--- /dev/null
+/*
+ * Renesas RIIC driver
+ *
+ * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
+ * Copyright (C) 2013 Renesas Solutions Corp.
+ *
+ * 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.
+ */
+
+/*
+ * 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>
+
+#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 ICSR2_NACKF 0x10
+
+/* ICBRx (@ PCLK 33MHz) */
+#define ICBR_RESERVED 0xe0 /* Should be 1 on writes */
+#define ICBRL_SP100K (19 | ICBR_RESERVED)
+#define ICBRH_SP100K (16 | ICBR_RESERVED)
+#define ICBRL_SP400K (21 | ICBR_RESERVED)
+#define ICBRH_SP400K (9 | ICBR_RESERVED)
+
+#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, ret;
+ u8 start_bit;
+
+ ret = clk_prepare_enable(riic->clk);
+ if (ret)
+ return ret;
+
+ 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:
+ clk_disable_unprepare(riic->clk);
+
+ 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) {
+ val = !!(riic->msg->flags & I2C_M_RD);
+ if (val)
+ /* 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 |= (riic->msg->addr << 1);
+ } 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->err = -ENXIO;
+ } else if (riic->bytes_left) {
+ return IRQ_NONE;
+ }
+
+ if (riic->is_last || riic->err)
+ writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
+
+ writeb(0, riic->base + 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)
+ writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
+
+ riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
+
+ writeb(0, riic->base + RIIC_ICIER);
+ complete(&riic->msg_done);
+ } 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 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, u32 spd)
+{
+ int ret;
+ unsigned long rate;
+
+ ret = clk_prepare_enable(riic->clk);
+ if (ret)
+ return ret;
+
+ /*
+ * TODO: Implement formula to calculate the timing values depending on
+ * variable parent clock rate and arbitrary bus speed
+ */
+ rate = clk_get_rate(riic->clk);
+ if (rate != 33325000) {
+ dev_err(&riic->adapter.dev,
+ "invalid parent clk (%lu). Must be 33325000Hz\n", rate);
+ clk_disable_unprepare(riic->clk);
+ return -EINVAL;
+ }
+
+ /* 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);
+
+ switch (spd) {
+ case 100000:
+ writeb(ICMR1_CKS(3), riic->base + RIIC_ICMR1);
+ writeb(ICBRH_SP100K, riic->base + RIIC_ICBRH);
+ writeb(ICBRL_SP100K, riic->base + RIIC_ICBRL);
+ break;
+ case 400000:
+ writeb(ICMR1_CKS(1), riic->base + RIIC_ICMR1);
+ writeb(ICBRH_SP400K, riic->base + RIIC_ICBRH);
+ writeb(ICBRL_SP400K, riic->base + RIIC_ICBRL);
+ break;
+ default:
+ dev_err(&riic->adapter.dev,
+ "unsupported bus speed (%dHz). Use 100000 or 400000\n", spd);
+ clk_disable_unprepare(riic->clk);
+ return -EINVAL;
+ }
+
+ 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);
+
+ clk_disable_unprepare(riic->clk);
+
+ return 0;
+}
+
+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 = 5, .isr = riic_tend_isr, .name = "riic-nack" },
+};
+
+static int riic_i2c_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct riic_dev *riic;
+ struct i2c_adapter *adap;
+ struct resource *res;
+ u32 bus_rate = 0;
+ int i, ret;
+
+ riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
+ if (!riic)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ riic->base = devm_ioremap_resource(&pdev->dev, res);
+ 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);
+ }
+
+ for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
+ res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
+ if (!res)
+ return -ENODEV;
+
+ ret = devm_request_irq(&pdev->dev, res->start, 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);
+ strlcpy(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);
+
+ of_property_read_u32(np, "clock-frequency", &bus_rate);
+ ret = riic_init_hw(riic, bus_rate);
+ if (ret)
+ return ret;
+
+
+ ret = i2c_add_adapter(adap);
+ if (ret) {
+ dev_err(&pdev->dev, "failed to add adapter\n");
+ return ret;
+ }
+
+ platform_set_drvdata(pdev, riic);
+
+ dev_info(&pdev->dev, "registered with %dHz bus speed\n", bus_rate);
+ return 0;
+}
+
+static int riic_i2c_remove(struct platform_device *pdev)
+{
+ struct riic_dev *riic = platform_get_drvdata(pdev);
+
+ writeb(0, riic->base + RIIC_ICIER);
+ i2c_del_adapter(&riic->adapter);
+
+ return 0;
+}
+
+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 = 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);
Code Review / kvmfornfv.git / blobdiff