gpio: mscc-bitbang-spi: Add a simple gpio driver for bitbgang spi

The VCore III SoCs such as the Luton but also the Ocelot can remap an SPI
flash directly in memory. However, for writing in the flash the
communication has to be done by software.

Each of the signal used for the SPI are exposed in a single register. In
order to be able to use the soft-spi driver, the management of this pin
is done through this simple gpio driver.

Even if the main purpose of this driver is to be used by soft-spi, it can
still be used as a normal gpio driver but with limitation: for example
the first pin can't be used as output.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

drivers/gpio/Kconfig

@@ -99,6 +99,13 @@ config LPC32XX_GPIO
 	help
 	  Support for the LPC32XX GPIO driver.
 
+config MSCC_BITBANG_SPI_GPIO
+	bool "Microsemi bitbang spi GPIO driver"
+	depends on DM_GPIO && SOC_VCOREIII
+	help
+	  Support controlling the GPIO used for SPI bitbang by software. Can
+	  be used by the VCoreIII SoCs, but it was mainly useful for Luton.
+
 config MSM_GPIO
 	bool "Qualcomm GPIO driver"
 	depends on DM_GPIO

drivers/gpio/Makefile

@@ -59,3 +59,4 @@ obj-$(CONFIG_MSM_GPIO)		+= msm_gpio.o
 obj-$(CONFIG_$(SPL_)PCF8575_GPIO)	+= pcf8575_gpio.o
 obj-$(CONFIG_PM8916_GPIO)	+= pm8916_gpio.o
 obj-$(CONFIG_MT7621_GPIO)	+= mt7621_gpio.o
+obj-$(CONFIG_MSCC_BITBANG_SPI_GPIO)	+= gpio-mscc-bitbang-spi.o

drivers/gpio/gpio-mscc-bitbang-spi.c

@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * Microsemi SoCs pinctrl driver
+ *
+ * Author: <gregory.clement@bootlin.com>
+ * License: Dual MIT/GPL
+ * Copyright (c) 2018 Microsemi Corporation
+ */
+
+#include <common.h>
+#include <asm-generic/gpio.h>
+#include <asm/io.h>
+#include <dm.h>
+#include <errno.h>
+
+enum {
+	SDI,
+	CS0,
+	CS1,
+	CS2,
+	CS3,
+	SDO,
+	SCK
+};
+
+static const int pinmap[] = { 0, 5, 6, 7, 8, 10, 12 };
+
+#define SW_SPI_CSn_OE	 0x1E	/* bits 1 to 4 */
+#define SW_SPI_CS0_OE	 BIT(1)
+#define SW_SPI_SDO_OE	 BIT(9)
+#define SW_SPI_SCK_OE	 BIT(11)
+#define SW_PIN_CTRL_MODE BIT(13)
+
+struct mscc_bb_spi_gpio {
+	void __iomem *regs;
+	u32 cache_val;
+};
+
+static int mscc_bb_spi_gpio_set(struct udevice *dev, unsigned oft, int val)
+{
+	struct mscc_bb_spi_gpio *gpio = dev_get_priv(dev);
+
+	if (val)
+		gpio->cache_val |= BIT(pinmap[oft]);
+	else
+		gpio->cache_val &= ~BIT(pinmap[oft]);
+
+	writel(gpio->cache_val, gpio->regs);
+
+	return 0;
+}
+
+static int mscc_bb_spi_gpio_direction_output(struct udevice *dev, unsigned oft,
+					     int val)
+{
+	if (oft == 0) {
+		pr_err("SW_SPI_DSI can't be used as output\n");
+		return -ENOTSUPP;
+	}
+
+	mscc_bb_spi_gpio_set(dev, oft, val);
+
+	return 0;
+}
+
+static int mscc_bb_spi_gpio_direction_input(struct udevice *dev, unsigned oft)
+{
+	return 0;
+}
+
+static int mscc_bb_spi_gpio_get(struct udevice *dev, unsigned int oft)
+{
+	struct mscc_bb_spi_gpio *gpio = dev_get_priv(dev);
+	u32 val = readl(gpio->regs);
+
+	return !!(val & BIT(pinmap[oft]));
+}
+
+static const struct dm_gpio_ops mscc_bb_spi_gpio_ops = {
+	.direction_output	= mscc_bb_spi_gpio_direction_output,
+	.direction_input	= mscc_bb_spi_gpio_direction_input,
+	.set_value		= mscc_bb_spi_gpio_set,
+	.get_value		= mscc_bb_spi_gpio_get,
+};
+
+static int mscc_bb_spi_gpio_probe(struct udevice *dev)
+{
+	struct mscc_bb_spi_gpio *gpio = dev_get_priv(dev);
+	struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+
+	gpio->regs = dev_remap_addr(dev);
+	if (!gpio->regs)
+		return -EINVAL;
+
+	uc_priv->bank_name = dev->name;
+	uc_priv->gpio_count = ARRAY_SIZE(pinmap);
+	/*
+	 * Enable software mode to control the SPI pin, enables the
+	 * output mode for most of the pin and initialize the cache
+	 * value in the same time
+	 */
+
+	gpio->cache_val = SW_PIN_CTRL_MODE | SW_SPI_SCK_OE | SW_SPI_SDO_OE |
+	    SW_SPI_CS0_OE;
+	writel(gpio->cache_val, gpio->regs);
+
+	return 0;
+}
+
+static const struct udevice_id mscc_bb_spi_gpio_ids[] = {
+	{.compatible = "mscc,spi-bitbang-gpio"},
+	{}
+};
+
+U_BOOT_DRIVER(gpio_mscc_bb_spi) = {
+	.name	= "gpio-mscc-spi-bitbang",
+	.id	= UCLASS_GPIO,
+	.ops	= &mscc_bb_spi_gpio_ops,
+	.probe	= mscc_bb_spi_gpio_probe,
+	.of_match = of_match_ptr(mscc_bb_spi_gpio_ids),
+	.priv_auto_alloc_size = sizeof(struct mscc_bb_spi_gpio),
+};