1 files changed, 509 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-riic.c b/drivers/i2c/busses/i2c-riic.c
new file mode 100644
index 000000000..f0ee8871d
--- /dev/null
+++ b/drivers/i2c/busses/i2c-riic.c
@@ -0,0 +1,509 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Renesas RIIC driver
+ *
+ * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
+ * Copyright (C) 2013 Renesas Solutions Corp.
+ */
+
+/*
+ * This i2c core has a lot of interrupts, namely 8. We use their chaining as
+ * some kind of state machine.
+ *
+ * 1) The main xfer routine kicks off a transmission by putting the start bit
+ * (or repeated start) on the bus and enabling the transmit interrupt (TIE)
+ * since we need to send the slave address + RW bit in every case.
+ *
+ * 2) TIE sends slave address + RW bit and selects how to continue.
+ *
+ * 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
+ * are done, we switch over to the transmission done interrupt (TEIE) and mark
+ * the message as completed (includes sending STOP) there.
+ *
+ * 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
+ * needed to start clocking, then we keep receiving until we are done. Note
+ * that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
+ * writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
+ * message to create the final NACK as sketched in the datasheet. This caused
+ * some subtle races (when byte n was processed and byte n+1 was already
+ * waiting), though, and I started with the safe approach.
+ *
+ * 4) If we got a NACK somewhere, we flag the error and stop the transmission
+ * via NAKIE.
+ *
+ * Also check the comments in the interrupt routines for some gory details.
+ */
+
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/reset.h>
+
+#define RIIC_ICCR1	0x00
+#define RIIC_ICCR2	0x04
+#define RIIC_ICMR1	0x08
+#define RIIC_ICMR3	0x10
+#define RIIC_ICSER	0x18
+#define RIIC_ICIER	0x1c
+#define RIIC_ICSR2	0x24
+#define RIIC_ICBRL	0x34
+#define RIIC_ICBRH	0x38
+#define RIIC_ICDRT	0x3c
+#define RIIC_ICDRR	0x40
+
+#define ICCR1_ICE	0x80
+#define ICCR1_IICRST	0x40
+#define ICCR1_SOWP	0x10
+
+#define ICCR2_BBSY	0x80
+#define ICCR2_SP	0x08
+#define ICCR2_RS	0x04
+#define ICCR2_ST	0x02
+
+#define ICMR1_CKS_MASK	0x70
+#define ICMR1_BCWP	0x08
+#define ICMR1_CKS(_x)	((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)
+
+#define ICMR3_RDRFS	0x20
+#define ICMR3_ACKWP	0x10
+#define ICMR3_ACKBT	0x08
+
+#define ICIER_TIE	0x80
+#define ICIER_TEIE	0x40
+#define ICIER_RIE	0x20
+#define ICIER_NAKIE	0x10
+#define ICIER_SPIE	0x08
+
+#define ICSR2_NACKF	0x10
+
+#define ICBR_RESERVED	0xe0 /* Should be 1 on writes */
+
+#define RIIC_INIT_MSG	-1
+
+struct riic_dev {
+	void __iomem *base;
+	u8 *buf;
+	struct i2c_msg *msg;
+	int bytes_left;
+	int err;
+	int is_last;
+	struct completion msg_done;
+	struct i2c_adapter adapter;
+	struct clk *clk;
+};
+
+struct riic_irq_desc {
+	int res_num;
+	irq_handler_t isr;
+	char *name;
+};
+
+static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
+{
+	writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
+}
+
+static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
+{
+	struct riic_dev *riic = i2c_get_adapdata(adap);
+	unsigned long time_left;
+	int i;
+	u8 start_bit;
+
+	pm_runtime_get_sync(adap->dev.parent);
+
+	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
+		riic->err = -EBUSY;
+		goto out;
+	}
+
+	reinit_completion(&riic->msg_done);
+	riic->err = 0;
+
+	writeb(0, riic->base + RIIC_ICSR2);
+
+	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
+		riic->bytes_left = RIIC_INIT_MSG;
+		riic->buf = msgs[i].buf;
+		riic->msg = &msgs[i];
+		riic->is_last = (i == num - 1);
+
+		writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);
+
+		writeb(start_bit, riic->base + RIIC_ICCR2);
+
+		time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
+		if (time_left == 0)
+			riic->err = -ETIMEDOUT;
+
+		if (riic->err)
+			break;
+
+		start_bit = ICCR2_RS;
+	}
+
+ out:
+	pm_runtime_put(adap->dev.parent);
+
+	return riic->err ?: num;
+}
+
+static irqreturn_t riic_tdre_isr(int irq, void *data)
+{
+	struct riic_dev *riic = data;
+	u8 val;
+
+	if (!riic->bytes_left)
+		return IRQ_NONE;
+
+	if (riic->bytes_left == RIIC_INIT_MSG) {
+		if (riic->msg->flags & I2C_M_RD)
+			/* On read, switch over to receive interrupt */
+			riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
+		else
+			/* On write, initialize length */
+			riic->bytes_left = riic->msg->len;
+
+		val = i2c_8bit_addr_from_msg(riic->msg);
+	} else {
+		val = *riic->buf;
+		riic->buf++;
+		riic->bytes_left--;
+	}
+
+	/*
+	 * Switch to transmission ended interrupt when done. Do check here
+	 * after bytes_left was initialized to support SMBUS_QUICK (new msg has
+	 * 0 length then)
+	 */
+	if (riic->bytes_left == 0)
+		riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);
+
+	/*
+	 * This acks the TIE interrupt. We get another TIE immediately if our
+	 * value could be moved to the shadow shift register right away. So
+	 * this must be after updates to ICIER (where we want to disable TIE)!
+	 */
+	writeb(val, riic->base + RIIC_ICDRT);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t riic_tend_isr(int irq, void *data)
+{
+	struct riic_dev *riic = data;
+
+	if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
+		/* We got a NACKIE */
+		readb(riic->base + RIIC_ICDRR);	/* dummy read */
+		riic_clear_set_bit(riic, ICSR2_NACKF, 0, RIIC_ICSR2);
+		riic->err = -ENXIO;
+	} else if (riic->bytes_left) {
+		return IRQ_NONE;
+	}
+
+	if (riic->is_last || riic->err) {
+		riic_clear_set_bit(riic, ICIER_TEIE, ICIER_SPIE, RIIC_ICIER);
+		writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
+	} else {
+		/* Transfer is complete, but do not send STOP */
+		riic_clear_set_bit(riic, ICIER_TEIE, 0, RIIC_ICIER);
+		complete(&riic->msg_done);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t riic_rdrf_isr(int irq, void *data)
+{
+	struct riic_dev *riic = data;
+
+	if (!riic->bytes_left)
+		return IRQ_NONE;
+
+	if (riic->bytes_left == RIIC_INIT_MSG) {
+		riic->bytes_left = riic->msg->len;
+		readb(riic->base + RIIC_ICDRR);	/* dummy read */
+		return IRQ_HANDLED;
+	}
+
+	if (riic->bytes_left == 1) {
+		/* STOP must come before we set ACKBT! */
+		if (riic->is_last) {
+			riic_clear_set_bit(riic, 0, ICIER_SPIE, RIIC_ICIER);
+			writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
+		}
+
+		riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
+
+	} else {
+		riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
+	}
+
+	/* Reading acks the RIE interrupt */
+	*riic->buf = readb(riic->base + RIIC_ICDRR);
+	riic->buf++;
+	riic->bytes_left--;
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t riic_stop_isr(int irq, void *data)
+{
+	struct riic_dev *riic = data;
+
+	/* read back registers to confirm writes have fully propagated */
+	writeb(0, riic->base + RIIC_ICSR2);
+	readb(riic->base + RIIC_ICSR2);
+	writeb(0, riic->base + RIIC_ICIER);
+	readb(riic->base + RIIC_ICIER);
+
+	complete(&riic->msg_done);
+
+	return IRQ_HANDLED;
+}
+
+static u32 riic_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm riic_algo = {
+	.master_xfer	= riic_xfer,
+	.functionality	= riic_func,
+};
+
+static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
+{
+	int ret = 0;
+	unsigned long rate;
+	int total_ticks, cks, brl, brh;
+
+	pm_runtime_get_sync(riic->adapter.dev.parent);
+
+	if (t->bus_freq_hz > I2C_MAX_FAST_MODE_FREQ) {
+		dev_err(&riic->adapter.dev,
+			"unsupported bus speed (%dHz). %d max\n",
+			t->bus_freq_hz, I2C_MAX_FAST_MODE_FREQ);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	rate = clk_get_rate(riic->clk);
+
+	/*
+	 * Assume the default register settings:
+	 *  FER.SCLE = 1 (SCL sync circuit enabled, adds 2 or 3 cycles)
+	 *  FER.NFE = 1 (noise circuit enabled)
+	 *  MR3.NF = 0 (1 cycle of noise filtered out)
+	 *
+	 * Freq (CKS=000) = (I2CCLK + tr + tf)/ (BRH + 3 + 1) + (BRL + 3 + 1)
+	 * Freq (CKS!=000) = (I2CCLK + tr + tf)/ (BRH + 2 + 1) + (BRL + 2 + 1)
+	 */
+
+	/*
+	 * Determine reference clock rate. We must be able to get the desired
+	 * frequency with only 62 clock ticks max (31 high, 31 low).
+	 * Aim for a duty of 60% LOW, 40% HIGH.
+	 */
+	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz);
+
+	for (cks = 0; cks < 7; cks++) {
+		/*
+		 * 60% low time must be less than BRL + 2 + 1
+		 * BRL max register value is 0x1F.
+		 */
+		brl = ((total_ticks * 6) / 10);
+		if (brl <= (0x1F + 3))
+			break;
+
+		total_ticks /= 2;
+		rate /= 2;
+	}
+
+	if (brl > (0x1F + 3)) {
+		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
+			(unsigned long)t->bus_freq_hz);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	brh = total_ticks - brl;
+
+	/* Remove automatic clock ticks for sync circuit and NF */
+	if (cks == 0) {
+		brl -= 4;
+		brh -= 4;
+	} else {
+		brl -= 3;
+		brh -= 3;
+	}
+
+	/*
+	 * Remove clock ticks for rise and fall times. Convert ns to clock
+	 * ticks.
+	 */
+	brl -= t->scl_fall_ns / (1000000000 / rate);
+	brh -= t->scl_rise_ns / (1000000000 / rate);
+
+	/* Adjust for min register values for when SCLE=1 and NFE=1 */
+	if (brl < 1)
+		brl = 1;
+	if (brh < 1)
+		brh = 1;
+
+	pr_debug("i2c-riic: freq=%lu, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
+		 rate / total_ticks, ((brl + 3) * 100) / (brl + brh + 6),
+		 t->scl_fall_ns / (1000000000 / rate),
+		 t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);
+
+	/* Changing the order of accessing IICRST and ICE may break things! */
+	writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
+	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);
+
+	writeb(ICMR1_CKS(cks), riic->base + RIIC_ICMR1);
+	writeb(brh | ICBR_RESERVED, riic->base + RIIC_ICBRH);
+	writeb(brl | ICBR_RESERVED, riic->base + RIIC_ICBRL);
+
+	writeb(0, riic->base + RIIC_ICSER);
+	writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);
+
+	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
+
+out:
+	pm_runtime_put(riic->adapter.dev.parent);
+	return ret;
+}
+
+static struct riic_irq_desc riic_irqs[] = {
+	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
+	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
+	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
+	{ .res_num = 3, .isr = riic_stop_isr, .name = "riic-stop" },
+	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
+};
+
+static void riic_reset_control_assert(void *data)
+{
+	reset_control_assert(data);
+}
+
+static int riic_i2c_probe(struct platform_device *pdev)
+{
+	struct riic_dev *riic;
+	struct i2c_adapter *adap;
+	struct i2c_timings i2c_t;
+	struct reset_control *rstc;
+	int i, ret;
+
+	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
+	if (!riic)
+		return -ENOMEM;
+
+	riic->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(riic->base))
+		return PTR_ERR(riic->base);
+
+	riic->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(riic->clk)) {
+		dev_err(&pdev->dev, "missing controller clock");
+		return PTR_ERR(riic->clk);
+	}
+
+	rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(rstc))
+		return dev_err_probe(&pdev->dev, PTR_ERR(rstc),
+				     "Error: missing reset ctrl\n");
+
+	ret = reset_control_deassert(rstc);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(&pdev->dev, riic_reset_control_assert, rstc);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
+		ret = platform_get_irq(pdev, riic_irqs[i].res_num);
+		if (ret < 0)
+			return ret;
+
+		ret = devm_request_irq(&pdev->dev, ret, riic_irqs[i].isr,
+				       0, riic_irqs[i].name, riic);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
+			return ret;
+		}
+	}
+
+	adap = &riic->adapter;
+	i2c_set_adapdata(adap, riic);
+	strscpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
+	adap->owner = THIS_MODULE;
+	adap->algo = &riic_algo;
+	adap->dev.parent = &pdev->dev;
+	adap->dev.of_node = pdev->dev.of_node;
+
+	init_completion(&riic->msg_done);
+
+	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);
+
+	pm_runtime_enable(&pdev->dev);
+
+	ret = riic_init_hw(riic, &i2c_t);
+	if (ret)
+		goto out;
+
+	ret = i2c_add_adapter(adap);
+	if (ret)
+		goto out;
+
+	platform_set_drvdata(pdev, riic);
+
+	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
+		 i2c_t.bus_freq_hz);
+	return 0;
+
+out:
+	pm_runtime_disable(&pdev->dev);
+	return ret;
+}
+
+static void riic_i2c_remove(struct platform_device *pdev)
+{
+	struct riic_dev *riic = platform_get_drvdata(pdev);
+
+	pm_runtime_get_sync(&pdev->dev);
+	writeb(0, riic->base + RIIC_ICIER);
+	pm_runtime_put(&pdev->dev);
+	i2c_del_adapter(&riic->adapter);
+	pm_runtime_disable(&pdev->dev);
+}
+
+static const struct of_device_id riic_i2c_dt_ids[] = {
+	{ .compatible = "renesas,riic-rz", },
+	{ /* Sentinel */ },
+};
+
+static struct platform_driver riic_i2c_driver = {
+	.probe		= riic_i2c_probe,
+	.remove_new	= riic_i2c_remove,
+	.driver		= {
+		.name	= "i2c-riic",
+		.of_match_table = riic_i2c_dt_ids,
+	},
+};
+
+module_platform_driver(riic_i2c_driver);
+
+MODULE_DESCRIPTION("Renesas RIIC adapter");
+MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);