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+/*
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+ * Renesas RIIC driver
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+ *
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+ * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
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+ * Copyright (C) 2013 Renesas Solutions Corp.
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+ *
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+ * This program is free software; you can redistribute it and/or modify it
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+ * under the terms of the GNU General Public License version 2 as published by
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+ * the Free Software Foundation.
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+ */
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+
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+/*
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+ * This i2c core has a lot of interrupts, namely 8. We use their chaining as
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+ * some kind of state machine.
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+ *
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+ * 1) The main xfer routine kicks off a transmission by putting the start bit
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+ * (or repeated start) on the bus and enabling the transmit interrupt (TIE)
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+ * since we need to send the slave address + RW bit in every case.
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+ *
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+ * 2) TIE sends slave address + RW bit and selects how to continue.
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+ *
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+ * 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
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+ * are done, we switch over to the transmission done interrupt (TEIE) and mark
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+ * the message as completed (includes sending STOP) there.
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+ *
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+ * 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
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+ * needed to start clocking, then we keep receiving until we are done. Note
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+ * that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
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+ * writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
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+ * message to create the final NACK as sketched in the datasheet. This caused
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+ * some subtle races (when byte n was processed and byte n+1 was already
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+ * waiting), though, and I started with the safe approach.
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+ *
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+ * 4) If we got a NACK somewhere, we flag the error and stop the transmission
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+ * via NAKIE.
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+ *
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+ * Also check the comments in the interrupt routines for some gory details.
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+ */
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+
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+#include <linux/clk.h>
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+#include <linux/completion.h>
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+#include <linux/err.h>
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+#include <linux/i2c.h>
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+#include <linux/interrupt.h>
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+#include <linux/io.h>
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+#include <linux/module.h>
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+#include <linux/of.h>
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+#include <linux/platform_device.h>
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+
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+#define RIIC_ICCR1 0x00
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+#define RIIC_ICCR2 0x04
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+#define RIIC_ICMR1 0x08
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+#define RIIC_ICMR3 0x10
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+#define RIIC_ICSER 0x18
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+#define RIIC_ICIER 0x1c
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+#define RIIC_ICSR2 0x24
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+#define RIIC_ICBRL 0x34
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+#define RIIC_ICBRH 0x38
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+#define RIIC_ICDRT 0x3c
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+#define RIIC_ICDRR 0x40
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+
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+#define ICCR1_ICE 0x80
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+#define ICCR1_IICRST 0x40
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+#define ICCR1_SOWP 0x10
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+
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+#define ICCR2_BBSY 0x80
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+#define ICCR2_SP 0x08
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+#define ICCR2_RS 0x04
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+#define ICCR2_ST 0x02
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+
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+#define ICMR1_CKS_MASK 0x70
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+#define ICMR1_BCWP 0x08
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+#define ICMR1_CKS(_x) ((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)
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+
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+#define ICMR3_RDRFS 0x20
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+#define ICMR3_ACKWP 0x10
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+#define ICMR3_ACKBT 0x08
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+
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+#define ICIER_TIE 0x80
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+#define ICIER_TEIE 0x40
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+#define ICIER_RIE 0x20
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+#define ICIER_NAKIE 0x10
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+
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+#define ICSR2_NACKF 0x10
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+
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+/* ICBRx (@ PCLK 33MHz) */
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+#define ICBR_RESERVED 0xe0 /* Should be 1 on writes */
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+#define ICBRL_SP100K (19 | ICBR_RESERVED)
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+#define ICBRH_SP100K (16 | ICBR_RESERVED)
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+#define ICBRL_SP400K (21 | ICBR_RESERVED)
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+#define ICBRH_SP400K (9 | ICBR_RESERVED)
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+
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+#define RIIC_INIT_MSG -1
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+
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+struct riic_dev {
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+ void __iomem *base;
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+ u8 *buf;
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+ struct i2c_msg *msg;
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+ int bytes_left;
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+ int err;
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+ int is_last;
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+ struct completion msg_done;
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+ struct i2c_adapter adapter;
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+ struct clk *clk;
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+};
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+
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+struct riic_irq_desc {
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+ int res_num;
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+ irq_handler_t isr;
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+ char *name;
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+};
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+
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+static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
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+{
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+ writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
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+}
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+
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+static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
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+{
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+ struct riic_dev *riic = i2c_get_adapdata(adap);
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+ unsigned long time_left;
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+ int i, ret;
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+ u8 start_bit;
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+
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+ ret = clk_prepare_enable(riic->clk);
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+ if (ret)
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+ return ret;
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+
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+ if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
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+ riic->err = -EBUSY;
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+ goto out;
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+ }
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+
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+ reinit_completion(&riic->msg_done);
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+ riic->err = 0;
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+
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+ writeb(0, riic->base + RIIC_ICSR2);
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+
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+ for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
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+ riic->bytes_left = RIIC_INIT_MSG;
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+ riic->buf = msgs[i].buf;
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+ riic->msg = &msgs[i];
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+ riic->is_last = (i == num - 1);
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+
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+ writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);
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+
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+ writeb(start_bit, riic->base + RIIC_ICCR2);
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+
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+ time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
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+ if (time_left == 0)
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+ riic->err = -ETIMEDOUT;
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+
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+ if (riic->err)
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+ break;
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+
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+ start_bit = ICCR2_RS;
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+ }
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+
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+ out:
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+ clk_disable_unprepare(riic->clk);
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+
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+ return riic->err ?: num;
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+}
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+
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+static irqreturn_t riic_tdre_isr(int irq, void *data)
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+{
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+ struct riic_dev *riic = data;
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+ u8 val;
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+
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+ if (!riic->bytes_left)
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+ return IRQ_NONE;
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+
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+ if (riic->bytes_left == RIIC_INIT_MSG) {
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+ val = !!(riic->msg->flags & I2C_M_RD);
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+ if (val)
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+ /* On read, switch over to receive interrupt */
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+ riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
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+ else
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+ /* On write, initialize length */
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+ riic->bytes_left = riic->msg->len;
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+
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+ val |= (riic->msg->addr << 1);
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+ } else {
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+ val = *riic->buf;
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+ riic->buf++;
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+ riic->bytes_left--;
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+ }
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+
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+ /*
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+ * Switch to transmission ended interrupt when done. Do check here
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+ * after bytes_left was initialized to support SMBUS_QUICK (new msg has
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+ * 0 length then)
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+ */
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+ if (riic->bytes_left == 0)
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+ riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);
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+
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+ /*
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+ * This acks the TIE interrupt. We get another TIE immediately if our
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+ * value could be moved to the shadow shift register right away. So
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+ * this must be after updates to ICIER (where we want to disable TIE)!
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+ */
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+ writeb(val, riic->base + RIIC_ICDRT);
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+
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+ return IRQ_HANDLED;
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+}
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+
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+static irqreturn_t riic_tend_isr(int irq, void *data)
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+{
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+ struct riic_dev *riic = data;
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+
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+ if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
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+ /* We got a NACKIE */
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+ readb(riic->base + RIIC_ICDRR); /* dummy read */
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+ riic->err = -ENXIO;
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+ } else if (riic->bytes_left) {
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+ return IRQ_NONE;
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+ }
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+
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+ if (riic->is_last || riic->err)
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+ writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
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+
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+ writeb(0, riic->base + RIIC_ICIER);
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+ complete(&riic->msg_done);
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+
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+ return IRQ_HANDLED;
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+}
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+
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+static irqreturn_t riic_rdrf_isr(int irq, void *data)
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+{
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+ struct riic_dev *riic = data;
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+
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+ if (!riic->bytes_left)
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+ return IRQ_NONE;
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+
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+ if (riic->bytes_left == RIIC_INIT_MSG) {
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+ riic->bytes_left = riic->msg->len;
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+ readb(riic->base + RIIC_ICDRR); /* dummy read */
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+ return IRQ_HANDLED;
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+ }
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+
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+ if (riic->bytes_left == 1) {
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+ /* STOP must come before we set ACKBT! */
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+ if (riic->is_last)
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+ writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
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+
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+ riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
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+
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+ writeb(0, riic->base + RIIC_ICIER);
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+ complete(&riic->msg_done);
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+ } else {
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+ riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
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+ }
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+
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+ /* Reading acks the RIE interrupt */
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+ *riic->buf = readb(riic->base + RIIC_ICDRR);
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+ riic->buf++;
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+ riic->bytes_left--;
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+
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+ return IRQ_HANDLED;
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+}
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+
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+static u32 riic_func(struct i2c_adapter *adap)
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+{
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+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
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+}
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+
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+static const struct i2c_algorithm riic_algo = {
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+ .master_xfer = riic_xfer,
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+ .functionality = riic_func,
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+};
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+
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+static int riic_init_hw(struct riic_dev *riic, u32 spd)
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+{
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+ int ret;
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+ unsigned long rate;
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+
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+ ret = clk_prepare_enable(riic->clk);
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+ if (ret)
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+ return ret;
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+
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+ /*
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+ * TODO: Implement formula to calculate the timing values depending on
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+ * variable parent clock rate and arbitrary bus speed
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+ */
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+ rate = clk_get_rate(riic->clk);
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+ if (rate != 33325000) {
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+ dev_err(&riic->adapter.dev,
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+ "invalid parent clk (%lu). Must be 33325000Hz\n", rate);
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+ clk_disable_unprepare(riic->clk);
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+ return -EINVAL;
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+ }
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+
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+ /* Changing the order of accessing IICRST and ICE may break things! */
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+ writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
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+ riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);
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+
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+ switch (spd) {
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+ case 100000:
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+ writeb(ICMR1_CKS(3), riic->base + RIIC_ICMR1);
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+ writeb(ICBRH_SP100K, riic->base + RIIC_ICBRH);
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+ writeb(ICBRL_SP100K, riic->base + RIIC_ICBRL);
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+ break;
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+ case 400000:
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+ writeb(ICMR1_CKS(1), riic->base + RIIC_ICMR1);
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+ writeb(ICBRH_SP400K, riic->base + RIIC_ICBRH);
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+ writeb(ICBRL_SP400K, riic->base + RIIC_ICBRL);
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+ break;
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+ default:
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+ dev_err(&riic->adapter.dev,
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+ "unsupported bus speed (%dHz). Use 100000 or 400000\n", spd);
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+ clk_disable_unprepare(riic->clk);
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+ return -EINVAL;
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+ }
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+
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+ writeb(0, riic->base + RIIC_ICSER);
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+ writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);
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+
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+ riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
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+
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+ clk_disable_unprepare(riic->clk);
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+
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+ return 0;
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+}
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+
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+static struct riic_irq_desc riic_irqs[] = {
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+ { .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
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+ { .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
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+ { .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
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+ { .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
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+};
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+
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+static int riic_i2c_probe(struct platform_device *pdev)
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+{
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+ struct device_node *np = pdev->dev.of_node;
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+ struct riic_dev *riic;
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+ struct i2c_adapter *adap;
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+ struct resource *res;
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+ u32 bus_rate = 0;
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+ int i, ret;
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+
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+ riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
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+ if (!riic)
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+ return -ENOMEM;
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+
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+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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+ riic->base = devm_ioremap_resource(&pdev->dev, res);
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+ if (IS_ERR(riic->base))
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+ return PTR_ERR(riic->base);
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+
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+ riic->clk = devm_clk_get(&pdev->dev, NULL);
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+ if (IS_ERR(riic->clk)) {
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+ dev_err(&pdev->dev, "missing controller clock");
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+ return PTR_ERR(riic->clk);
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+ }
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+
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+ for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
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+ res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
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+ if (!res)
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+ return -ENODEV;
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+
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+ ret = devm_request_irq(&pdev->dev, res->start, riic_irqs[i].isr,
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+ 0, riic_irqs[i].name, riic);
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+ if (ret) {
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+ dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
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+ return ret;
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+ }
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+ }
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+
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+ adap = &riic->adapter;
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+ i2c_set_adapdata(adap, riic);
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+ strlcpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
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+ adap->owner = THIS_MODULE;
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+ adap->algo = &riic_algo;
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+ adap->dev.parent = &pdev->dev;
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+ adap->dev.of_node = pdev->dev.of_node;
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+
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+ init_completion(&riic->msg_done);
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+
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+ of_property_read_u32(np, "clock-frequency", &bus_rate);
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+ ret = riic_init_hw(riic, bus_rate);
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+ if (ret)
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+ 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 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",
|
|
|
+ .owner = THIS_MODULE,
|
|
|
+ .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);
|