Re: [PATCH v2 5/6] i2c: Add Actions Semi OWL family S900 I2C driver

[Peter Rosin <peda@axentia.se>]

On June 28, 2018 8:10:41 PM GMT+02:00, Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> wrote:
>Add Actions Semi OWL family S900 I2C driver.
>
>Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
>---
> drivers/i2c/busses/Kconfig   |   7 +
> drivers/i2c/busses/Makefile  |   1 +
> drivers/i2c/busses/i2c-owl.c | 471 +++++++++++++++++++++++++++++++++++
> 3 files changed, 479 insertions(+)
> create mode 100644 drivers/i2c/busses/i2c-owl.c
>
>diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
>index 4f8df2ec87b1..2062da17e33b 100644
>--- a/drivers/i2c/busses/Kconfig
>+++ b/drivers/i2c/busses/Kconfig
>@@ -762,6 +762,13 @@ config I2C_OMAP
> 	  Like OMAP1510/1610/1710/5912 and OMAP242x.
> 	  For details see http://www.ti.com/omap.
> 
>+config I2C_OWL
>+	tristate "OWL I2C Controller"
>+	depends on ARCH_ACTIONS || COMPILE_TEST
>+	help
>+	  Say Y here if you want to use the I2C bus controller on
>+	  the Actions Semi OWL SoCs.
>+
> config I2C_PASEMI
> 	tristate "PA Semi SMBus interface"
> 	depends on PPC_PASEMI && PCI
>diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
>index 5a869144a0c5..b71618f77880 100644
>--- a/drivers/i2c/busses/Makefile
>+++ b/drivers/i2c/busses/Makefile
>@@ -76,6 +76,7 @@ obj-$(CONFIG_I2C_MXS)		+= i2c-mxs.o
> obj-$(CONFIG_I2C_NOMADIK)	+= i2c-nomadik.o
> obj-$(CONFIG_I2C_OCORES)	+= i2c-ocores.o
> obj-$(CONFIG_I2C_OMAP)		+= i2c-omap.o
>+obj-$(CONFIG_I2C_OWL)		+= i2c-owl.o
> obj-$(CONFIG_I2C_PASEMI)	+= i2c-pasemi.o
> obj-$(CONFIG_I2C_PCA_PLATFORM)	+= i2c-pca-platform.o
> obj-$(CONFIG_I2C_PMCMSP)	+= i2c-pmcmsp.o
>diff --git a/drivers/i2c/busses/i2c-owl.c
>b/drivers/i2c/busses/i2c-owl.c
>new file mode 100644
>index 000000000000..12320fca6755
>--- /dev/null
>+++ b/drivers/i2c/busses/i2c-owl.c
>@@ -0,0 +1,471 @@
>+// SPDX-License-Identifier: GPL-2.0+
>+/*
>+ * OWL SoC's I2C driver
>+ *
>+ * Copyright (c) 2014 Actions Semi Inc.
>+ * Author: David Liu <liuwei@actions-semi.com>
>+ *
>+ * Copyright (c) 2018 Linaro Ltd.
>+ * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
>+ */
>+
>+#include <linux/clk.h>
>+#include <linux/delay.h>
>+#include <linux/i2c.h>
>+#include <linux/interrupt.h>
>+#include <linux/module.h>
>+#include <linux/of_device.h>
>+#include <linux/io.h>

I would have kept this list fully sorted.

>+
>+/* I2C registers */
>+#define OWL_I2C_REG_CTL		0x0000
>+#define OWL_I2C_REG_CLKDIV	0x0004
>+#define OWL_I2C_REG_STAT	0x0008
>+#define OWL_I2C_REG_ADDR	0x000C
>+#define OWL_I2C_REG_TXDAT	0x0010
>+#define OWL_I2C_REG_RXDAT	0x0014
>+#define OWL_I2C_REG_CMD		0x0018
>+#define OWL_I2C_REG_FIFOCTL	0x001C
>+#define OWL_I2C_REG_FIFOSTAT	0x0020
>+#define OWL_I2C_REG_DATCNT	0x0024
>+#define OWL_I2C_REG_RCNT	0x0028
>+
>+/* I2Cx_CTL Bit Mask */
>+#define OWL_I2C_CTL_RB		BIT(1)
>+#define OWL_I2C_CTL_GBCC(x)	(((x) & 0x3) << 2)
>+#define	OWL_I2C_CTL_GBCC_NONE	OWL_I2C_CTL_GBCC(0)
>+#define	OWL_I2C_CTL_GBCC_START	OWL_I2C_CTL_GBCC(1)
>+#define	OWL_I2C_CTL_GBCC_STOP	OWL_I2C_CTL_GBCC(2)
>+#define	OWL_I2C_CTL_GBCC_RSTART	OWL_I2C_CTL_GBCC(3)
>+#define OWL_I2C_CTL_IRQE	BIT(5)
>+#define OWL_I2C_CTL_EN		BIT(7)
>+#define OWL_I2C_CTL_AE		BIT(8)
>+#define OWL_I2C_CTL_SHSM	BIT(10)
>+
>+#define OWL_I2C_DIV_FACTOR(x)	((x) & 0xff)
>+
>+/* I2Cx_STAT Bit Mask */
>+#define OWL_I2C_STAT_RACK	BIT(0)
>+#define OWL_I2C_STAT_BEB	BIT(1)
>+#define OWL_I2C_STAT_IRQP	BIT(2)
>+#define OWL_I2C_STAT_LAB	BIT(3)
>+#define OWL_I2C_STAT_STPD	BIT(4)
>+#define OWL_I2C_STAT_STAD	BIT(5)
>+#define OWL_I2C_STAT_BBB	BIT(6)
>+#define OWL_I2C_STAT_TCB	BIT(7)
>+#define OWL_I2C_STAT_LBST	BIT(8)
>+#define OWL_I2C_STAT_SAMB	BIT(9)
>+#define OWL_I2C_STAT_SRGC	BIT(10)
>+
>+/* I2Cx_CMD Bit Mask */
>+#define OWL_I2C_CMD_SBE		BIT(0)
>+#define OWL_I2C_CMD_RBE		BIT(4)
>+#define OWL_I2C_CMD_DE		BIT(8)
>+#define OWL_I2C_CMD_NS		BIT(9)
>+#define OWL_I2C_CMD_SE		BIT(10)
>+#define OWL_I2C_CMD_MSS		BIT(11)
>+#define OWL_I2C_CMD_WRS		BIT(12)
>+#define OWL_I2C_CMD_SECL	BIT(15)
>+
>+#define OWL_I2C_CMD_AS(x)	(((x) & 0x7) << 1)
>+#define OWL_I2C_CMD_SAS(x)	(((x) & 0x7) << 5)
>+
>+/* I2Cx_FIFOCTL Bit Mask */
>+#define OWL_I2C_FIFOCTL_NIB	BIT(0)
>+#define OWL_I2C_FIFOCTL_RFR	BIT(1)
>+#define OWL_I2C_FIFOCTL_TFR	BIT(2)
>+
>+/* I2Cc_FIFOSTAT Bit Mask */
>+#define OWL_I2C_FIFOSTAT_RNB	BIT(1)
>+#define OWL_I2C_FIFOSTAT_RFE	BIT(2)
>+#define OWL_I2C_FIFOSTAT_TFF	BIT(5)
>+#define OWL_I2C_FIFOSTAT_TFD	GENMASK(23, 16)
>+#define OWL_I2C_FIFOSTAT_RFD	GENMASK(15, 8)
>+
>+/* I2C bus timeout */
>+#define OWL_I2C_TIMEOUT		msecs_to_jiffies(4 * 1000)
>+
>+#define OWL_I2C_MAX_RETRIES	50
>+
>+#define OWL_I2C_DEFAULT_SPEED	100000
>+#define OWL_I2C_MAX_SPEED	400000
>+
>+struct owl_i2c_dev {
>+	struct i2c_adapter	adap;
>+	struct i2c_msg		*msg;
>+	struct completion	msg_complete;
>+	struct clk		*clk;
>+	void __iomem		*base;
>+	unsigned long		clk_rate;
>+	u32			bus_freq;
>+	u32			msg_ptr;
>+};
>+
>+static void owl_i2c_update_reg(void __iomem *base, unsigned int val,
>bool state)

Is base really a good name here? I would go with reg.

>+{
>+	unsigned int regval;
>+
>+	regval = readl(base);
>+
>+	if (state)
>+		regval |= val;
>+	else
>+		regval &= ~val;
>+
>+	writel(regval, base);
>+}
>+
>+static int owl_i2c_reset(struct owl_i2c_dev *i2c_dev)
>+{
>+	unsigned int val, timeout = 0;
>+
>+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
>+				OWL_I2C_CTL_EN, false);
>+	mdelay(1);
>+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
>+				OWL_I2C_CTL_EN, true);
>+
>+	/* Reset FIFO */
>+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
>+				OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR,
>+				true);
>+
>+	/* Wait 50ms for FIFO reset complete */
>+	do {
>+		val = readl(i2c_dev->base + OWL_I2C_REG_FIFOCTL);
>+		if (!(val & (OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR)))
>+			break;
>+		mdelay(1);
>+	} while (timeout++ < OWL_I2C_MAX_RETRIES);
>+
>+	if (timeout > OWL_I2C_MAX_RETRIES) {
>+		dev_err(&i2c_dev->adap.dev, "FIFO reset timeout");
>+		return -ETIMEDOUT;
>+	}
>+
>+	/* Clear status registers */
>+	writel(0, i2c_dev->base + OWL_I2C_REG_STAT);
>+
>+	return 0;
>+}

This ..._reset function does a number of unlocked read-modify-write cycles, and it is called from an interrupt. Is that safe? What if a spurious interrupt happen?

>+
>+static int owl_i2c_set_freq(struct owl_i2c_dev *i2c_dev)
>+{
>+	unsigned int val;
>+
>+	val = (i2c_dev->clk_rate + i2c_dev->bus_freq * 16 - 1) /
>+				(i2c_dev->bus_freq * 16);
>+
>+	/* Set clock divider factor */
>+	writel(OWL_I2C_DIV_FACTOR(val), i2c_dev->base + OWL_I2C_REG_CLKDIV);
>+
>+	return 0;
>+}
>+
>+static int owl_i2c_hw_init(struct owl_i2c_dev *i2c_dev)
>+{
>+	int ret;
>+
>+	/* Reset I2C controller */
>+	ret = owl_i2c_reset(i2c_dev);
>+	if (ret)
>+		return ret;
>+
>+	/* Set bus frequency */
>+	return owl_i2c_set_freq(i2c_dev);
>+}
>+
>+static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)
>+{
>+	struct owl_i2c_dev *i2c_dev = _dev;
>+	struct i2c_msg *msg = i2c_dev->msg;
>+	unsigned int stat, fifostat;
>+
>+	fifostat = readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT);
>+	if (fifostat & OWL_I2C_FIFOSTAT_RNB) {
>+		dev_dbg(&i2c_dev->adap.dev, "received NACK from device");
>+		owl_i2c_reset(i2c_dev);
>+		goto stop;
>+	}
>+
>+	stat = readl(i2c_dev->base + OWL_I2C_REG_STAT);
>+	if (stat & OWL_I2C_STAT_BEB) {
>+		dev_dbg(&i2c_dev->adap.dev, "bus error");
>+		owl_i2c_reset(i2c_dev);
>+		goto stop;
>+	}
>+
>+	/* Handle FIFO read */
>+	if (msg->flags & I2C_M_RD) {
>+		while ((readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
>+				OWL_I2C_FIFOSTAT_RFE) &&
>+				(i2c_dev->msg_ptr < msg->len)) {
>+			msg->buf[i2c_dev->msg_ptr++] = readl(i2c_dev->base +
>+							OWL_I2C_REG_RXDAT);
>+		}
>+	} else {
>+		/* Handle the remaining bytes which were not sent */
>+		while (!(readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
>+				OWL_I2C_FIFOSTAT_TFF) &&
>+				i2c_dev->msg_ptr < msg->len) {
>+			writel(msg->buf[i2c_dev->msg_ptr++], i2c_dev->base +
>+							OWL_I2C_REG_TXDAT);
>+		}
>+	}
>+
>+stop:
>+	/* Clear pending interrupts */
>+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_STAT,
>+				OWL_I2C_STAT_IRQP, true);
>+
>+	complete_all(&i2c_dev->msg_complete);
>+
>+	return IRQ_HANDLED;
>+}
>+
>+static u32 owl_i2c_func(struct i2c_adapter *adap)
>+{
>+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
>+}
>+
>+static int owl_i2c_check_bus_busy(struct i2c_adapter *adap)
>+{
>+	struct owl_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
>+	unsigned long timeout;
>+	unsigned int val;
>+
>+	/* Check for Arbitration lost */
>+	val = readl(i2c_dev->base + OWL_I2C_REG_STAT);
>+	if (val & OWL_I2C_STAT_LAB) {
>+		val &= ~OWL_I2C_STAT_LAB;
>+		writel(val, i2c_dev->base + OWL_I2C_REG_STAT);
>+		return -EAGAIN;
>+	}
>+
>+	/* Check for Bus busy */
>+	timeout = jiffies + OWL_I2C_TIMEOUT;
>+	while (readl(i2c_dev->base + OWL_I2C_REG_STAT) & OWL_I2C_STAT_BBB) {
>+		if (time_after(jiffies, timeout)) {
>+			dev_err(&adap->dev, "Bus busy timeout");
>+			return -ETIMEDOUT;
>+		}
>+	}
>+
>+	return 0;
>+}
>+
>+static int owl_i2c_master_xfer(struct i2c_adapter *adap, struct
>i2c_msg *msgs,
>+				int num)
>+{
>+	struct owl_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
>+	struct i2c_msg *msg;
>+	unsigned long time_left;
>+	unsigned int i2c_cmd;
>+	unsigned int addr;
>+	int ret = 0, idx;
>+
>+	ret = owl_i2c_hw_init(i2c_dev);
>+	if (ret)
>+		return ret;
>+
>+	ret = owl_i2c_check_bus_busy(adap);
>+	if (ret)
>+		return ret;
>+
>+	reinit_completion(&i2c_dev->msg_complete);
>+
>+	/* Enable I2C controller interrupt */
>+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
>+				OWL_I2C_CTL_IRQE, true);
>+
>+	/*
>+	 * Select: FIFO enable, Master mode, Stop enable, Data count enable,
>+	 * Send start bit
>+	 */
>+	i2c_cmd = (OWL_I2C_CMD_SECL | OWL_I2C_CMD_MSS | OWL_I2C_CMD_SE
>+			| OWL_I2C_CMD_NS | OWL_I2C_CMD_DE | OWL_I2C_CMD_SBE);
>+
>+	/* Handle repeated start condition */
>+	if (num > 1) {
>+		/* Set internal address length and enable repeated start */
>+		i2c_cmd |= (OWL_I2C_CMD_AS(msgs[0].len + 1)
>+				| OWL_I2C_CMD_SAS(1) | OWL_I2C_CMD_RBE);
>+
>+		/* Write slave address */
>+		addr = i2c_8bit_addr_from_msg(&msgs[0]);
>+		writel(addr, i2c_dev->base + OWL_I2C_REG_TXDAT);
>+
>+		/* Write internal register address */
>+		for (idx = 0; idx < msgs[0].len; idx++)
>+			writel(msgs[0].buf[idx], i2c_dev->base +
>+						OWL_I2C_REG_TXDAT);
>+
>+		msg = &msgs[1];
>+	} else {
>+		/* Set address length */
>+		i2c_cmd |= OWL_I2C_CMD_AS(1);
>+		msg = &msgs[0];
>+	}
>+
>+	i2c_dev->msg = msg;
>+	i2c_dev->msg_ptr = 0;
>+
>+	/* Set data count for the message */
>+	writel(msg->len, i2c_dev->base + OWL_I2C_REG_DATCNT);
>+
>+	addr = i2c_8bit_addr_from_msg(msg);
>+	writel(addr, i2c_dev->base + OWL_I2C_REG_TXDAT);
>+
>+	if (!(msg->flags & I2C_M_RD)) {
>+		/* Write data to FIFO */
>+		for (idx = 0; idx < msg->len; idx++) {
>+			/* Check for FIFO full */
>+			if (readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT)
>+					& OWL_I2C_FIFOSTAT_TFF)

You should cleanup here, and return some error. I think? Or, why do you break out of the loop early?

>+				break;
>+
>+			writel(msg->buf[idx],
>+					i2c_dev->base + OWL_I2C_REG_TXDAT);
>+		}
>+
>+		i2c_dev->msg_ptr = idx;
>+	}
>+
>+	/* Ignore the NACK if needed */
>+	if (msg->flags & I2C_M_IGNORE_NAK)
>+		owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
>+				OWL_I2C_FIFOCTL_NIB, true);
>+	else
>+		owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
>+				OWL_I2C_FIFOCTL_NIB, false);
>+
>+	/* Start the transfer */
>+	writel(i2c_cmd, i2c_dev->base + OWL_I2C_REG_CMD);
>+
>+	time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
>+						adap->timeout);
>+	if (time_left == 0) {
>+		dev_err(&adap->dev, "Transaction timed out");
>+		/* Send stop condition and release the bus */
>+		owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
>+			OWL_I2C_CTL_GBCC_STOP | OWL_I2C_CTL_RB, true);
>+		ret = -ETIMEDOUT;
>+	}
>+
>+	/* Disable I2C controller */
>+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
>+				OWL_I2C_CTL_EN, false);
>+
>+	return i2c_dev->msg_ptr ? num : i2c_dev->msg_ptr;

This is wrong. Should probably be

   return ret ?: num;

Cheers,
Peter

>+}
>+
>+static const struct i2c_algorithm owl_i2c_algorithm = {
>+	.master_xfer    = owl_i2c_master_xfer,
>+	.functionality  = owl_i2c_func
>+};
>+
>+static const struct i2c_adapter_quirks owl_i2c_quirks = {
>+	.flags		= I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST,
>+	.max_read_len   = 240,
>+	.max_write_len  = 240,
>+	.max_comb_1st_msg_len = 6,
>+	.max_comb_2nd_msg_len = 240
>+};
>+
>+static int owl_i2c_probe(struct platform_device *pdev)
>+{
>+	struct device *dev = &pdev->dev;
>+	struct owl_i2c_dev *i2c_dev;
>+	struct resource *res;
>+	int ret, irq;
>+
>+	i2c_dev = devm_kzalloc(dev, sizeof(*i2c_dev), GFP_KERNEL);
>+	if (!i2c_dev)
>+		return -ENOMEM;
>+
>+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>+	i2c_dev->base = devm_ioremap_resource(dev, res);
>+	if (IS_ERR(i2c_dev->base))
>+		return PTR_ERR(i2c_dev->base);
>+
>+	irq = platform_get_irq(pdev, 0);
>+	if (irq < 0) {
>+		dev_err(dev, "failed to get IRQ number\n");
>+		return irq;
>+	}
>+
>+	if (of_property_read_u32(dev->of_node, "clock-frequency",
>+					&i2c_dev->bus_freq))
>+		i2c_dev->bus_freq = OWL_I2C_DEFAULT_SPEED;
>+
>+	/* We support only frequencies of 100k and 400k for now */
>+	if (i2c_dev->bus_freq != OWL_I2C_DEFAULT_SPEED &&
>+			i2c_dev->bus_freq > OWL_I2C_MAX_SPEED) {
>+		dev_err(dev, "invalid clock-frequency %d\n", i2c_dev->bus_freq);
>+		return -EINVAL;
>+	}
>+
>+	i2c_dev->clk = devm_clk_get(dev, NULL);
>+	if (IS_ERR(i2c_dev->clk)) {
>+		dev_err(dev, "failed to get clock\n");
>+		return PTR_ERR(i2c_dev->clk);
>+	}
>+
>+	ret = clk_prepare_enable(i2c_dev->clk);
>+	if (ret)
>+		return ret;
>+
>+	i2c_dev->clk_rate = clk_get_rate(i2c_dev->clk);
>+	if (!i2c_dev->clk_rate) {
>+		dev_err(dev, "input clock rate should not be zero\n");
>+		ret = -EINVAL;
>+		goto disable_clk;
>+	}
>+
>+	init_completion(&i2c_dev->msg_complete);
>+	i2c_dev->adap.owner = THIS_MODULE;
>+	i2c_dev->adap.algo = &owl_i2c_algorithm;
>+	i2c_dev->adap.timeout = OWL_I2C_TIMEOUT;
>+	i2c_dev->adap.quirks = &owl_i2c_quirks;
>+	i2c_dev->adap.dev.parent = dev;
>+	i2c_dev->adap.dev.of_node = dev->of_node;
>+	snprintf(i2c_dev->adap.name, sizeof(i2c_dev->adap.name),
>+			"%s", "OWL I2C adapter");
>+	i2c_set_adapdata(&i2c_dev->adap, i2c_dev);
>+
>+	platform_set_drvdata(pdev, i2c_dev);
>+
>+	ret = devm_request_irq(dev, irq, owl_i2c_interrupt, 0, pdev->name,
>+				i2c_dev);
>+	if (ret) {
>+		dev_err(dev, "failed to request irq %d\n", irq);
>+		goto disable_clk;
>+	}
>+
>+	return i2c_add_adapter(&i2c_dev->adap);
>+
>+disable_clk:
>+	clk_disable_unprepare(i2c_dev->clk);
>+
>+	return ret;
>+}
>+
>+static const struct of_device_id owl_i2c_of_match[] = {
>+	{.compatible = "actions,s900-i2c"},
>+	{ /* sentinel */ }
>+};
>+MODULE_DEVICE_TABLE(of, owl_i2c_of_match);
>+
>+static struct platform_driver owl_i2c_driver = {
>+	.probe		= owl_i2c_probe,
>+	.driver		= {
>+		.name	= "owl-i2c",
>+		.of_match_table = of_match_ptr(owl_i2c_of_match),
>+	},
>+};
>+module_platform_driver(owl_i2c_driver);
>+
>+MODULE_AUTHOR("David Liu <liuwei@actions-semi.com>");
>+MODULE_AUTHOR("Manivannan Sadhasivam
><manivannan.sadhasivam@linaro.org>");
>+MODULE_DESCRIPTION("Actions Semi OWL SoCs I2C driver");
>+MODULE_LICENSE("GPL");