spi: add OpenCores tiny SPI driver

This patch adds support of OpenCores tiny SPI driver.

http://opencores.org/project,tiny_spi

Signed-off-by: Thomas Chou <[e-mail]>
Signed-off-by: Grant Likely <[e-mail]>

Documentation/devicetree/bindings/spi/spi_oc_tiny.txt

···
+OpenCores tiny SPI
+
+Required properties:
+- compatible : should be "opencores,tiny-spi-rtlsvn2".
+- gpios : should specify GPIOs used for chipselect.
+Optional properties:
+- clock-frequency : input clock frequency to the core.
+- baud-width: width, in bits, of the programmable divider used to scale
+	the input clock to SCLK.
+
+The clock-frequency and baud-width properties are needed only if the divider
+is programmable. They are not needed if the divider is fixed.

drivers/spi/Kconfig

···
 	  From MPC8536, 85xx platform uses the controller, and all P10xx,
 	  P20xx, P30xx,P40xx, P50xx uses this controller.
 
+config SPI_OC_TINY
+	tristate "OpenCores tiny SPI"
+	depends on GENERIC_GPIO
+	select SPI_BITBANG
+	help
+	  This is the driver for OpenCores tiny SPI master controller.
+
 config SPI_OMAP_UWIRE
 	tristate "OMAP1 MicroWire"
 	depends on ARCH_OMAP1

drivers/spi/Makefile

···
 obj-$(CONFIG_SPI_LM70_LLP)		+= spi_lm70llp.o
 obj-$(CONFIG_SPI_PXA2XX)		+= pxa2xx_spi.o
 obj-$(CONFIG_SPI_PXA2XX_PCI)		+= pxa2xx_spi_pci.o
+obj-$(CONFIG_SPI_OC_TINY)		+= spi_oc_tiny.o
 obj-$(CONFIG_SPI_OMAP_UWIRE)		+= omap_uwire.o
 obj-$(CONFIG_SPI_OMAP24XX)		+= omap2_mcspi.o
 obj-$(CONFIG_SPI_OMAP_100K)		+= omap_spi_100k.o

drivers/spi/spi_oc_tiny.c

···
+/*
+ * OpenCores tiny SPI master driver
+ *
+ * http://opencores.org/project,tiny_spi
+ *
+ * Copyright (C) 2011 Thomas Chou <[e-mail]>
+ *
+ * Based on spi_s3c24xx.c, which is:
+ * Copyright (c) 2006 Ben Dooks
+ * Copyright (c) 2006 Simtec Electronics
+ *	Ben Dooks <[e-mail]>
+ *
+ * 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/init.h>
+#include <linux/interrupt.h>
+#include <linux/errno.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;
+	unsigned 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) {
+		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 intrrupt 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 if (txp && rxp) {
+		/* we need to tighten the transfer loop */
+		writeb(*txp++, hw->base + TINY_SPI_TXDATA);
+		if (t->len > 1) {
+			writeb(*txp++, hw->base + TINY_SPI_TXDATA);
+			for (i = 2; i < t->len; i++) {
+				u8 rx, tx = *txp++;
+				tiny_spi_wait_txr(hw);
+				rx = readb(hw->base + TINY_SPI_TXDATA);
+				writeb(tx, hw->base + TINY_SPI_TXDATA);
+				*rxp++ = rx;
+			}
+			tiny_spi_wait_txr(hw);
+			*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
+		}
+		tiny_spi_wait_txe(hw);
+		*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
+	} else if (rxp) {
+		writeb(0, hw->base + TINY_SPI_TXDATA);
+		if (t->len > 1) {
+			writeb(0,
+			       hw->base + TINY_SPI_TXDATA);
+			for (i = 2; i < t->len; i++) {
+				u8 rx;
+				tiny_spi_wait_txr(hw);
+				rx = readb(hw->base + TINY_SPI_TXDATA);
+				writeb(0, hw->base + TINY_SPI_TXDATA);
+				*rxp++ = rx;
+			}
+			tiny_spi_wait_txr(hw);
+			*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
+		}
+		tiny_spi_wait_txe(hw);
+		*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
+	} else if (txp) {
+		writeb(*txp++, hw->base + TINY_SPI_TXDATA);
+		if (t->len > 1) {
+			writeb(*txp++, hw->base + TINY_SPI_TXDATA);
+			for (i = 2; i < t->len; i++) {
+				u8 tx = *txp++;
+				tiny_spi_wait_txr(hw);
+				writeb(tx, hw->base + TINY_SPI_TXDATA);
+			}
+		}
+		tiny_spi_wait_txe(hw);
+	} else {
+		writeb(0, hw->base + TINY_SPI_TXDATA);
+		if (t->len > 1) {
+			writeb(0, hw->base + TINY_SPI_TXDATA);
+			for (i = 2; i < t->len; i++) {
+				tiny_spi_wait_txr(hw);
+				writeb(0, hw->base + TINY_SPI_TXDATA);
+			}
+		}
+		tiny_spi_wait_txe(hw);
+	}
+	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 __devinit 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;
+	const __be32 *val;
+	int len;
+
+	if (!np)
+		return 0;
+	hw->gpio_cs_count = of_gpio_count(np);
+	if (hw->gpio_cs_count) {
+		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;
+	val = of_get_property(pdev->dev.of_node,
+			      "clock-frequency", &len);
+	if (val && len >= sizeof(__be32))
+		hw->freq = be32_to_cpup(val);
+	val = of_get_property(pdev->dev.of_node, "baud-width", &len);
+	if (val && len >= sizeof(__be32))
+		hw->baudwidth = be32_to_cpup(val);
+	return 0;
+}
+#else /* !CONFIG_OF */
+static int __devinit tiny_spi_of_probe(struct platform_device *pdev)
+{
+	return 0;
+}
+#endif /* CONFIG_OF */
+
+static int __devinit tiny_spi_probe(struct platform_device *pdev)
+{
+	struct tiny_spi_platform_data *platp = pdev->dev.platform_data;
+	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 = spi_master_get(master);
+	if (!hw->bitbang.master)
+		return err;
+	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);
+	if (!res)
+		goto exit_busy;
+	if (!devm_request_mem_region(&pdev->dev, res->start, resource_size(res),
+				     pdev->name))
+		goto exit_busy;
+	hw->base = devm_ioremap_nocache(&pdev->dev, res->start,
+					resource_size(res));
+	if (!hw->base)
+		goto exit_busy;
+	/* 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)
+			goto exit_busy;
+		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(1U, 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\n", hw->base, hw->irq);
+
+	return 0;
+
+exit_gpio:
+	while (i-- > 0)
+		gpio_free(hw->gpio_cs[i]);
+exit_busy:
+	err = -EBUSY;
+exit:
+	platform_set_drvdata(pdev, NULL);
+	spi_master_put(master);
+	return err;
+}
+
+static int __devexit 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]);
+	platform_set_drvdata(pdev, NULL);
+	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);
+#else /* CONFIG_OF */
+#define tiny_spi_match NULL
+#endif /* CONFIG_OF */
+
+static struct platform_driver tiny_spi_driver = {
+	.probe = tiny_spi_probe,
+	.remove = __devexit_p(tiny_spi_remove),
+	.driver = {
+		.name = DRV_NAME,
+		.owner = THIS_MODULE,
+		.pm = NULL,
+		.of_match_table = tiny_spi_match,
+	},
+};
+
+static int __init tiny_spi_init(void)
+{
+	return platform_driver_register(&tiny_spi_driver);
+}
+module_init(tiny_spi_init);
+
+static void __exit tiny_spi_exit(void)
+{
+	platform_driver_unregister(&tiny_spi_driver);
+}
+module_exit(tiny_spi_exit);
+
+MODULE_DESCRIPTION("OpenCores tiny SPI driver");
+MODULE_AUTHOR("Thomas Chou <[e-mail]>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" DRV_NAME);

include/linux/spi/spi_oc_tiny.h

···
+#ifndef _LINUX_SPI_SPI_OC_TINY_H
+#define _LINUX_SPI_SPI_OC_TINY_H
+
+/**
+ * struct tiny_spi_platform_data - platform data of the OpenCores tiny SPI
+ * @freq:	input clock freq to the core.
+ * @baudwidth:	baud rate divider width of the core.
+ * @gpio_cs_count:	number of gpio pins used for chipselect.
+ * @gpio_cs:	array of gpio pins used for chipselect.
+ *
+ * freq and baudwidth are used only if the divider is programmable.
+ */
+struct tiny_spi_platform_data {
+	unsigned int freq;
+	unsigned int baudwidth;
+	unsigned int gpio_cs_count;
+	int *gpio_cs;
+};
+
+#endif /* _LINUX_SPI_SPI_OC_TINY_H */