/*
   * OpenCores tiny SPI master driver
   *
   * http://opencores.org/project,tiny_spi
   *
   * Copyright (C) 2011 Thomas Chou <thomas@wytron.com.tw>
   *
   * Based on spi_s3c24xx.c, which is:
   * Copyright (c) 2006 Ben Dooks
   * Copyright (c) 2006 Simtec Electronics
   *	Ben Dooks <ben@simtec.co.uk>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #include <linux/interrupt.h>
  #include <linux/errno.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/spi/spi.h>
  #include <linux/spi/spi_bitbang.h>
  #include <linux/spi/spi_oc_tiny.h>
  #include <linux/io.h>
  #include <linux/gpio.h>
  #include <linux/of.h>
  
  #define DRV_NAME "spi_oc_tiny"
  
  #define TINY_SPI_RXDATA 0
  #define TINY_SPI_TXDATA 4
  #define TINY_SPI_STATUS 8
  #define TINY_SPI_CONTROL 12
  #define TINY_SPI_BAUD 16
  
  #define TINY_SPI_STATUS_TXE 0x1
  #define TINY_SPI_STATUS_TXR 0x2
  
  struct tiny_spi {
  	/* bitbang has to be first */
  	struct spi_bitbang bitbang;
  	struct completion done;
  
  	void __iomem *base;
  	int irq;
  	unsigned int freq;
  	unsigned int baudwidth;
  	unsigned int baud;
  	unsigned int speed_hz;
  	unsigned int mode;
  	unsigned int len;
  	unsigned int txc, rxc;
  	const u8 *txp;
  	u8 *rxp;
  	int gpio_cs_count;
  	int *gpio_cs;
  };
  
  static inline struct tiny_spi *tiny_spi_to_hw(struct spi_device *sdev)
  {
  	return spi_master_get_devdata(sdev->master);
  }
  
  static unsigned int tiny_spi_baud(struct spi_device *spi, unsigned int hz)
  {
  	struct tiny_spi *hw = tiny_spi_to_hw(spi);
  
  	return min(DIV_ROUND_UP(hw->freq, hz * 2), (1U << hw->baudwidth)) - 1;
  }
  
  static void tiny_spi_chipselect(struct spi_device *spi, int is_active)
  {
  	struct tiny_spi *hw = tiny_spi_to_hw(spi);
  
  	if (hw->gpio_cs_count > 0) {
  		gpio_set_value(hw->gpio_cs[spi->chip_select],
  			(spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
  	}
  }
  
  static int tiny_spi_setup_transfer(struct spi_device *spi,
  				   struct spi_transfer *t)
  {
  	struct tiny_spi *hw = tiny_spi_to_hw(spi);
  	unsigned int baud = hw->baud;
  
  	if (t) {
  		if (t->speed_hz && t->speed_hz != hw->speed_hz)
  			baud = tiny_spi_baud(spi, t->speed_hz);
  	}
  	writel(baud, hw->base + TINY_SPI_BAUD);
  	writel(hw->mode, hw->base + TINY_SPI_CONTROL);
  	return 0;
  }
  
  static int tiny_spi_setup(struct spi_device *spi)
  {
  	struct tiny_spi *hw = tiny_spi_to_hw(spi);
  
  	if (spi->max_speed_hz != hw->speed_hz) {
  		hw->speed_hz = spi->max_speed_hz;
  		hw->baud = tiny_spi_baud(spi, hw->speed_hz);
  	}
  	hw->mode = spi->mode & (SPI_CPOL | SPI_CPHA);
  	return 0;
  }
  
  static inline void tiny_spi_wait_txr(struct tiny_spi *hw)
  {
  	while (!(readb(hw->base + TINY_SPI_STATUS) &
  		 TINY_SPI_STATUS_TXR))
  		cpu_relax();
  }
  
  static inline void tiny_spi_wait_txe(struct tiny_spi *hw)
  {
  	while (!(readb(hw->base + TINY_SPI_STATUS) &
  		 TINY_SPI_STATUS_TXE))
  		cpu_relax();
  }
  
  static int tiny_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
  {
  	struct tiny_spi *hw = tiny_spi_to_hw(spi);
  	const u8 *txp = t->tx_buf;
  	u8 *rxp = t->rx_buf;
  	unsigned int i;
  
  	if (hw->irq >= 0) {
  		/* use interrupt driven data transfer */
  		hw->len = t->len;
  		hw->txp = t->tx_buf;
  		hw->rxp = t->rx_buf;
  		hw->txc = 0;
  		hw->rxc = 0;
  
  		/* send the first byte */
  		if (t->len > 1) {
  			writeb(hw->txp ? *hw->txp++ : 0,
  			       hw->base + TINY_SPI_TXDATA);
  			hw->txc++;
  			writeb(hw->txp ? *hw->txp++ : 0,
  			       hw->base + TINY_SPI_TXDATA);
  			hw->txc++;
  			writeb(TINY_SPI_STATUS_TXR, hw->base + TINY_SPI_STATUS);
  		} else {
  			writeb(hw->txp ? *hw->txp++ : 0,
  			       hw->base + TINY_SPI_TXDATA);
  			hw->txc++;
  			writeb(TINY_SPI_STATUS_TXE, hw->base + TINY_SPI_STATUS);
  		}
  
  		wait_for_completion(&hw->done);
  	} else {
  		/* we need to tighten the transfer loop */
  		writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
  		for (i = 1; i < t->len; i++) {
  			writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
  
  			if (rxp || (i != t->len - 1))
  				tiny_spi_wait_txr(hw);
  			if (rxp)
  				*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
  		}
  		tiny_spi_wait_txe(hw);
  		if (rxp)
  			*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
  	}
  
  	return t->len;
  }
  
  static irqreturn_t tiny_spi_irq(int irq, void *dev)
  {
  	struct tiny_spi *hw = dev;
  
  	writeb(0, hw->base + TINY_SPI_STATUS);
  	if (hw->rxc + 1 == hw->len) {
  		if (hw->rxp)
  			*hw->rxp++ = readb(hw->base + TINY_SPI_RXDATA);
  		hw->rxc++;
  		complete(&hw->done);
  	} else {
  		if (hw->rxp)
  			*hw->rxp++ = readb(hw->base + TINY_SPI_TXDATA);
  		hw->rxc++;
  		if (hw->txc < hw->len) {
  			writeb(hw->txp ? *hw->txp++ : 0,
  			       hw->base + TINY_SPI_TXDATA);
  			hw->txc++;
  			writeb(TINY_SPI_STATUS_TXR,
  			       hw->base + TINY_SPI_STATUS);
  		} else {
  			writeb(TINY_SPI_STATUS_TXE,
  			       hw->base + TINY_SPI_STATUS);
  		}
  	}
  	return IRQ_HANDLED;
  }
  
  #ifdef CONFIG_OF
  #include <linux/of_gpio.h>
  
  static int tiny_spi_of_probe(struct platform_device *pdev)
  {
  	struct tiny_spi *hw = platform_get_drvdata(pdev);
  	struct device_node *np = pdev->dev.of_node;
  	unsigned int i;
  	u32 val;
  
  	if (!np)
  		return 0;
  	hw->gpio_cs_count = of_gpio_count(np);
  	if (hw->gpio_cs_count > 0) {
  		hw->gpio_cs = devm_kzalloc(&pdev->dev,
  				hw->gpio_cs_count * sizeof(unsigned int),
  				GFP_KERNEL);
  		if (!hw->gpio_cs)
  			return -ENOMEM;
  	}
  	for (i = 0; i < hw->gpio_cs_count; i++) {
  		hw->gpio_cs[i] = of_get_gpio_flags(np, i, NULL);
  		if (hw->gpio_cs[i] < 0)
  			return -ENODEV;
  	}
  	hw->bitbang.master->dev.of_node = pdev->dev.of_node;
  	if (!of_property_read_u32(np, "clock-frequency", &val))
  		hw->freq = val;
  	if (!of_property_read_u32(np, "baud-width", &val))
  		hw->baudwidth = val;
  	return 0;
  }
  #else /* !CONFIG_OF */
  static int tiny_spi_of_probe(struct platform_device *pdev)
  {
  	return 0;
  }
  #endif /* CONFIG_OF */
  
  static int tiny_spi_probe(struct platform_device *pdev)
  {
  	struct tiny_spi_platform_data *platp = dev_get_platdata(&pdev->dev);
  	struct tiny_spi *hw;
  	struct spi_master *master;
  	struct resource *res;
  	unsigned int i;
  	int err = -ENODEV;
  
  	master = spi_alloc_master(&pdev->dev, sizeof(struct tiny_spi));
  	if (!master)
  		return err;
  
  	/* setup the master state. */
  	master->bus_num = pdev->id;
  	master->num_chipselect = 255;
  	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
  	master->setup = tiny_spi_setup;
  
  	hw = spi_master_get_devdata(master);
  	platform_set_drvdata(pdev, hw);
  
  	/* setup the state for the bitbang driver */
  	hw->bitbang.master = master;
  	hw->bitbang.setup_transfer = tiny_spi_setup_transfer;
  	hw->bitbang.chipselect = tiny_spi_chipselect;
  	hw->bitbang.txrx_bufs = tiny_spi_txrx_bufs;
  
  	/* find and map our resources */
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	hw->base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(hw->base)) {
  		err = PTR_ERR(hw->base);
  		goto exit;
  	}
  	/* irq is optional */
  	hw->irq = platform_get_irq(pdev, 0);
  	if (hw->irq >= 0) {
  		init_completion(&hw->done);
  		err = devm_request_irq(&pdev->dev, hw->irq, tiny_spi_irq, 0,
  				       pdev->name, hw);
  		if (err)
  			goto exit;
  	}
  	/* find platform data */
  	if (platp) {
  		hw->gpio_cs_count = platp->gpio_cs_count;
  		hw->gpio_cs = platp->gpio_cs;
  		if (platp->gpio_cs_count && !platp->gpio_cs) {
  			err = -EBUSY;
  			goto exit;
  		}
  		hw->freq = platp->freq;
  		hw->baudwidth = platp->baudwidth;
  	} else {
  		err = tiny_spi_of_probe(pdev);
  		if (err)
  			goto exit;
  	}
  	for (i = 0; i < hw->gpio_cs_count; i++) {
  		err = gpio_request(hw->gpio_cs[i], dev_name(&pdev->dev));
  		if (err)
  			goto exit_gpio;
  		gpio_direction_output(hw->gpio_cs[i], 1);
  	}
  	hw->bitbang.master->num_chipselect = max(1, hw->gpio_cs_count);
  
  	/* register our spi controller */
  	err = spi_bitbang_start(&hw->bitbang);
  	if (err)
  		goto exit;
  	dev_info(&pdev->dev, "base %p, irq %d
  ", hw->base, hw->irq);
  
  	return 0;
  
  exit_gpio:
  	while (i-- > 0)
  		gpio_free(hw->gpio_cs[i]);
  exit:
  	spi_master_put(master);
  	return err;
  }
  
  static int tiny_spi_remove(struct platform_device *pdev)
  {
  	struct tiny_spi *hw = platform_get_drvdata(pdev);
  	struct spi_master *master = hw->bitbang.master;
  	unsigned int i;
  
  	spi_bitbang_stop(&hw->bitbang);
  	for (i = 0; i < hw->gpio_cs_count; i++)
  		gpio_free(hw->gpio_cs[i]);
  	spi_master_put(master);
  	return 0;
  }
  
  #ifdef CONFIG_OF
  static const struct of_device_id tiny_spi_match[] = {
  	{ .compatible = "opencores,tiny-spi-rtlsvn2", },
  	{},
  };
  MODULE_DEVICE_TABLE(of, tiny_spi_match);
  #endif /* CONFIG_OF */
  
  static struct platform_driver tiny_spi_driver = {
  	.probe = tiny_spi_probe,
  	.remove = tiny_spi_remove,
  	.driver = {
  		.name = DRV_NAME,
  		.pm = NULL,
  		.of_match_table = of_match_ptr(tiny_spi_match),
  	},
  };
  module_platform_driver(tiny_spi_driver);
  
  MODULE_DESCRIPTION("OpenCores tiny SPI driver");
  MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:" DRV_NAME);