atomic context. + * If we need to go higher we might have to switch to usleep_range(), + * but that cannot ne used in atomic context and the driver would have + * to be adjusted to support that. + */ + unsigned int duration_ns_max = 5000; + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->clk_gpios = devm_gpiod_get_array(&pdev->dev, "clk", GPIOD_OUT_LOW); + if (IS_ERR(priv->clk_gpios)) + return PTR_ERR(priv->clk_gpios); + + priv->latched_gpios = devm_gpiod_get_array(&pdev->dev, "latched", GPIOD_OUT_LOW); + if (IS_ERR(priv->latched_gpios)) + return PTR_ERR(priv->latched_gpios); + + n_latches = priv->clk_gpios->ndescs; + priv->n_latched_gpios = priv->latched_gpios->ndescs; + + priv->shadow = devm_bitmap_zalloc(&pdev->dev, n_latches * priv->n_latched_gpios, + GFP_KERNEL); + if (!priv->shadow) + return -ENOMEM; + + if (gpio_latch_can_sleep(priv, n_latches)) { + priv->gc.can_sleep = true; + priv->gc.set = gpio_latch_set_can_sleep; + mutex_init(&priv->mutex); + } else { + priv->gc.can_sleep = false; + priv->gc.set = gpio_latch_set; + spin_lock_init(&priv->spinlock); + } + + of_property_read_u32(np, "setup-duration-ns", &priv->setup_duration_ns); + if (priv->setup_duration_ns > duration_ns_max) { + dev_warn(&pdev->dev, "setup-duration-ns too high, limit to %d\n", + duration_ns_max); + priv->setup_duration_ns = duration_ns_max; + } + + of_property_read_u32(np, "clock-duration-ns", &priv->clock_duration_ns); + if (priv->clock_duration_ns > duration_ns_max) { + dev_warn(&pdev->dev, "clock-duration-ns too high, limit to %d\n", + duration_ns_max); + priv->clock_duration_ns = duration_ns_max; + } + + priv->gc.get_direction = gpio_latch_get_direction; + priv->gc.ngpio = n_latches * priv->n_latched_gpios; + priv->gc.owner = THIS_MODULE; + priv->gc.base = -1; + priv->gc.parent = &pdev->dev; + + platform_set_drvdata(pdev, priv); + + return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv); +} + +static const struct of_device_id gpio_latch_ids[] = { + { + .compatible = "gpio-latch", + }, { + /* sentinel */ + } +}; +MODULE_DEVICE_TABLE(of, gpio_latch_ids); + +static struct platform_driver gpio_latch_driver = { + .driver = { + .name = "gpio-latch", + .of_match_table = gpio_latch_ids, + }, + .probe = gpio_latch_probe, +}; +module_platform_driver(gpio_latch_driver); + +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Sascha Hauer "); +MODULE_DESCRIPTION("GPIO latch driver");