linux/drivers/spi/spi-at91-usart.c

// SPDX-License-Identifier: GPL-2.0
//
// Driver for AT91 USART Controllers as SPI
//
// Copyright (C) 2018 Microchip Technology Inc.
//
// Author: Radu Pirea <radu.pirea@microchip.com>

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_gpio.h>
#include <linux/platform_device.h>

#include <linux/spi/spi.h>

#define US_CR			0x00
#define US_MR			0x04
#define US_IER			0x08
#define US_IDR			0x0C
#define US_CSR			0x14
#define US_RHR			0x18
#define US_THR			0x1C
#define US_BRGR			0x20
#define US_VERSION		0xFC

#define US_CR_RSTRX		BIT(2)
#define US_CR_RSTTX		BIT(3)
#define US_CR_RXEN		BIT(4)
#define US_CR_RXDIS		BIT(5)
#define US_CR_TXEN		BIT(6)
#define US_CR_TXDIS		BIT(7)

#define US_MR_SPI_MASTER	0x0E
#define US_MR_CHRL		GENMASK(7, 6)
#define US_MR_CPHA		BIT(8)
#define US_MR_CPOL		BIT(16)
#define US_MR_CLKO		BIT(18)
#define US_MR_WRDBT		BIT(20)
#define US_MR_LOOP		BIT(15)

#define US_IR_RXRDY		BIT(0)
#define US_IR_TXRDY		BIT(1)
#define US_IR_OVRE		BIT(5)

#define US_BRGR_SIZE		BIT(16)

#define US_MIN_CLK_DIV		0x06
#define US_MAX_CLK_DIV		BIT(16)

#define US_RESET		(US_CR_RSTRX | US_CR_RSTTX)
#define US_DISABLE		(US_CR_RXDIS | US_CR_TXDIS)
#define US_ENABLE		(US_CR_RXEN | US_CR_TXEN)
#define US_OVRE_RXRDY_IRQS	(US_IR_OVRE | US_IR_RXRDY)

#define US_INIT \
	(US_MR_SPI_MASTER | US_MR_CHRL | US_MR_CLKO | US_MR_WRDBT)

/* Register access macros */
#define at91_usart_spi_readl(port, reg) \
	readl_relaxed((port)->regs + US_##reg)
#define at91_usart_spi_writel(port, reg, value) \
	writel_relaxed((value), (port)->regs + US_##reg)

#define at91_usart_spi_readb(port, reg) \
	readb_relaxed((port)->regs + US_##reg)
#define at91_usart_spi_writeb(port, reg, value) \
	writeb_relaxed((value), (port)->regs + US_##reg)

struct at91_usart_spi {
	struct spi_transfer	*current_transfer;
	void __iomem		*regs;
	struct device		*dev;
	struct clk		*clk;

	/*used in interrupt to protect data reading*/
	spinlock_t		lock;

	int			irq;
	unsigned int		current_tx_remaining_bytes;
	unsigned int		current_rx_remaining_bytes;

	u32			spi_clk;
	u32			status;

	bool			xfer_failed;
};

static inline u32 at91_usart_spi_tx_ready(struct at91_usart_spi *aus)
{
	return aus->status & US_IR_TXRDY;
}

static inline u32 at91_usart_spi_rx_ready(struct at91_usart_spi *aus)
{
	return aus->status & US_IR_RXRDY;
}

static inline u32 at91_usart_spi_check_overrun(struct at91_usart_spi *aus)
{
	return aus->status & US_IR_OVRE;
}

static inline u32 at91_usart_spi_read_status(struct at91_usart_spi *aus)
{
	aus->status = at91_usart_spi_readl(aus, CSR);
	return aus->status;
}

static inline void at91_usart_spi_tx(struct at91_usart_spi *aus)
{
	unsigned int len = aus->current_transfer->len;
	unsigned int remaining = aus->current_tx_remaining_bytes;
	const u8  *tx_buf = aus->current_transfer->tx_buf;

	if (!remaining)
		return;

	if (at91_usart_spi_tx_ready(aus)) {
		at91_usart_spi_writeb(aus, THR, tx_buf[len - remaining]);
		aus->current_tx_remaining_bytes--;
	}
}

static inline void at91_usart_spi_rx(struct at91_usart_spi *aus)
{
	int len = aus->current_transfer->len;
	int remaining = aus->current_rx_remaining_bytes;
	u8  *rx_buf = aus->current_transfer->rx_buf;

	if (!remaining)
		return;

	rx_buf[len - remaining] = at91_usart_spi_readb(aus, RHR);
	aus->current_rx_remaining_bytes--;
}

static inline void
at91_usart_spi_set_xfer_speed(struct at91_usart_spi *aus,
			      struct spi_transfer *xfer)
{
	at91_usart_spi_writel(aus, BRGR,
			      DIV_ROUND_UP(aus->spi_clk, xfer->speed_hz));
}

static irqreturn_t at91_usart_spi_interrupt(int irq, void *dev_id)
{
	struct spi_controller *controller = dev_id;
	struct at91_usart_spi *aus = spi_master_get_devdata(controller);

	spin_lock(&aus->lock);
	at91_usart_spi_read_status(aus);

	if (at91_usart_spi_check_overrun(aus)) {
		aus->xfer_failed = true;
		at91_usart_spi_writel(aus, IDR, US_IR_OVRE | US_IR_RXRDY);
		spin_unlock(&aus->lock);
		return IRQ_HANDLED;
	}

	if (at91_usart_spi_rx_ready(aus)) {
		at91_usart_spi_rx(aus);
		spin_unlock(&aus->lock);
		return IRQ_HANDLED;
	}

	spin_unlock(&aus->lock);

	return IRQ_NONE;
}

static int at91_usart_spi_setup(struct spi_device *spi)
{
	struct at91_usart_spi *aus = spi_master_get_devdata(spi->controller);
	u32 *ausd = spi->controller_state;
	unsigned int mr = at91_usart_spi_readl(aus, MR);
	u8 bits = spi->bits_per_word;

	if (bits != 8) {
		dev_dbg(&spi->dev, "Only 8 bits per word are supported\n");
		return -EINVAL;
	}

	if (spi->mode & SPI_CPOL)
		mr |= US_MR_CPOL;
	else
		mr &= ~US_MR_CPOL;

	if (spi->mode & SPI_CPHA)
		mr |= US_MR_CPHA;
	else
		mr &= ~US_MR_CPHA;

	if (spi->mode & SPI_LOOP)
		mr |= US_MR_LOOP;
	else
		mr &= ~US_MR_LOOP;

	if (!ausd) {
		ausd = kzalloc(sizeof(*ausd), GFP_KERNEL);
		if (!ausd)
			return -ENOMEM;

		spi->controller_state = ausd;
	}

	*ausd = mr;

	dev_dbg(&spi->dev,
		"setup: bpw %u mode 0x%x -> mr %d %08x\n",
		bits, spi->mode, spi->chip_select, mr);

	return 0;
}

static int at91_usart_spi_transfer_one(struct spi_controller *ctlr,
				       struct spi_device *spi,
				       struct spi_transfer *xfer)
{
	struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);

	at91_usart_spi_set_xfer_speed(aus, xfer);
	aus->xfer_failed = false;
	aus->current_transfer = xfer;
	aus->current_tx_remaining_bytes = xfer->len;
	aus->current_rx_remaining_bytes = xfer->len;

	while ((aus->current_tx_remaining_bytes ||
		aus->current_rx_remaining_bytes) && !aus->xfer_failed) {
		at91_usart_spi_read_status(aus);
		at91_usart_spi_tx(aus);
		cpu_relax();
	}

	if (aus->xfer_failed) {
		dev_err(aus->dev, "Overrun!\n");
		return -EIO;
	}

	return 0;
}

static int at91_usart_spi_prepare_message(struct spi_controller *ctlr,
					  struct spi_message *message)
{
	struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
	struct spi_device *spi = message->spi;
	u32 *ausd = spi->controller_state;

	at91_usart_spi_writel(aus, CR, US_ENABLE);
	at91_usart_spi_writel(aus, IER, US_OVRE_RXRDY_IRQS);
	at91_usart_spi_writel(aus, MR, *ausd);

	return 0;
}

static int at91_usart_spi_unprepare_message(struct spi_controller *ctlr,
					    struct spi_message *message)
{
	struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);

	at91_usart_spi_writel(aus, CR, US_RESET | US_DISABLE);
	at91_usart_spi_writel(aus, IDR, US_OVRE_RXRDY_IRQS);

	return 0;
}

static void at91_usart_spi_cleanup(struct spi_device *spi)
{
	struct at91_usart_spi_device *ausd = spi->controller_state;

	spi->controller_state = NULL;
	kfree(ausd);
}

static void at91_usart_spi_init(struct at91_usart_spi *aus)
{
	at91_usart_spi_writel(aus, MR, US_INIT);
	at91_usart_spi_writel(aus, CR, US_RESET | US_DISABLE);
}

static int at91_usart_gpio_setup(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.parent->of_node;
	int i;
	int ret;
	int nb;

	if (!np)
		return -EINVAL;

	nb = of_gpio_named_count(np, "cs-gpios");
	for (i = 0; i < nb; i++) {
		int cs_gpio = of_get_named_gpio(np, "cs-gpios", i);

		if (cs_gpio < 0)
			return cs_gpio;

		if (gpio_is_valid(cs_gpio)) {
			ret = devm_gpio_request_one(&pdev->dev, cs_gpio,
						    GPIOF_DIR_OUT,
						    dev_name(&pdev->dev));
			if (ret)
				return ret;
		}
	}

	return 0;
}

static int at91_usart_spi_probe(struct platform_device *pdev)
{
	struct resource *regs;
	struct spi_controller *controller;
	struct at91_usart_spi *aus;
	struct clk *clk;
	int irq;
	int ret;

	regs = platform_get_resource(to_platform_device(pdev->dev.parent),
				     IORESOURCE_MEM, 0);
	if (!regs)
		return -EINVAL;

	irq = platform_get_irq(to_platform_device(pdev->dev.parent), 0);
	if (irq < 0)
		return irq;

	clk = devm_clk_get(pdev->dev.parent, "usart");
	if (IS_ERR(clk))
		return PTR_ERR(clk);

	ret = -ENOMEM;
	controller = spi_alloc_master(&pdev->dev, sizeof(*aus));
	if (!controller)
		goto at91_usart_spi_probe_fail;

	ret = at91_usart_gpio_setup(pdev);
	if (ret)
		goto at91_usart_spi_probe_fail;

	controller->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP | SPI_CS_HIGH;
	controller->dev.of_node = pdev->dev.parent->of_node;
	controller->bits_per_word_mask = SPI_BPW_MASK(8);
	controller->setup = at91_usart_spi_setup;
	controller->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
	controller->transfer_one = at91_usart_spi_transfer_one;
	controller->prepare_message = at91_usart_spi_prepare_message;
	controller->unprepare_message = at91_usart_spi_unprepare_message;
	controller->cleanup = at91_usart_spi_cleanup;
	controller->max_speed_hz = DIV_ROUND_UP(clk_get_rate(clk),
						US_MIN_CLK_DIV);
	controller->min_speed_hz = DIV_ROUND_UP(clk_get_rate(clk),
						US_MAX_CLK_DIV);
	platform_set_drvdata(pdev, controller);

	aus = spi_master_get_devdata(controller);

	aus->dev = &pdev->dev;
	aus->regs = devm_ioremap_resource(&pdev->dev, regs);
	if (IS_ERR(aus->regs)) {
		ret = PTR_ERR(aus->regs);
		goto at91_usart_spi_probe_fail;
	}

	aus->irq = irq;
	aus->clk = clk;

	ret = devm_request_irq(&pdev->dev, irq, at91_usart_spi_interrupt, 0,
			       dev_name(&pdev->dev), controller);
	if (ret)
		goto at91_usart_spi_probe_fail;

	ret = clk_prepare_enable(clk);
	if (ret)
		goto at91_usart_spi_probe_fail;

	aus->spi_clk = clk_get_rate(clk);
	at91_usart_spi_init(aus);

	spin_lock_init(&aus->lock);
	ret = devm_spi_register_master(&pdev->dev, controller);
	if (ret)
		goto at91_usart_fail_register_master;

	dev_info(&pdev->dev,
		 "AT91 USART SPI Controller version 0x%x at %pa (irq %d)\n",
		 at91_usart_spi_readl(aus, VERSION),
		 &regs->start, irq);

	return 0;

at91_usart_fail_register_master:
	clk_disable_unprepare(clk);
at91_usart_spi_probe_fail:
	spi_master_put(controller);
	return ret;
}

static int at91_usart_spi_remove(struct platform_device *pdev)
{
	struct spi_controller *ctlr = platform_get_drvdata(pdev);
	struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);

	clk_disable_unprepare(aus->clk);

	return 0;
}

static const struct of_device_id at91_usart_spi_dt_ids[] = {
	{ .compatible = "microchip,at91sam9g45-usart-spi"},
	{ /* sentinel */}
};

MODULE_DEVICE_TABLE(of, at91_usart_spi_dt_ids);

static struct platform_driver at91_usart_spi_driver = {
	.driver = {
		.name = "at91_usart_spi",
	},
	.probe = at91_usart_spi_probe,
	.remove = at91_usart_spi_remove,
};

module_platform_driver(at91_usart_spi_driver);

MODULE_DESCRIPTION("Microchip AT91 USART SPI Controller driver");
MODULE_AUTHOR("Radu Pirea <radu.pirea@microchip.com>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:at91_usart_spi");