[PATCH v2 2/4] i2c: add stm32f7 I2C adapter driver

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

This patch adds initial support for the STM32F7 I2C controller.
It was tested to work with the STM32MP157C.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/i2c/busses/Kconfig     |   5 +
 drivers/i2c/busses/Makefile    |   1 +
 drivers/i2c/busses/i2c-stm32.c | 863 +++++++++++++++++++++++++++++++++
 3 files changed, 869 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-stm32.c

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 2e47cdb491f6..21d2cb21cf5a 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -55,4 +55,9 @@ config I2C_VERSATILE
 	  Say yes if you want to support the I2C serial bus on ARMs Versatile
 	  range of platforms.
 
+config I2C_STM32
+	bool "STM32 I2C master driver"
+	select RESET_CONTROLLER
+	depends on HAVE_CLK
+
 endmenu
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 61d7c86e7692..7e450ead2738 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_I2C_OMAP)		+= i2c-omap.o
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
 obj-$(CONFIG_I2C_DESIGNWARE)	+= i2c-designware.o
+obj-$(CONFIG_I2C_STM32)		+= i2c-stm32.o
diff --git a/drivers/i2c/busses/i2c-stm32.c b/drivers/i2c/busses/i2c-stm32.c
new file mode 100644
index 000000000000..6af55fb3ffda
--- /dev/null
+++ b/drivers/i2c/busses/i2c-stm32.c
@@ -0,0 +1,863 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2017 STMicroelectronics
+ * Copyright 2019 Ahmad Fatoum, Pengutronix
+ */
+
+#define pr_fmt(fmt) "i2c-stm32: " fmt
+
+#include <common.h>
+#include <i2c/i2c.h>
+#include <init.h>
+#include <linux/clk.h>
+#include <linux/iopoll.h>
+#include <linux/reset.h>
+
+/* STM32 I2C registers */
+struct __packed stm32_i2c_regs {
+	u32 cr1;	/* I2C control register 1 */
+	u32 cr2;	/* I2C control register 2 */
+	u32 oar1;	/* I2C own address 1 register */
+	u32 oar2;	/* I2C own address 2 register */
+	u32 timingr;	/* I2C timing register */
+	u32 timeoutr;	/* I2C timeout register */
+	u32 isr;	/* I2C interrupt and status register */
+	u32 icr;	/* I2C interrupt clear register */
+	u32 pecr;	/* I2C packet error checking register */
+	u32 rxdr;	/* I2C receive data register */
+	u32 txdr;	/* I2C transmit data register */
+};
+
+#define STM32_I2C_CR1				0x00
+#define STM32_I2C_CR2				0x04
+#define STM32_I2C_TIMINGR			0x10
+#define STM32_I2C_ISR				0x18
+#define STM32_I2C_ICR				0x1C
+#define STM32_I2C_RXDR				0x24
+#define STM32_I2C_TXDR				0x28
+
+/* STM32 I2C control 1 */
+#define STM32_I2C_CR1_ANFOFF			BIT(12)
+#define STM32_I2C_CR1_ERRIE			BIT(7)
+#define STM32_I2C_CR1_TCIE			BIT(6)
+#define STM32_I2C_CR1_STOPIE			BIT(5)
+#define STM32_I2C_CR1_NACKIE			BIT(4)
+#define STM32_I2C_CR1_ADDRIE			BIT(3)
+#define STM32_I2C_CR1_RXIE			BIT(2)
+#define STM32_I2C_CR1_TXIE			BIT(1)
+#define STM32_I2C_CR1_PE			BIT(0)
+
+/* STM32 I2C control 2 */
+#define STM32_I2C_CR2_AUTOEND			BIT(25)
+#define STM32_I2C_CR2_RELOAD			BIT(24)
+#define STM32_I2C_CR2_NBYTES_MASK		GENMASK(23, 16)
+#define STM32_I2C_CR2_NBYTES(n)			((n & 0xff) << 16)
+#define STM32_I2C_CR2_NACK			BIT(15)
+#define STM32_I2C_CR2_STOP			BIT(14)
+#define STM32_I2C_CR2_START			BIT(13)
+#define STM32_I2C_CR2_HEAD10R			BIT(12)
+#define STM32_I2C_CR2_ADD10			BIT(11)
+#define STM32_I2C_CR2_RD_WRN			BIT(10)
+#define STM32_I2C_CR2_SADD10_MASK		GENMASK(9, 0)
+#define STM32_I2C_CR2_SADD10(n)			(n & STM32_I2C_CR2_SADD10_MASK)
+#define STM32_I2C_CR2_SADD7_MASK		GENMASK(7, 1)
+#define STM32_I2C_CR2_SADD7(n)			((n & 0x7f) << 1)
+#define STM32_I2C_CR2_RESET_MASK		(STM32_I2C_CR2_HEAD10R \
+						| STM32_I2C_CR2_NBYTES_MASK \
+						| STM32_I2C_CR2_SADD7_MASK \
+						| STM32_I2C_CR2_RELOAD \
+						| STM32_I2C_CR2_RD_WRN)
+
+/* STM32 I2C Interrupt Status */
+#define STM32_I2C_ISR_BUSY			BIT(15)
+#define STM32_I2C_ISR_ARLO			BIT(9)
+#define STM32_I2C_ISR_BERR			BIT(8)
+#define STM32_I2C_ISR_TCR			BIT(7)
+#define STM32_I2C_ISR_TC			BIT(6)
+#define STM32_I2C_ISR_STOPF			BIT(5)
+#define STM32_I2C_ISR_NACKF			BIT(4)
+#define STM32_I2C_ISR_ADDR			BIT(3)
+#define STM32_I2C_ISR_RXNE			BIT(2)
+#define STM32_I2C_ISR_TXIS			BIT(1)
+#define STM32_I2C_ISR_TXE			BIT(0)
+#define STM32_I2C_ISR_ERRORS			(STM32_I2C_ISR_BERR \
+						| STM32_I2C_ISR_ARLO)
+
+/* STM32 I2C Interrupt Clear */
+#define STM32_I2C_ICR_ARLOCF			BIT(9)
+#define STM32_I2C_ICR_BERRCF			BIT(8)
+#define STM32_I2C_ICR_STOPCF			BIT(5)
+#define STM32_I2C_ICR_NACKCF			BIT(4)
+
+/* STM32 I2C Timing */
+#define STM32_I2C_TIMINGR_PRESC(n)		((n & 0xf) << 28)
+#define STM32_I2C_TIMINGR_SCLDEL(n)		((n & 0xf) << 20)
+#define STM32_I2C_TIMINGR_SDADEL(n)		((n & 0xf) << 16)
+#define STM32_I2C_TIMINGR_SCLH(n)		((n & 0xff) << 8)
+#define STM32_I2C_TIMINGR_SCLL(n)		(n & 0xff)
+
+#define STM32_I2C_MAX_LEN			0xff
+
+#define STM32_I2C_DNF_DEFAULT			0
+#define STM32_I2C_DNF_MAX			16
+
+#define STM32_I2C_ANALOG_FILTER_ENABLE	1
+#define STM32_I2C_ANALOG_FILTER_DELAY_MIN	50	/* ns */
+#define STM32_I2C_ANALOG_FILTER_DELAY_MAX	260	/* ns */
+
+#define STM32_I2C_RISE_TIME_DEFAULT		25	/* ns */
+#define STM32_I2C_FALL_TIME_DEFAULT		10	/* ns */
+
+#define STM32_PRESC_MAX				BIT(4)
+#define STM32_SCLDEL_MAX			BIT(4)
+#define STM32_SDADEL_MAX			BIT(4)
+#define STM32_SCLH_MAX				BIT(8)
+#define STM32_SCLL_MAX				BIT(8)
+
+#define STANDARD_RATE				100000
+#define FAST_RATE				400000
+#define FAST_PLUS_RATE				1000000
+
+enum stm32_i2c_speed {
+	STM32_I2C_SPEED_STANDARD, /* 100 kHz */
+	STM32_I2C_SPEED_FAST, /* 400 kHz */
+	STM32_I2C_SPEED_FAST_PLUS, /* 1 MHz */
+	STM32_I2C_SPEED_END,
+};
+
+/**
+ * struct stm32_i2c_spec - private i2c specification timing
+ * @rate: I2C bus speed (Hz)
+ * @rate_min: 80% of I2C bus speed (Hz)
+ * @rate_max: 120% of I2C bus speed (Hz)
+ * @fall_max: Max fall time of both SDA and SCL signals (ns)
+ * @rise_max: Max rise time of both SDA and SCL signals (ns)
+ * @hddat_min: Min data hold time (ns)
+ * @vddat_max: Max data valid time (ns)
+ * @sudat_min: Min data setup time (ns)
+ * @l_min: Min low period of the SCL clock (ns)
+ * @h_min: Min high period of the SCL clock (ns)
+ */
+
+struct stm32_i2c_spec {
+	u32 rate;
+	u32 rate_min;
+	u32 rate_max;
+	u32 fall_max;
+	u32 rise_max;
+	u32 hddat_min;
+	u32 vddat_max;
+	u32 sudat_min;
+	u32 l_min;
+	u32 h_min;
+};
+
+/**
+ * struct stm32_i2c_setup - private I2C timing setup parameters
+ * @speed: I2C speed mode (standard, Fast Plus)
+ * @speed_freq: actual I2C speed frequency  (Hz)
+ * @clock_src: I2C clock source frequency (Hz)
+ * @dnf: Digital filter coefficient (0-16)
+ * @analog_filter: Analog filter delay (On/Off)
+ * @timings: I2C timings parameters
+ */
+struct stm32_i2c_setup {
+	enum stm32_i2c_speed speed;
+	u32 speed_freq;
+	u32 clock_src;
+	u8 dnf;
+	bool analog_filter;
+	struct i2c_timings timings;
+};
+
+/**
+ * struct stm32_i2c_timings - private I2C output parameters
+ * @prec: Prescaler value
+ * @scldel: Data setup time
+ * @sdadel: Data hold time
+ * @sclh: SCL high period (master mode)
+ * @sclh: SCL low period (master mode)
+ */
+struct stm32_i2c_timings {
+	struct list_head node;
+	u8 presc;
+	u8 scldel;
+	u8 sdadel;
+	u8 sclh;
+	u8 scll;
+};
+
+static const struct stm32_i2c_spec i2c_specs[] = {
+	[STM32_I2C_SPEED_STANDARD] = {
+		.rate = STANDARD_RATE,
+		.rate_min = 8000,
+		.rate_max = 120000,
+		.fall_max = 300,
+		.rise_max = 1000,
+		.hddat_min = 0,
+		.vddat_max = 3450,
+		.sudat_min = 250,
+		.l_min = 4700,
+		.h_min = 4000,
+	},
+	[STM32_I2C_SPEED_FAST] = {
+		.rate = FAST_RATE,
+		.rate_min = 320000,
+		.rate_max = 480000,
+		.fall_max = 300,
+		.rise_max = 300,
+		.hddat_min = 0,
+		.vddat_max = 900,
+		.sudat_min = 100,
+		.l_min = 1300,
+		.h_min = 600,
+	},
+	[STM32_I2C_SPEED_FAST_PLUS] = {
+		.rate = FAST_PLUS_RATE,
+		.rate_min = 800000,
+		.rate_max = 1200000,
+		.fall_max = 100,
+		.rise_max = 120,
+		.hddat_min = 0,
+		.vddat_max = 450,
+		.sudat_min = 50,
+		.l_min = 500,
+		.h_min = 260,
+	},
+};
+
+struct stm32_i2c {
+	struct stm32_i2c_regs __iomem *regs;
+	struct clk *clk;
+	struct i2c_adapter adapter;
+	struct stm32_i2c_setup setup;
+};
+#define to_stm32_i2c(a)	container_of(a, struct stm32_i2c, adapter)
+
+static inline int stm32_i2c_check_device_busy(struct stm32_i2c *priv)
+{
+	u32 status = readl(&priv->regs->isr);
+	return status & STM32_I2C_ISR_BUSY;
+}
+
+static void stm32_i2c_message_start(struct stm32_i2c *i2c_priv,
+				    struct i2c_msg *msg, bool stop)
+{
+	struct stm32_i2c_regs *regs = i2c_priv->regs;
+	u32 cr2 = readl(&regs->cr2);
+
+	/* Set transfer direction */
+	cr2 &= ~STM32_I2C_CR2_RD_WRN;
+	if (msg->flags & I2C_M_RD)
+		cr2 |= STM32_I2C_CR2_RD_WRN;
+
+	/* Set slave address */
+	cr2 &= ~(STM32_I2C_CR2_HEAD10R | STM32_I2C_CR2_ADD10);
+	if (msg->flags & I2C_M_TEN) {
+		cr2 &= ~STM32_I2C_CR2_SADD10_MASK;
+		cr2 |= STM32_I2C_CR2_SADD10(msg->addr);
+		cr2 |= STM32_I2C_CR2_ADD10;
+	} else {
+		cr2 &= ~STM32_I2C_CR2_SADD7_MASK;
+		cr2 |= STM32_I2C_CR2_SADD7(msg->addr);
+	}
+
+	/* Set nb bytes to transfer and reload or autoend bits */
+	cr2 &= ~(STM32_I2C_CR2_NBYTES_MASK | STM32_I2C_CR2_RELOAD |
+		 STM32_I2C_CR2_AUTOEND);
+	if (msg->len > STM32_I2C_MAX_LEN) {
+		cr2 |= STM32_I2C_CR2_NBYTES(STM32_I2C_MAX_LEN);
+		cr2 |= STM32_I2C_CR2_RELOAD;
+	} else {
+		cr2 |= STM32_I2C_CR2_NBYTES(msg->len);
+	}
+
+	/* Write configurations register */
+	writel(cr2, &regs->cr2);
+
+	/* START/ReSTART generation */
+	setbits_le32(&regs->cr2, STM32_I2C_CR2_START);
+}
+
+/*
+ * RELOAD mode must be selected if total number of data bytes to be
+ * sent is greater than MAX_LEN
+ */
+
+static void stm32_i2c_handle_reload(struct stm32_i2c *i2c_priv,
+				    struct i2c_msg *msg, bool stop)
+{
+	struct stm32_i2c_regs *regs = i2c_priv->regs;
+	u32 cr2 = readl(&regs->cr2);
+
+	cr2 &= ~STM32_I2C_CR2_NBYTES_MASK;
+
+	if (msg->len > STM32_I2C_MAX_LEN) {
+		cr2 |= STM32_I2C_CR2_NBYTES(STM32_I2C_MAX_LEN);
+	} else {
+		cr2 &= ~STM32_I2C_CR2_RELOAD;
+		cr2 |= STM32_I2C_CR2_NBYTES(msg->len);
+	}
+
+	writel(cr2, &regs->cr2);
+}
+
+static int stm32_i2c_wait_flags(struct stm32_i2c *i2c_priv,
+				u32 flags, u32 *status)
+{
+	struct stm32_i2c_regs *regs = i2c_priv->regs;
+
+	return readl_poll_timeout(&regs->isr, *status,
+				  *status & flags, USEC_PER_SEC);
+}
+
+static int stm32_i2c_check_end_of_message(struct stm32_i2c *i2c_priv)
+{
+	struct stm32_i2c_regs *regs = i2c_priv->regs;
+	u32 mask = STM32_I2C_ISR_ERRORS | STM32_I2C_ISR_NACKF |
+		   STM32_I2C_ISR_STOPF;
+	struct device_d *dev = &i2c_priv->adapter.dev;
+	u32 status;
+	int ret;
+
+	ret = stm32_i2c_wait_flags(i2c_priv, mask, &status);
+	if (ret)
+		return ret;
+
+	if (status & STM32_I2C_ISR_BERR) {
+		dev_dbg(dev, "Bus error\n");
+
+		/* Clear BERR flag */
+		setbits_le32(&regs->icr, STM32_I2C_ICR_BERRCF);
+
+		return -EIO;
+	}
+
+	if (status & STM32_I2C_ISR_ARLO) {
+		dev_dbg(dev, "Arbitration lost\n");
+
+		/* Clear ARLO flag */
+		setbits_le32(&regs->icr, STM32_I2C_ICR_ARLOCF);
+
+		return -EAGAIN;
+	}
+
+	if (status & STM32_I2C_ISR_NACKF) {
+		dev_dbg(dev, "Receive NACK\n");
+
+		/* Clear NACK flag */
+		setbits_le32(&regs->icr, STM32_I2C_ICR_NACKCF);
+
+		/* Wait until STOPF flag is set */
+		mask = STM32_I2C_ISR_STOPF;
+		ret = stm32_i2c_wait_flags(i2c_priv, mask, &status);
+		if (ret)
+			return ret;
+
+		ret = -EIO;
+	}
+
+	if (status & STM32_I2C_ISR_STOPF) {
+		/* Clear STOP flag */
+		setbits_le32(&regs->icr, STM32_I2C_ICR_STOPCF);
+
+		/* Clear control register 2 */
+		setbits_le32(&regs->cr2, STM32_I2C_CR2_RESET_MASK);
+	}
+
+	return ret;
+}
+
+static int stm32_i2c_message_xfer(struct stm32_i2c *i2c_priv,
+				  struct i2c_msg *msg, bool stop)
+{
+	struct stm32_i2c_regs *regs = i2c_priv->regs;
+	int len = msg->len;
+	u8 *buf = msg->buf;
+	u32 status;
+	u32 mask = msg->flags & I2C_M_RD ? STM32_I2C_ISR_RXNE :
+		   STM32_I2C_ISR_TXIS | STM32_I2C_ISR_NACKF;
+	int bytes_to_rw = min(len, STM32_I2C_MAX_LEN);
+	int ret = 0;
+
+	/* Add errors */
+	mask |= STM32_I2C_ISR_ERRORS;
+
+	stm32_i2c_message_start(i2c_priv, msg, stop);
+
+	while (len) {
+		/*
+		 * Wait until TXIS/NACKF/BERR/ARLO flags or
+		 * RXNE/BERR/ARLO flags are set
+		 */
+		ret = stm32_i2c_wait_flags(i2c_priv, mask, &status);
+		if (ret)
+			break;
+
+		if (status & (STM32_I2C_ISR_NACKF | STM32_I2C_ISR_ERRORS))
+			break;
+
+		if (status & STM32_I2C_ISR_RXNE) {
+			*buf++ = readb(&regs->rxdr);
+			len--;
+			bytes_to_rw--;
+		}
+
+		if (status & STM32_I2C_ISR_TXIS) {
+			writeb(*buf++, &regs->txdr);
+			len--;
+			bytes_to_rw--;
+		}
+
+		if (!bytes_to_rw && len) {
+			/* Wait until TCR flag is set */
+			mask = STM32_I2C_ISR_TCR;
+			ret = stm32_i2c_wait_flags(i2c_priv, mask, &status);
+			if (ret)
+				break;
+
+			bytes_to_rw = min(len, STM32_I2C_MAX_LEN);
+			mask = msg->flags & I2C_M_RD ? STM32_I2C_ISR_RXNE :
+			       STM32_I2C_ISR_TXIS | STM32_I2C_ISR_NACKF;
+
+			stm32_i2c_handle_reload(i2c_priv, msg, stop);
+		} else if (!bytes_to_rw) {
+			/* Wait until TC flag is set */
+			mask = STM32_I2C_ISR_TC;
+			ret = stm32_i2c_wait_flags(i2c_priv, mask, &status);
+			if (ret)
+				break;
+
+			if (!stop)
+				/* Message sent, new message has to be sent */
+				return 0;
+		}
+	}
+
+	/* End of transfer, send stop condition */
+	mask = STM32_I2C_CR2_STOP;
+	setbits_le32(&regs->cr2, mask);
+
+	return stm32_i2c_check_end_of_message(i2c_priv);
+}
+
+static int stm32_i2c_xfer(struct i2c_adapter *adapter,
+			  struct i2c_msg *msg, int nmsgs)
+{
+	struct stm32_i2c *i2c_priv = to_stm32_i2c(adapter);
+	int ret;
+	int i;
+
+	ret = stm32_i2c_check_device_busy(i2c_priv);
+	if (ret)
+		return -EBUSY;
+
+	for (i = 0; i < nmsgs; i++) {
+		ret = stm32_i2c_message_xfer(i2c_priv, &msg[i], i == nmsgs - 1);
+		if (ret)
+			return ret;
+	}
+
+	return nmsgs;
+}
+
+
+static int stm32_i2c_compute_solutions(struct stm32_i2c_setup *setup,
+				       struct list_head *solutions)
+{
+	struct stm32_i2c_timings *v;
+	u32 p_prev = STM32_PRESC_MAX;
+	u32 i2cclk = DIV_ROUND_CLOSEST(NSEC_PER_SEC, setup->clock_src);
+	u32 af_delay_min = 0, af_delay_max = 0;
+	u16 p, l, a;
+	int sdadel_min, sdadel_max, scldel_min;
+	int ret = 0;
+
+	if (setup->analog_filter) {
+		af_delay_min = STM32_I2C_ANALOG_FILTER_DELAY_MIN;
+		af_delay_max = STM32_I2C_ANALOG_FILTER_DELAY_MAX;
+	}
+
+	sdadel_min = i2c_specs[setup->speed].hddat_min + setup->timings.scl_fall_ns -
+		     af_delay_min - (setup->dnf + 3) * i2cclk;
+
+	sdadel_max = i2c_specs[setup->speed].vddat_max - setup->timings.scl_rise_ns -
+		     af_delay_max - (setup->dnf + 4) * i2cclk;
+
+	scldel_min = setup->timings.scl_rise_ns + i2c_specs[setup->speed].sudat_min;
+
+	if (sdadel_min < 0)
+		sdadel_min = 0;
+	if (sdadel_max < 0)
+		sdadel_max = 0;
+
+	pr_debug("SDADEL(min/max): %i/%i, SCLDEL(Min): %i\n",
+		 sdadel_min, sdadel_max, scldel_min);
+
+	/* Compute possible values for PRESC, SCLDEL and SDADEL */
+	for (p = 0; p < STM32_PRESC_MAX; p++) {
+		for (l = 0; l < STM32_SCLDEL_MAX; l++) {
+			u32 scldel = (l + 1) * (p + 1) * i2cclk;
+
+			if (scldel < scldel_min)
+				continue;
+
+			for (a = 0; a < STM32_SDADEL_MAX; a++) {
+				u32 sdadel = (a * (p + 1) + 1) * i2cclk;
+
+				if (((sdadel >= sdadel_min) &&
+				     (sdadel <= sdadel_max)) &&
+				    (p != p_prev)) {
+					v = calloc(1, sizeof(*v));
+					if (!v)
+						return -ENOMEM;
+
+					v->presc = p;
+					v->scldel = l;
+					v->sdadel = a;
+					p_prev = p;
+
+					list_add_tail(&v->node, solutions);
+					break;
+				}
+			}
+
+			if (p_prev == p)
+				break;
+		}
+	}
+
+	if (list_empty(solutions))
+		ret = -EPERM;
+
+	return ret;
+}
+
+static int stm32_i2c_choose_solution(struct stm32_i2c_setup *setup,
+				     struct list_head *solutions,
+				     struct stm32_i2c_timings *s)
+{
+	struct stm32_i2c_timings *v;
+	u32 i2cbus = DIV_ROUND_CLOSEST(NSEC_PER_SEC, setup->speed_freq);
+	u32 clk_error_prev = i2cbus;
+	u32 i2cclk = DIV_ROUND_CLOSEST(NSEC_PER_SEC, setup->clock_src);
+	u32 clk_min, clk_max;
+	u32 af_delay_min = 0;
+	u32 dnf_delay;
+	u32 tsync;
+	u16 l, h;
+	bool sol_found = false;
+	int ret = 0;
+
+	if (setup->analog_filter)
+		af_delay_min = STM32_I2C_ANALOG_FILTER_DELAY_MIN;
+
+	dnf_delay = setup->dnf * i2cclk;
+
+	tsync = af_delay_min + dnf_delay + (2 * i2cclk);
+	clk_max = NSEC_PER_SEC / i2c_specs[setup->speed].rate_min;
+	clk_min = NSEC_PER_SEC / i2c_specs[setup->speed].rate_max;
+
+	/*
+	 * Among Prescaler possibilities discovered above figures out SCL Low
+	 * and High Period. Provided:
+	 * - SCL Low Period has to be higher than Low Period of the SCL Clock
+	 *   defined by I2C Specification. I2C Clock has to be lower than
+	 *   (SCL Low Period - Analog/Digital filters) / 4.
+	 * - SCL High Period has to be lower than High Period of the SCL Clock
+	 *   defined by I2C Specification
+	 * - I2C Clock has to be lower than SCL High Period
+	 */
+	list_for_each_entry(v, solutions, node) {
+		u32 prescaler = (v->presc + 1) * i2cclk;
+
+		for (l = 0; l < STM32_SCLL_MAX; l++) {
+			u32 tscl_l = (l + 1) * prescaler + tsync;
+
+			if ((tscl_l < i2c_specs[setup->speed].l_min) ||
+			    (i2cclk >=
+			     ((tscl_l - af_delay_min - dnf_delay) / 4))) {
+				continue;
+			}
+
+			for (h = 0; h < STM32_SCLH_MAX; h++) {
+				u32 tscl_h = (h + 1) * prescaler + tsync;
+				u32 tscl = tscl_l + tscl_h +
+					   setup->timings.scl_rise_ns +
+					   setup->timings.scl_fall_ns;
+
+				if ((tscl >= clk_min) && (tscl <= clk_max) &&
+				    (tscl_h >= i2c_specs[setup->speed].h_min) &&
+				    (i2cclk < tscl_h)) {
+					int clk_error = tscl - i2cbus;
+
+					if (clk_error < 0)
+						clk_error = -clk_error;
+
+					if (clk_error < clk_error_prev) {
+						clk_error_prev = clk_error;
+						v->scll = l;
+						v->sclh = h;
+						sol_found = true;
+						memcpy(s, v, sizeof(*s));
+					}
+				}
+			}
+		}
+	}
+
+	if (!sol_found)
+		ret = -EPERM;
+
+	return ret;
+}
+
+static int stm32_i2c_compute_timing(struct stm32_i2c *i2c_priv,
+				    struct stm32_i2c_setup *setup,
+				    struct stm32_i2c_timings *output)
+{
+	struct device_d *dev = &i2c_priv->adapter.dev;
+	struct stm32_i2c_timings *v, *_v;
+	struct list_head solutions;
+	int ret;
+
+	if (setup->speed >= STM32_I2C_SPEED_END) {
+		dev_err(dev, "speed out of bound {%d/%d}\n",
+		       setup->speed, STM32_I2C_SPEED_END - 1);
+		return -EINVAL;
+	}
+
+	if ((setup->timings.scl_rise_ns > i2c_specs[setup->speed].rise_max) ||
+	    (setup->timings.scl_fall_ns > i2c_specs[setup->speed].fall_max)) {
+		dev_err(dev, "timings out of bound Rise{%d>%d}/Fall{%d>%d}\n",
+		       setup->timings.scl_rise_ns, i2c_specs[setup->speed].rise_max,
+		       setup->timings.scl_fall_ns, i2c_specs[setup->speed].fall_max);
+		return -EINVAL;
+	}
+
+	if (setup->dnf > STM32_I2C_DNF_MAX) {
+		dev_err(dev, "DNF out of bound %d/%d\n",
+		       setup->dnf, STM32_I2C_DNF_MAX);
+		return -EINVAL;
+	}
+
+	if (setup->speed_freq > i2c_specs[setup->speed].rate) {
+		dev_err(dev, "Freq {%d/%d}\n",
+		       setup->speed_freq, i2c_specs[setup->speed].rate);
+		return -EINVAL;
+	}
+
+	INIT_LIST_HEAD(&solutions);
+	ret = stm32_i2c_compute_solutions(setup, &solutions);
+	if (ret) {
+		if (ret == -EPERM)
+			dev_err(dev, "No prescaler solution\n");
+		goto exit;
+	}
+
+	ret = stm32_i2c_choose_solution(setup, &solutions, output);
+	if (ret) {
+		if (ret == -EPERM)
+			dev_err(dev, "no solution at all\n");
+		goto exit;
+	}
+
+	dev_dbg(dev, "Presc: %i, scldel: %i, sdadel: %i, scll: %i, sclh: %i\n",
+		output->presc,
+		output->scldel, output->sdadel,
+		output->scll, output->sclh);
+
+exit:
+	/* Release list and memory */
+	list_for_each_entry_safe(v, _v, &solutions, node) {
+		list_del(&v->node);
+		free(v);
+	}
+
+	return ret;
+}
+
+static int stm32_i2c_setup_timing(struct stm32_i2c *i2c_priv,
+				  enum stm32_i2c_speed speed,
+				  struct stm32_i2c_timings *timing)
+{
+	struct device_d *dev = &i2c_priv->adapter.dev;
+	struct stm32_i2c_setup *setup = &i2c_priv->setup;
+	int ret = 0;
+
+	setup->speed = speed;
+	setup->speed_freq = i2c_specs[setup->speed].rate;
+	setup->clock_src = clk_get_rate(i2c_priv->clk);
+
+	if (!setup->clock_src) {
+		dev_err(dev, "clock rate is 0\n");
+		return -EINVAL;
+	}
+
+	do {
+		ret = stm32_i2c_compute_timing(i2c_priv, setup, timing);
+		if (ret) {
+			dev_dbg(dev, "failed to compute I2C timings.\n");
+			if (speed > STM32_I2C_SPEED_STANDARD) {
+				speed--;
+				setup->speed = speed;
+				setup->speed_freq = i2c_specs[setup->speed].rate;
+				dev_dbg(dev, "downgrade I2C Speed Freq to (%i)\n",
+					i2c_specs[setup->speed].rate);
+			} else {
+				break;
+			}
+		}
+	} while (ret);
+
+	if (ret) {
+		dev_err(dev, "impossible to compute I2C timings.\n");
+		return ret;
+	}
+
+	dev_dbg(dev, "I2C Speed(%i), Freq(%i), Clk Source(%i)\n",
+		setup->speed, setup->speed_freq, setup->clock_src);
+	dev_dbg(dev, "I2C Rise(%i) and Fall(%i) Time\n",
+		 setup->timings.scl_rise_ns, setup->timings.scl_fall_ns);
+	dev_dbg(dev, "I2C Analog Filter(%s), DNF(%i)\n",
+		 setup->analog_filter ? "On" : "Off", setup->dnf);
+
+	return 0;
+}
+
+static int stm32_i2c_hw_config(struct stm32_i2c *i2c_priv,
+			       enum stm32_i2c_speed speed)
+{
+	struct stm32_i2c_regs *regs = i2c_priv->regs;
+	struct stm32_i2c_timings t;
+	int ret;
+	u32 timing = 0;
+
+	ret = stm32_i2c_setup_timing(i2c_priv, speed, &t);
+	if (ret)
+		return ret;
+
+	/* Disable I2C */
+	clrbits_le32(&regs->cr1, STM32_I2C_CR1_PE);
+
+	/* Timing settings */
+	timing |= STM32_I2C_TIMINGR_PRESC(t.presc);
+	timing |= STM32_I2C_TIMINGR_SCLDEL(t.scldel);
+	timing |= STM32_I2C_TIMINGR_SDADEL(t.sdadel);
+	timing |= STM32_I2C_TIMINGR_SCLH(t.sclh);
+	timing |= STM32_I2C_TIMINGR_SCLL(t.scll);
+	writel(timing, &regs->timingr);
+
+	/* Enable I2C */
+	if (i2c_priv->setup.analog_filter)
+		clrbits_le32(&regs->cr1, STM32_I2C_CR1_ANFOFF);
+	else
+		setbits_le32(&regs->cr1, STM32_I2C_CR1_ANFOFF);
+	setbits_le32(&regs->cr1, STM32_I2C_CR1_PE);
+
+	return 0;
+}
+
+static int stm32_i2c_set_bus_speed(struct stm32_i2c *i2c_priv, unsigned speed)
+{
+	struct device_d *parent_dev = i2c_priv->adapter.dev.parent;
+	enum stm32_i2c_speed stm32_speed;
+	switch (speed) {
+	case STANDARD_RATE:
+		stm32_speed = STM32_I2C_SPEED_STANDARD;
+		break;
+	case FAST_RATE:
+		stm32_speed = STM32_I2C_SPEED_FAST;
+		break;
+	case FAST_PLUS_RATE:
+		stm32_speed = STM32_I2C_SPEED_FAST_PLUS;
+		break;
+	default:
+		dev_warn(parent_dev, "Speed %d not supported\n", speed);
+		return -EINVAL;
+	}
+
+	return stm32_i2c_hw_config(i2c_priv, stm32_speed);
+}
+
+static int __init stm32_i2c_probe(struct device_d *dev)
+{
+	struct resource *iores;
+	struct stm32_i2c *stm32_i2c;
+	struct i2c_platform_data *pdata;
+	struct reset_control *rst;
+	const struct stm32_i2c_setup *setup;
+	struct i2c_timings *timings;
+	int ret;
+
+	pdata = dev->platform_data;
+
+	stm32_i2c = xzalloc(sizeof(*stm32_i2c));
+
+	stm32_i2c->clk = clk_get(dev, NULL);
+	if (IS_ERR(stm32_i2c->clk))
+		return PTR_ERR(stm32_i2c->clk);
+	clk_enable(stm32_i2c->clk);
+
+	rst = reset_control_get(dev, NULL);
+	if (IS_ERR(rst))
+		return PTR_ERR(rst);
+
+	reset_control_assert(rst);
+	udelay(2);
+	reset_control_deassert(rst);
+
+	ret = dev_get_drvdata(dev, (const void **)&setup);
+	if (ret)
+		return ret;
+
+	stm32_i2c->setup = *setup;
+	timings = &stm32_i2c->setup.timings;
+
+	/* We've our own defaults, so don't use the i2c_parse_fw_timings ones */
+	i2c_parse_fw_timings(dev, timings, false);
+
+	if (!timings->bus_freq_hz)
+		timings->bus_freq_hz = STANDARD_RATE;
+	if (!timings->scl_rise_ns)
+		timings->scl_rise_ns = STM32_I2C_RISE_TIME_DEFAULT;
+	if (!timings->scl_fall_ns)
+		timings->scl_fall_ns = STM32_I2C_FALL_TIME_DEFAULT;
+
+	/* Setup stm32_i2c driver structure */
+	stm32_i2c->adapter.master_xfer = stm32_i2c_xfer;
+	stm32_i2c->adapter.nr = dev->id;
+	stm32_i2c->adapter.dev.parent = dev;
+	stm32_i2c->adapter.dev.device_node = dev->device_node;
+	iores = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(iores))
+		return PTR_ERR(iores);
+
+	stm32_i2c->regs = IOMEM(iores->start);
+
+	if (pdata && pdata->bitrate)
+		timings->bus_freq_hz = pdata->bitrate;
+
+	ret = stm32_i2c_set_bus_speed(stm32_i2c, timings->bus_freq_hz);
+	if (ret)
+		return ret;
+
+	return i2c_add_numbered_adapter(&stm32_i2c->adapter);
+}
+
+static const struct stm32_i2c_setup stm32f7_setup = {
+	.dnf = STM32_I2C_DNF_DEFAULT,
+	.analog_filter = STM32_I2C_ANALOG_FILTER_ENABLE,
+};
+
+static __maybe_unused struct of_device_id stm32_i2c_dt_ids[] = {
+	{ .compatible = "st,stm32f7-i2c", .data = &stm32f7_setup, },
+	{ /* sentinel */ }
+};
+
+static struct driver_d stm32_i2c_driver = {
+	.probe	= stm32_i2c_probe,
+	.name	= "stm32f7-i2c",
+	.of_compatible = DRV_OF_COMPAT(stm32_i2c_dt_ids),
+};
+coredevice_platform_driver(stm32_i2c_driver);
-- 
2.23.0


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