spi: sunxi: Add Allwinner A10 SPI controller driver

The older Allwinner SoCs (A10, A13, A10s and A20) all have the same SPI
controller.

Unfortunately, this SPI controller, even though quite similar, is significantly
different from the recently supported A31 SPI controller (different registers
offset, split/merged registers, etc.). Supporting both controllers in a single
driver would be unreasonable, hence the addition of a new driver.

Like its more recent counterpart, it supports DMA, but the driver only does PIO
until we have a dmaengine driver for this platform.
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/spi/spi-sun4i.txt

+Allwinner A10 SPI controller
+
+Required properties:
+- compatible: Should be "allwinner,sun4-a10-spi".
+- reg: Should contain register location and length.
+- interrupts: Should contain interrupt.
+- clocks: phandle to the clocks feeding the SPI controller. Two are
+          needed:
+  - "ahb": the gated AHB parent clock
+  - "mod": the parent module clock
+- clock-names: Must contain the clock names described just above
+
+Example:
+
+spi1: spi@01c06000 {
+	compatible = "allwinner,sun4i-a10-spi";
+	reg = <0x01c06000 0x1000>;
+	interrupts = <11>;
+	clocks = <&ahb_gates 21>, <&spi1_clk>;
+	clock-names = "ahb", "mod";
+	status = "disabled";
+	#address-cells = <1>;
+	#size-cells = <0>;
+};

drivers/spi/Kconfig

@@ -446,6 +446,12 @@ config SPI_SIRF
 	help
 	  SPI driver for CSR SiRFprimaII SoCs
 
+config SPI_SUN4I
+	tristate "Allwinner A10 SoCs SPI controller"
+	depends on ARCH_SUNXI || COMPILE_TEST
+	help
+	  SPI driver for Allwinner sun4i, sun5i and sun7i SoCs
+
 config SPI_SUN6I
 	tristate "Allwinner A31 SPI controller"
 	depends on ARCH_SUNXI || COMPILE_TEST

drivers/spi/Makefile

@@ -70,6 +70,7 @@ obj-$(CONFIG_SPI_SH_HSPI)		+= spi-sh-hspi.o
 obj-$(CONFIG_SPI_SH_MSIOF)		+= spi-sh-msiof.o
 obj-$(CONFIG_SPI_SH_SCI)		+= spi-sh-sci.o
 obj-$(CONFIG_SPI_SIRF)		+= spi-sirf.o
+obj-$(CONFIG_SPI_SUN4I)			+= spi-sun4i.o
 obj-$(CONFIG_SPI_SUN6I)			+= spi-sun6i.o
 obj-$(CONFIG_SPI_TEGRA114)		+= spi-tegra114.o
 obj-$(CONFIG_SPI_TEGRA20_SFLASH)	+= spi-tegra20-sflash.o

drivers/spi/spi-sun4i.c

+/*
+ * Copyright (C) 2012 - 2014 Allwinner Tech
+ * Pan Nan <pannan@allwinnertech.com>
+ *
+ * Copyright (C) 2014 Maxime Ripard
+ * Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/workqueue.h>
+
+#include <linux/spi/spi.h>
+
+#define SUN4I_FIFO_DEPTH		64
+
+#define SUN4I_RXDATA_REG		0x00
+
+#define SUN4I_TXDATA_REG		0x04
+
+#define SUN4I_CTL_REG			0x08
+#define SUN4I_CTL_ENABLE			BIT(0)
+#define SUN4I_CTL_MASTER			BIT(1)
+#define SUN4I_CTL_CPHA				BIT(2)
+#define SUN4I_CTL_CPOL				BIT(3)
+#define SUN4I_CTL_CS_ACTIVE_LOW			BIT(4)
+#define SUN4I_CTL_LMTF				BIT(6)
+#define SUN4I_CTL_TF_RST			BIT(8)
+#define SUN4I_CTL_RF_RST			BIT(9)
+#define SUN4I_CTL_XCH				BIT(10)
+#define SUN4I_CTL_CS_MASK			0x3000
+#define SUN4I_CTL_CS(cs)			(((cs) << 12) & SUN4I_CTL_CS_MASK)
+#define SUN4I_CTL_DHB				BIT(15)
+#define SUN4I_CTL_CS_MANUAL			BIT(16)
+#define SUN4I_CTL_CS_LEVEL			BIT(17)
+#define SUN4I_CTL_TP				BIT(18)
+
+#define SUN4I_INT_CTL_REG		0x0c
+#define SUN4I_INT_CTL_TC			BIT(16)
+
+#define SUN4I_INT_STA_REG		0x10
+
+#define SUN4I_DMA_CTL_REG		0x14
+
+#define SUN4I_WAIT_REG			0x18
+
+#define SUN4I_CLK_CTL_REG		0x1c
+#define SUN4I_CLK_CTL_CDR2_MASK			0xff
+#define SUN4I_CLK_CTL_CDR2(div)			((div) & SUN4I_CLK_CTL_CDR2_MASK)
+#define SUN4I_CLK_CTL_CDR1_MASK			0xf
+#define SUN4I_CLK_CTL_CDR1(div)			(((div) & SUN4I_CLK_CTL_CDR1_MASK) << 8)
+#define SUN4I_CLK_CTL_DRS			BIT(12)
+
+#define SUN4I_BURST_CNT_REG		0x20
+#define SUN4I_BURST_CNT(cnt)			((cnt) & 0xffffff)
+
+#define SUN4I_XMIT_CNT_REG		0x24
+#define SUN4I_XMIT_CNT(cnt)			((cnt) & 0xffffff)
+
+#define SUN4I_FIFO_STA_REG		0x28
+#define SUN4I_FIFO_STA_RF_CNT_MASK		0x7f
+#define SUN4I_FIFO_STA_RF_CNT_BITS		0
+#define SUN4I_FIFO_STA_TF_CNT_MASK		0x7f
+#define SUN4I_FIFO_STA_TF_CNT_BITS		16
+
+struct sun4i_spi {
+	struct spi_master	*master;
+	void __iomem		*base_addr;
+	struct clk		*hclk;
+	struct clk		*mclk;
+
+	struct completion	done;
+
+	const u8		*tx_buf;
+	u8			*rx_buf;
+	int			len;
+};
+
+static inline u32 sun4i_spi_read(struct sun4i_spi *sspi, u32 reg)
+{
+	return readl(sspi->base_addr + reg);
+}
+
+static inline void sun4i_spi_write(struct sun4i_spi *sspi, u32 reg, u32 value)
+{
+	writel(value, sspi->base_addr + reg);
+}
+
+static inline void sun4i_spi_drain_fifo(struct sun4i_spi *sspi, int len)
+{
+	u32 reg, cnt;
+	u8 byte;
+
+	/* See how much data is available */
+	reg = sun4i_spi_read(sspi, SUN4I_FIFO_STA_REG);
+	reg &= SUN4I_FIFO_STA_RF_CNT_MASK;
+	cnt = reg >> SUN4I_FIFO_STA_RF_CNT_BITS;
+
+	if (len > cnt)
+		len = cnt;
+
+	while (len--) {
+		byte = readb(sspi->base_addr + SUN4I_RXDATA_REG);
+		if (sspi->rx_buf)
+			*sspi->rx_buf++ = byte;
+	}
+}
+
+static inline void sun4i_spi_fill_fifo(struct sun4i_spi *sspi, int len)
+{
+	u8 byte;
+
+	if (len > sspi->len)
+		len = sspi->len;
+
+	while (len--) {
+		byte = sspi->tx_buf ? *sspi->tx_buf++ : 0;
+		writeb(byte, sspi->base_addr + SUN4I_TXDATA_REG);
+		sspi->len--;
+	}
+}
+
+static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
+{
+	struct sun4i_spi *sspi = spi_master_get_devdata(spi->master);
+	u32 reg;
+
+	reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
+
+	reg &= ~SUN4I_CTL_CS_MASK;
+	reg |= SUN4I_CTL_CS(spi->chip_select);
+
+	if (enable)
+		reg |= SUN4I_CTL_CS_LEVEL;
+	else
+		reg &= ~SUN4I_CTL_CS_LEVEL;
+
+	/*
+	 * Even though this looks irrelevant since we are supposed to
+	 * be controlling the chip select manually, this bit also
+	 * controls the levels of the chip select for inactive
+	 * devices.
+	 *
+	 * If we don't set it, the chip select level will go low by
+	 * default when the device is idle, which is not really
+	 * expected in the common case where the chip select is active
+	 * low.
+	 */
+	if (spi->mode & SPI_CS_HIGH)
+		reg &= ~SUN4I_CTL_CS_ACTIVE_LOW;
+	else
+		reg |= SUN4I_CTL_CS_ACTIVE_LOW;
+
+	sun4i_spi_write(sspi, SUN4I_CTL_REG, reg);
+}
+
+static int sun4i_spi_transfer_one(struct spi_master *master,
+				  struct spi_device *spi,
+				  struct spi_transfer *tfr)
+{
+	struct sun4i_spi *sspi = spi_master_get_devdata(master);
+	unsigned int mclk_rate, div, timeout;
+	unsigned int tx_len = 0;
+	int ret = 0;
+	u32 reg;
+
+	/* We don't support transfer larger than the FIFO */
+	if (tfr->len > SUN4I_FIFO_DEPTH)
+		return -EINVAL;
+
+	reinit_completion(&sspi->done);
+	sspi->tx_buf = tfr->tx_buf;
+	sspi->rx_buf = tfr->rx_buf;
+	sspi->len = tfr->len;
+
+	/* Clear pending interrupts */
+	sun4i_spi_write(sspi, SUN4I_INT_STA_REG, ~0);
+
+
+	reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
+
+	/* Reset FIFOs */
+	sun4i_spi_write(sspi, SUN4I_CTL_REG,
+			reg | SUN4I_CTL_RF_RST | SUN4I_CTL_TF_RST);
+
+	/*
+	 * Setup the transfer control register: Chip Select,
+	 * polarities, etc.
+	 */
+	if (spi->mode & SPI_CPOL)
+		reg |= SUN4I_CTL_CPOL;
+	else
+		reg &= ~SUN4I_CTL_CPOL;
+
+	if (spi->mode & SPI_CPHA)
+		reg |= SUN4I_CTL_CPHA;
+	else
+		reg &= ~SUN4I_CTL_CPHA;
+
+	if (spi->mode & SPI_LSB_FIRST)
+		reg |= SUN4I_CTL_LMTF;
+	else
+		reg &= ~SUN4I_CTL_LMTF;
+
+
+	/*
+	 * If it's a TX only transfer, we don't want to fill the RX
+	 * FIFO with bogus data
+	 */
+	if (sspi->rx_buf)
+		reg &= ~SUN4I_CTL_DHB;
+	else
+		reg |= SUN4I_CTL_DHB;
+
+	/* We want to control the chip select manually */
+	reg |= SUN4I_CTL_CS_MANUAL;
+
+	sun4i_spi_write(sspi, SUN4I_CTL_REG, reg);
+
+	/* Ensure that we have a parent clock fast enough */
+	mclk_rate = clk_get_rate(sspi->mclk);
+	if (mclk_rate < (2 * spi->max_speed_hz)) {
+		clk_set_rate(sspi->mclk, 2 * spi->max_speed_hz);
+		mclk_rate = clk_get_rate(sspi->mclk);
+	}
+
+	/*
+	 * Setup clock divider.
+	 *
+	 * We have two choices there. Either we can use the clock
+	 * divide rate 1, which is calculated thanks to this formula:
+	 * SPI_CLK = MOD_CLK / (2 ^ (cdr + 1))
+	 * Or we can use CDR2, which is calculated with the formula:
+	 * SPI_CLK = MOD_CLK / (2 * (cdr + 1))
+	 * Wether we use the former or the latter is set through the
+	 * DRS bit.
+	 *
+	 * First try CDR2, and if we can't reach the expected
+	 * frequency, fall back to CDR1.
+	 */
+	div = mclk_rate / (2 * spi->max_speed_hz);
+	if (div <= (SUN4I_CLK_CTL_CDR2_MASK + 1)) {
+		if (div > 0)
+			div--;
+
+		reg = SUN4I_CLK_CTL_CDR2(div) | SUN4I_CLK_CTL_DRS;
+	} else {
+		div = ilog2(mclk_rate) - ilog2(spi->max_speed_hz);
+		reg = SUN4I_CLK_CTL_CDR1(div);
+	}
+
+	sun4i_spi_write(sspi, SUN4I_CLK_CTL_REG, reg);
+
+	/* Setup the transfer now... */
+	if (sspi->tx_buf)
+		tx_len = tfr->len;
+
+	/* Setup the counters */
+	sun4i_spi_write(sspi, SUN4I_BURST_CNT_REG, SUN4I_BURST_CNT(tfr->len));
+	sun4i_spi_write(sspi, SUN4I_XMIT_CNT_REG, SUN4I_XMIT_CNT(tx_len));
+
+	/* Fill the TX FIFO */
+	sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
+
+	/* Enable the interrupts */
+	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, SUN4I_INT_CTL_TC);
+
+	/* Start the transfer */
+	reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
+	sun4i_spi_write(sspi, SUN4I_CTL_REG, reg | SUN4I_CTL_XCH);
+
+	timeout = wait_for_completion_timeout(&sspi->done,
+					      msecs_to_jiffies(1000));
+	if (!timeout) {
+		ret = -ETIMEDOUT;
+		goto out;
+	}
+
+	sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
+
+out:
+	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
+
+	return ret;
+}
+
+static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)
+{
+	struct sun4i_spi *sspi = dev_id;
+	u32 status = sun4i_spi_read(sspi, SUN4I_INT_STA_REG);
+
+	/* Transfer complete */
+	if (status & SUN4I_INT_CTL_TC) {
+		sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TC);
+		complete(&sspi->done);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int sun4i_spi_runtime_resume(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct sun4i_spi *sspi = spi_master_get_devdata(master);
+	int ret;
+
+	ret = clk_prepare_enable(sspi->hclk);
+	if (ret) {
+		dev_err(dev, "Couldn't enable AHB clock\n");
+		goto out;
+	}
+
+	ret = clk_prepare_enable(sspi->mclk);
+	if (ret) {
+		dev_err(dev, "Couldn't enable module clock\n");
+		goto err;
+	}
+
+	sun4i_spi_write(sspi, SUN4I_CTL_REG,
+			SUN4I_CTL_ENABLE | SUN4I_CTL_MASTER | SUN4I_CTL_TP);
+
+	return 0;
+
+err:
+	clk_disable_unprepare(sspi->hclk);
+out:
+	return ret;
+}
+
+static int sun4i_spi_runtime_suspend(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct sun4i_spi *sspi = spi_master_get_devdata(master);
+
+	clk_disable_unprepare(sspi->mclk);
+	clk_disable_unprepare(sspi->hclk);
+
+	return 0;
+}
+
+static int sun4i_spi_probe(struct platform_device *pdev)
+{
+	struct spi_master *master;
+	struct sun4i_spi *sspi;
+	struct resource	*res;
+	int ret = 0, irq;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(struct sun4i_spi));
+	if (!master) {
+		dev_err(&pdev->dev, "Unable to allocate SPI Master\n");
+		return -ENOMEM;
+	}
+
+	platform_set_drvdata(pdev, master);
+	sspi = spi_master_get_devdata(master);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	sspi->base_addr = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(sspi->base_addr)) {
+		ret = PTR_ERR(sspi->base_addr);
+		goto err_free_master;
+	}
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "No spi IRQ specified\n");
+		ret = -ENXIO;
+		goto err_free_master;
+	}
+
+	ret = devm_request_irq(&pdev->dev, irq, sun4i_spi_handler,
+			       0, "sun4i-spi", sspi);
+	if (ret) {
+		dev_err(&pdev->dev, "Cannot request IRQ\n");
+		goto err_free_master;
+	}
+
+	sspi->master = master;
+	master->set_cs = sun4i_spi_set_cs;
+	master->transfer_one = sun4i_spi_transfer_one;
+	master->num_chipselect = 4;
+	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST;
+	master->dev.of_node = pdev->dev.of_node;
+	master->auto_runtime_pm = true;
+
+	sspi->hclk = devm_clk_get(&pdev->dev, "ahb");
+	if (IS_ERR(sspi->hclk)) {
+		dev_err(&pdev->dev, "Unable to acquire AHB clock\n");
+		ret = PTR_ERR(sspi->hclk);
+		goto err_free_master;
+	}
+
+	sspi->mclk = devm_clk_get(&pdev->dev, "mod");
+	if (IS_ERR(sspi->mclk)) {
+		dev_err(&pdev->dev, "Unable to acquire module clock\n");
+		ret = PTR_ERR(sspi->mclk);
+		goto err_free_master;
+	}
+
+	init_completion(&sspi->done);
+
+	/*
+	 * This wake-up/shutdown pattern is to be able to have the
+	 * device woken up, even if runtime_pm is disabled
+	 */
+	ret = sun4i_spi_runtime_resume(&pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "Couldn't resume the device\n");
+		goto err_free_master;
+	}
+
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+	pm_runtime_idle(&pdev->dev);
+
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot register SPI master\n");
+		goto err_pm_disable;
+	}
+
+	return 0;
+
+err_pm_disable:
+	pm_runtime_disable(&pdev->dev);
+	sun4i_spi_runtime_suspend(&pdev->dev);
+err_free_master:
+	spi_master_put(master);
+	return ret;
+}
+
+static int sun4i_spi_remove(struct platform_device *pdev)
+{
+	pm_runtime_disable(&pdev->dev);
+
+	return 0;
+}
+
+static const struct of_device_id sun4i_spi_match[] = {
+	{ .compatible = "allwinner,sun4i-a10-spi", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, sun4i_spi_match);
+
+static const struct dev_pm_ops sun4i_spi_pm_ops = {
+	.runtime_resume		= sun4i_spi_runtime_resume,
+	.runtime_suspend	= sun4i_spi_runtime_suspend,
+};
+
+static struct platform_driver sun4i_spi_driver = {
+	.probe	= sun4i_spi_probe,
+	.remove	= sun4i_spi_remove,
+	.driver	= {
+		.name		= "sun4i-spi",
+		.owner		= THIS_MODULE,
+		.of_match_table	= sun4i_spi_match,
+		.pm		= &sun4i_spi_pm_ops,
+	},
+};
+module_platform_driver(sun4i_spi_driver);
+
+MODULE_AUTHOR("Pan Nan <pannan@allwinnertech.com>");
+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
+MODULE_DESCRIPTION("Allwinner A1X/A20 SPI controller driver");
+MODULE_LICENSE("GPL");