text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * SPI driver for Nvidia's Tegra20 Serial Flash Controller.
   *
   * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
   *
   * Author: Laxman Dewangan <ldewangan@nvidia.com>
   */
  
  #include <linux/clk.h>
  #include <linux/completion.h>
  #include <linux/delay.h>
  #include <linux/err.h>
  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/kthread.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/pm_runtime.h>
  #include <linux/of.h>
  #include <linux/of_device.h>
  #include <linux/reset.h>
  #include <linux/spi/spi.h>
  
  #define SPI_COMMAND				0x000
  #define SPI_GO					BIT(30)
  #define SPI_M_S					BIT(28)
  #define SPI_ACTIVE_SCLK_MASK			(0x3 << 26)
  #define SPI_ACTIVE_SCLK_DRIVE_LOW		(0 << 26)
  #define SPI_ACTIVE_SCLK_DRIVE_HIGH		(1 << 26)
  #define SPI_ACTIVE_SCLK_PULL_LOW		(2 << 26)
  #define SPI_ACTIVE_SCLK_PULL_HIGH		(3 << 26)
  
  #define SPI_CK_SDA_FALLING			(1 << 21)
  #define SPI_CK_SDA_RISING			(0 << 21)
  #define SPI_CK_SDA_MASK				(1 << 21)
  #define SPI_ACTIVE_SDA				(0x3 << 18)
  #define SPI_ACTIVE_SDA_DRIVE_LOW		(0 << 18)
  #define SPI_ACTIVE_SDA_DRIVE_HIGH		(1 << 18)
  #define SPI_ACTIVE_SDA_PULL_LOW			(2 << 18)
  #define SPI_ACTIVE_SDA_PULL_HIGH		(3 << 18)
  
  #define SPI_CS_POL_INVERT			BIT(16)
  #define SPI_TX_EN				BIT(15)
  #define SPI_RX_EN				BIT(14)
  #define SPI_CS_VAL_HIGH				BIT(13)
  #define SPI_CS_VAL_LOW				0x0
  #define SPI_CS_SW				BIT(12)
  #define SPI_CS_HW				0x0
  #define SPI_CS_DELAY_MASK			(7 << 9)
  #define SPI_CS3_EN				BIT(8)
  #define SPI_CS2_EN				BIT(7)
  #define SPI_CS1_EN				BIT(6)
  #define SPI_CS0_EN				BIT(5)
  
  #define SPI_CS_MASK			(SPI_CS3_EN | SPI_CS2_EN |	\
  					SPI_CS1_EN | SPI_CS0_EN)
  #define SPI_BIT_LENGTH(x)		(((x) & 0x1f) << 0)
  
  #define SPI_MODES			(SPI_ACTIVE_SCLK_MASK | SPI_CK_SDA_MASK)
  
  #define SPI_STATUS			0x004
  #define SPI_BSY				BIT(31)
  #define SPI_RDY				BIT(30)
  #define SPI_TXF_FLUSH			BIT(29)
  #define SPI_RXF_FLUSH			BIT(28)
  #define SPI_RX_UNF			BIT(27)
  #define SPI_TX_OVF			BIT(26)
  #define SPI_RXF_EMPTY			BIT(25)
  #define SPI_RXF_FULL			BIT(24)
  #define SPI_TXF_EMPTY			BIT(23)
  #define SPI_TXF_FULL			BIT(22)
  #define SPI_BLK_CNT(count)		(((count) & 0xffff) + 1)
  
  #define SPI_FIFO_ERROR			(SPI_RX_UNF | SPI_TX_OVF)
  #define SPI_FIFO_EMPTY			(SPI_TX_EMPTY | SPI_RX_EMPTY)
  
  #define SPI_RX_CMP			0x8
  #define SPI_DMA_CTL			0x0C
  #define SPI_DMA_EN			BIT(31)
  #define SPI_IE_RXC			BIT(27)
  #define SPI_IE_TXC			BIT(26)
  #define SPI_PACKED			BIT(20)
  #define SPI_RX_TRIG_MASK		(0x3 << 18)
  #define SPI_RX_TRIG_1W			(0x0 << 18)
  #define SPI_RX_TRIG_4W			(0x1 << 18)
  #define SPI_TX_TRIG_MASK		(0x3 << 16)
  #define SPI_TX_TRIG_1W			(0x0 << 16)
  #define SPI_TX_TRIG_4W			(0x1 << 16)
  #define SPI_DMA_BLK_COUNT(count)	(((count) - 1) & 0xFFFF)
  
  #define SPI_TX_FIFO			0x10
  #define SPI_RX_FIFO			0x20
  
  #define DATA_DIR_TX			(1 << 0)
  #define DATA_DIR_RX			(1 << 1)
  
  #define MAX_CHIP_SELECT			4
  #define SPI_FIFO_DEPTH			4
  #define SPI_DMA_TIMEOUT               (msecs_to_jiffies(1000))
  
  struct tegra_sflash_data {
  	struct device				*dev;
  	struct spi_master			*master;
  	spinlock_t				lock;
  
  	struct clk				*clk;
  	struct reset_control			*rst;
  	void __iomem				*base;
  	unsigned				irq;
  	u32					cur_speed;
  
  	struct spi_device			*cur_spi;
  	unsigned				cur_pos;
  	unsigned				cur_len;
  	unsigned				bytes_per_word;
  	unsigned				cur_direction;
  	unsigned				curr_xfer_words;
  
  	unsigned				cur_rx_pos;
  	unsigned				cur_tx_pos;
  
  	u32					tx_status;
  	u32					rx_status;
  	u32					status_reg;
  
  	u32					def_command_reg;
  	u32					command_reg;
  	u32					dma_control_reg;
  
  	struct completion			xfer_completion;
  	struct spi_transfer			*curr_xfer;
  };
  
  static int tegra_sflash_runtime_suspend(struct device *dev);
  static int tegra_sflash_runtime_resume(struct device *dev);
  
  static inline u32 tegra_sflash_readl(struct tegra_sflash_data *tsd,
  		unsigned long reg)
  {
  	return readl(tsd->base + reg);
  }
  
  static inline void tegra_sflash_writel(struct tegra_sflash_data *tsd,
  		u32 val, unsigned long reg)
  {
  	writel(val, tsd->base + reg);
  }
  
  static void tegra_sflash_clear_status(struct tegra_sflash_data *tsd)
  {
  	/* Write 1 to clear status register */
  	tegra_sflash_writel(tsd, SPI_RDY | SPI_FIFO_ERROR, SPI_STATUS);
  }
  
  static unsigned tegra_sflash_calculate_curr_xfer_param(
  	struct spi_device *spi, struct tegra_sflash_data *tsd,
  	struct spi_transfer *t)
  {
  	unsigned remain_len = t->len - tsd->cur_pos;
  	unsigned max_word;
  
  	tsd->bytes_per_word = DIV_ROUND_UP(t->bits_per_word, 8);
  	max_word = remain_len / tsd->bytes_per_word;
  	if (max_word > SPI_FIFO_DEPTH)
  		max_word = SPI_FIFO_DEPTH;
  	tsd->curr_xfer_words = max_word;
  	return max_word;
  }
  
  static unsigned tegra_sflash_fill_tx_fifo_from_client_txbuf(
  	struct tegra_sflash_data *tsd, struct spi_transfer *t)
  {
  	unsigned nbytes;
  	u32 status;
  	unsigned max_n_32bit = tsd->curr_xfer_words;
  	u8 *tx_buf = (u8 *)t->tx_buf + tsd->cur_tx_pos;
  
  	if (max_n_32bit > SPI_FIFO_DEPTH)
  		max_n_32bit = SPI_FIFO_DEPTH;
  	nbytes = max_n_32bit * tsd->bytes_per_word;
  
  	status = tegra_sflash_readl(tsd, SPI_STATUS);
  	while (!(status & SPI_TXF_FULL)) {
  		int i;
  		u32 x = 0;
  
  		for (i = 0; nbytes && (i < tsd->bytes_per_word);
  							i++, nbytes--)
  			x |= (u32)(*tx_buf++) << (i * 8);
  		tegra_sflash_writel(tsd, x, SPI_TX_FIFO);
  		if (!nbytes)
  			break;
  
  		status = tegra_sflash_readl(tsd, SPI_STATUS);
  	}
  	tsd->cur_tx_pos += max_n_32bit * tsd->bytes_per_word;
  	return max_n_32bit;
  }
  
  static int tegra_sflash_read_rx_fifo_to_client_rxbuf(
  		struct tegra_sflash_data *tsd, struct spi_transfer *t)
  {
  	u32 status;
  	unsigned int read_words = 0;
  	u8 *rx_buf = (u8 *)t->rx_buf + tsd->cur_rx_pos;
  
  	status = tegra_sflash_readl(tsd, SPI_STATUS);
  	while (!(status & SPI_RXF_EMPTY)) {
  		int i;
  		u32 x = tegra_sflash_readl(tsd, SPI_RX_FIFO);
  
  		for (i = 0; (i < tsd->bytes_per_word); i++)
  			*rx_buf++ = (x >> (i*8)) & 0xFF;
  		read_words++;
  		status = tegra_sflash_readl(tsd, SPI_STATUS);
  	}
  	tsd->cur_rx_pos += read_words * tsd->bytes_per_word;
  	return 0;
  }
  
  static int tegra_sflash_start_cpu_based_transfer(
  		struct tegra_sflash_data *tsd, struct spi_transfer *t)
  {
  	u32 val = 0;
  	unsigned cur_words;
  
  	if (tsd->cur_direction & DATA_DIR_TX)
  		val |= SPI_IE_TXC;
  
  	if (tsd->cur_direction & DATA_DIR_RX)
  		val |= SPI_IE_RXC;
  
  	tegra_sflash_writel(tsd, val, SPI_DMA_CTL);
  	tsd->dma_control_reg = val;
  
  	if (tsd->cur_direction & DATA_DIR_TX)
  		cur_words = tegra_sflash_fill_tx_fifo_from_client_txbuf(tsd, t);
  	else
  		cur_words = tsd->curr_xfer_words;
  	val |= SPI_DMA_BLK_COUNT(cur_words);
  	tegra_sflash_writel(tsd, val, SPI_DMA_CTL);
  	tsd->dma_control_reg = val;
  	val |= SPI_DMA_EN;
  	tegra_sflash_writel(tsd, val, SPI_DMA_CTL);
  	return 0;
  }
  
  static int tegra_sflash_start_transfer_one(struct spi_device *spi,
  		struct spi_transfer *t, bool is_first_of_msg,
  		bool is_single_xfer)
  {
  	struct tegra_sflash_data *tsd = spi_master_get_devdata(spi->master);
  	u32 speed;
  	u32 command;
  
  	speed = t->speed_hz;
  	if (speed != tsd->cur_speed) {
  		clk_set_rate(tsd->clk, speed);
  		tsd->cur_speed = speed;
  	}
  
  	tsd->cur_spi = spi;
  	tsd->cur_pos = 0;
  	tsd->cur_rx_pos = 0;
  	tsd->cur_tx_pos = 0;
  	tsd->curr_xfer = t;
  	tegra_sflash_calculate_curr_xfer_param(spi, tsd, t);
  	if (is_first_of_msg) {
  		command = tsd->def_command_reg;
  		command |= SPI_BIT_LENGTH(t->bits_per_word - 1);
  		command |= SPI_CS_VAL_HIGH;
  
  		command &= ~SPI_MODES;
  		if (spi->mode & SPI_CPHA)
  			command |= SPI_CK_SDA_FALLING;
  
  		if (spi->mode & SPI_CPOL)
  			command |= SPI_ACTIVE_SCLK_DRIVE_HIGH;
  		else
  			command |= SPI_ACTIVE_SCLK_DRIVE_LOW;
  		command |= SPI_CS0_EN << spi->chip_select;
  	} else {
  		command = tsd->command_reg;
  		command &= ~SPI_BIT_LENGTH(~0);
  		command |= SPI_BIT_LENGTH(t->bits_per_word - 1);
  		command &= ~(SPI_RX_EN | SPI_TX_EN);
  	}
  
  	tsd->cur_direction = 0;
  	if (t->rx_buf) {
  		command |= SPI_RX_EN;
  		tsd->cur_direction |= DATA_DIR_RX;
  	}
  	if (t->tx_buf) {
  		command |= SPI_TX_EN;
  		tsd->cur_direction |= DATA_DIR_TX;
  	}
  	tegra_sflash_writel(tsd, command, SPI_COMMAND);
  	tsd->command_reg = command;
  
  	return tegra_sflash_start_cpu_based_transfer(tsd, t);
  }
  
  static int tegra_sflash_transfer_one_message(struct spi_master *master,
  			struct spi_message *msg)
  {
  	bool is_first_msg = true;
  	int single_xfer;
  	struct tegra_sflash_data *tsd = spi_master_get_devdata(master);
  	struct spi_transfer *xfer;
  	struct spi_device *spi = msg->spi;
  	int ret;
  
  	msg->status = 0;
  	msg->actual_length = 0;
  	single_xfer = list_is_singular(&msg->transfers);
  	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
  		reinit_completion(&tsd->xfer_completion);
  		ret = tegra_sflash_start_transfer_one(spi, xfer,
  					is_first_msg, single_xfer);
  		if (ret < 0) {
  			dev_err(tsd->dev,
  				"spi can not start transfer, err %d\n", ret);
  			goto exit;
  		}
  		is_first_msg = false;
  		ret = wait_for_completion_timeout(&tsd->xfer_completion,
  						SPI_DMA_TIMEOUT);
  		if (WARN_ON(ret == 0)) {
  			dev_err(tsd->dev,
  				"spi transfer timeout, err %d\n", ret);
  			ret = -EIO;
  			goto exit;
  		}
  
  		if (tsd->tx_status ||  tsd->rx_status) {
  			dev_err(tsd->dev, "Error in Transfer\n");
  			ret = -EIO;
  			goto exit;
  		}
  		msg->actual_length += xfer->len;
  		if (xfer->cs_change && xfer->delay_usecs) {
  			tegra_sflash_writel(tsd, tsd->def_command_reg,
  					SPI_COMMAND);
  			udelay(xfer->delay_usecs);
  		}
  	}
  	ret = 0;
  exit:
  	tegra_sflash_writel(tsd, tsd->def_command_reg, SPI_COMMAND);
  	msg->status = ret;
  	spi_finalize_current_message(master);
  	return ret;
  }
  
  static irqreturn_t handle_cpu_based_xfer(struct tegra_sflash_data *tsd)
  {
  	struct spi_transfer *t = tsd->curr_xfer;
  	unsigned long flags;
  
  	spin_lock_irqsave(&tsd->lock, flags);
  	if (tsd->tx_status || tsd->rx_status || (tsd->status_reg & SPI_BSY)) {
  		dev_err(tsd->dev,
  			"CpuXfer ERROR bit set 0x%x\n", tsd->status_reg);
  		dev_err(tsd->dev,
  			"CpuXfer 0x%08x:0x%08x\n", tsd->command_reg,
  				tsd->dma_control_reg);
  		reset_control_assert(tsd->rst);
  		udelay(2);
  		reset_control_deassert(tsd->rst);
  		complete(&tsd->xfer_completion);
  		goto exit;
  	}
  
  	if (tsd->cur_direction & DATA_DIR_RX)
  		tegra_sflash_read_rx_fifo_to_client_rxbuf(tsd, t);
  
  	if (tsd->cur_direction & DATA_DIR_TX)
  		tsd->cur_pos = tsd->cur_tx_pos;
  	else
  		tsd->cur_pos = tsd->cur_rx_pos;
  
  	if (tsd->cur_pos == t->len) {
  		complete(&tsd->xfer_completion);
  		goto exit;
  	}
  
  	tegra_sflash_calculate_curr_xfer_param(tsd->cur_spi, tsd, t);
  	tegra_sflash_start_cpu_based_transfer(tsd, t);
  exit:
  	spin_unlock_irqrestore(&tsd->lock, flags);
  	return IRQ_HANDLED;
  }
  
  static irqreturn_t tegra_sflash_isr(int irq, void *context_data)
  {
  	struct tegra_sflash_data *tsd = context_data;
  
  	tsd->status_reg = tegra_sflash_readl(tsd, SPI_STATUS);
  	if (tsd->cur_direction & DATA_DIR_TX)
  		tsd->tx_status = tsd->status_reg & SPI_TX_OVF;
  
  	if (tsd->cur_direction & DATA_DIR_RX)
  		tsd->rx_status = tsd->status_reg & SPI_RX_UNF;
  	tegra_sflash_clear_status(tsd);
  
  	return handle_cpu_based_xfer(tsd);
  }
  
  static const struct of_device_id tegra_sflash_of_match[] = {
  	{ .compatible = "nvidia,tegra20-sflash", },
  	{}
  };
  MODULE_DEVICE_TABLE(of, tegra_sflash_of_match);
  
  static int tegra_sflash_probe(struct platform_device *pdev)
  {
  	struct spi_master	*master;
  	struct tegra_sflash_data	*tsd;
  	struct resource		*r;
  	int ret;
  	const struct of_device_id *match;
  
  	match = of_match_device(tegra_sflash_of_match, &pdev->dev);
  	if (!match) {
  		dev_err(&pdev->dev, "Error: No device match found\n");
  		return -ENODEV;
  	}
  
  	master = spi_alloc_master(&pdev->dev, sizeof(*tsd));
  	if (!master) {
  		dev_err(&pdev->dev, "master allocation failed\n");
  		return -ENOMEM;
  	}
  
  	/* the spi->mode bits understood by this driver: */
  	master->mode_bits = SPI_CPOL | SPI_CPHA;
  	master->transfer_one_message = tegra_sflash_transfer_one_message;
  	master->auto_runtime_pm = true;
  	master->num_chipselect = MAX_CHIP_SELECT;
  
  	platform_set_drvdata(pdev, master);
  	tsd = spi_master_get_devdata(master);
  	tsd->master = master;
  	tsd->dev = &pdev->dev;
  	spin_lock_init(&tsd->lock);
  
  	if (of_property_read_u32(tsd->dev->of_node, "spi-max-frequency",
  				 &master->max_speed_hz))
  		master->max_speed_hz = 25000000; /* 25MHz */
  
  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	tsd->base = devm_ioremap_resource(&pdev->dev, r);
  	if (IS_ERR(tsd->base)) {
  		ret = PTR_ERR(tsd->base);
  		goto exit_free_master;
  	}
  
  	tsd->irq = platform_get_irq(pdev, 0);
  	ret = request_irq(tsd->irq, tegra_sflash_isr, 0,
  			dev_name(&pdev->dev), tsd);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "Failed to register ISR for IRQ %d\n",
  					tsd->irq);
  		goto exit_free_master;
  	}
  
  	tsd->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(tsd->clk)) {
  		dev_err(&pdev->dev, "can not get clock\n");
  		ret = PTR_ERR(tsd->clk);
  		goto exit_free_irq;
  	}
  
  	tsd->rst = devm_reset_control_get_exclusive(&pdev->dev, "spi");
  	if (IS_ERR(tsd->rst)) {
  		dev_err(&pdev->dev, "can not get reset\n");
  		ret = PTR_ERR(tsd->rst);
  		goto exit_free_irq;
  	}
  
  	init_completion(&tsd->xfer_completion);
  	pm_runtime_enable(&pdev->dev);
  	if (!pm_runtime_enabled(&pdev->dev)) {
  		ret = tegra_sflash_runtime_resume(&pdev->dev);
  		if (ret)
  			goto exit_pm_disable;
  	}
  
  	ret = pm_runtime_get_sync(&pdev->dev);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "pm runtime get failed, e = %d\n", ret);
  		goto exit_pm_disable;
  	}
  
  	/* Reset controller */
  	reset_control_assert(tsd->rst);
  	udelay(2);
  	reset_control_deassert(tsd->rst);
  
  	tsd->def_command_reg  = SPI_M_S | SPI_CS_SW;
  	tegra_sflash_writel(tsd, tsd->def_command_reg, SPI_COMMAND);
  	pm_runtime_put(&pdev->dev);
  
  	master->dev.of_node = pdev->dev.of_node;
  	ret = devm_spi_register_master(&pdev->dev, master);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "can not register to master err %d\n", ret);
  		goto exit_pm_disable;
  	}
  	return ret;
  
  exit_pm_disable:
  	pm_runtime_disable(&pdev->dev);
  	if (!pm_runtime_status_suspended(&pdev->dev))
  		tegra_sflash_runtime_suspend(&pdev->dev);
  exit_free_irq:
  	free_irq(tsd->irq, tsd);
  exit_free_master:
  	spi_master_put(master);
  	return ret;
  }
  
  static int tegra_sflash_remove(struct platform_device *pdev)
  {
  	struct spi_master *master = platform_get_drvdata(pdev);
  	struct tegra_sflash_data	*tsd = spi_master_get_devdata(master);
  
  	free_irq(tsd->irq, tsd);
  
  	pm_runtime_disable(&pdev->dev);
  	if (!pm_runtime_status_suspended(&pdev->dev))
  		tegra_sflash_runtime_suspend(&pdev->dev);
  
  	return 0;
  }
  
  #ifdef CONFIG_PM_SLEEP
  static int tegra_sflash_suspend(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  
  	return spi_master_suspend(master);
  }
  
  static int tegra_sflash_resume(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  	struct tegra_sflash_data *tsd = spi_master_get_devdata(master);
  	int ret;
  
  	ret = pm_runtime_get_sync(dev);
  	if (ret < 0) {
  		dev_err(dev, "pm runtime failed, e = %d\n", ret);
  		return ret;
  	}
  	tegra_sflash_writel(tsd, tsd->command_reg, SPI_COMMAND);
  	pm_runtime_put(dev);
  
  	return spi_master_resume(master);
  }
  #endif
  
  static int tegra_sflash_runtime_suspend(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  	struct tegra_sflash_data *tsd = spi_master_get_devdata(master);
  
  	/* Flush all write which are in PPSB queue by reading back */
  	tegra_sflash_readl(tsd, SPI_COMMAND);
  
  	clk_disable_unprepare(tsd->clk);
  	return 0;
  }
  
  static int tegra_sflash_runtime_resume(struct device *dev)
  {
  	struct spi_master *master = dev_get_drvdata(dev);
  	struct tegra_sflash_data *tsd = spi_master_get_devdata(master);
  	int ret;
  
  	ret = clk_prepare_enable(tsd->clk);
  	if (ret < 0) {
  		dev_err(tsd->dev, "clk_prepare failed: %d\n", ret);
  		return ret;
  	}
  	return 0;
  }
  
  static const struct dev_pm_ops slink_pm_ops = {
  	SET_RUNTIME_PM_OPS(tegra_sflash_runtime_suspend,
  		tegra_sflash_runtime_resume, NULL)
  	SET_SYSTEM_SLEEP_PM_OPS(tegra_sflash_suspend, tegra_sflash_resume)
  };
  static struct platform_driver tegra_sflash_driver = {
  	.driver = {
  		.name		= "spi-tegra-sflash",
  		.pm		= &slink_pm_ops,
  		.of_match_table	= tegra_sflash_of_match,
  	},
  	.probe =	tegra_sflash_probe,
  	.remove =	tegra_sflash_remove,
  };
  module_platform_driver(tegra_sflash_driver);
  
  MODULE_ALIAS("platform:spi-tegra-sflash");
  MODULE_DESCRIPTION("NVIDIA Tegra20 Serial Flash Controller Driver");
  MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
  MODULE_LICENSE("GPL v2");
  