[RFC 3/4] i2c: rcar: add slave support

Wolfram Sang
2014-09-09T14:58:57Z

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
drivers/i2c/busses/i2c-rcar.c | 122 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 113 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 1cc146cfc1f3..fe875d994441 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -48,6 +48,12 @@
#define ICMAR 0x20 /* master address */
#define ICRXTX 0x24 /* data port */

+/* ICSCR */
+#define SDBS (1 << 3) /* slave data buffer select */
+#define SIE (1 << 2) /* slave interface enable */
+#define GCAE (1 << 1) /* general call address enable */
+#define FNA (1 << 0) /* forced non acknowledgement */
+
/* ICMCR */
#define MDBS (1 << 7) /* non-fifo mode switch */
#define FSCL (1 << 6) /* override SCL pin */
@@ -58,6 +64,15 @@
#define FSB (1 << 1) /* force stop bit */
#define ESG (1 << 0) /* en startbit gen */

+/* ICSSR (also for ICSIER) */
+#define GCAR (1 << 6) /* general call received */
+#define STM (1 << 5) /* slave transmit mode */
+#define SSR (1 << 4) /* stop received */
+#define SDE (1 << 3) /* slave data empty */
+#define SDT (1 << 2) /* slave data transmitted */
+#define SDR (1 << 1) /* slave data received */
+#define SAR (1 << 0) /* slave addr received */
+
/* ICMSR (also for ICMIE) */
#define MNR (1 << 6) /* nack received */
#define MAL (1 << 5) /* arbitration lost */
@@ -103,6 +118,7 @@ struct rcar_i2c_priv {
u32 icccr;
u32 flags;
enum rcar_i2c_type devtype;
+ struct i2c_client *slave;
};

#define rcar_i2c_priv_to_dev(p) ((p)->adap.dev.parent)
@@ -126,15 +142,6 @@ static u32 rcar_i2c_read(struct rcar_i2c_priv *priv, int reg)

static void rcar_i2c_init(struct rcar_i2c_priv *priv)
{
- /*
- * reset slave mode.
- * slave mode is not used on this driver
- */
- rcar_i2c_write(priv, ICSIER, 0);
- rcar_i2c_write(priv, ICSAR, 0);
- rcar_i2c_write(priv, ICSCR, 0);
- rcar_i2c_write(priv, ICSSR, 0);
-
/* reset master mode */
rcar_i2c_write(priv, ICMIER, 0);
rcar_i2c_write(priv, ICMCR, 0);
@@ -362,6 +369,63 @@ static int rcar_i2c_irq_recv(struct rcar_i2c_priv *priv, u32 msr)
return 0;
}

+static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
+{
+ u32 ssr_raw, ssr_filtered;
+ u8 value;
+
+ ssr_raw = rcar_i2c_read(priv, ICSSR) & 0xff;
+ ssr_filtered = ssr_raw & rcar_i2c_read(priv, ICSIER);
+
+ if (!ssr_filtered)
+ return false;
+
+ /* address detected */
+ if (ssr_filtered & SAR) {
+ /* read or write request */
+ if (ssr_raw & STM) {
+ i2c_slave_event(priv->slave, I2C_SLAVE_REQ_READ_START, &value);
+ rcar_i2c_write(priv, ICRXTX, value);
+ rcar_i2c_write(priv, ICSIER, SDE | SSR | SAR);
+ } else {
+ i2c_slave_event(priv->slave, I2C_SLAVE_REQ_WRITE_START, NULL);
+ rcar_i2c_read(priv, ICRXTX); /* dummy read */
+ rcar_i2c_write(priv, ICSIER, SDR | SSR | SAR);
+ }
+
+ rcar_i2c_write(priv, ICSSR, ~SAR & 0xff);
+ }
+
+ /* master sent stop */
+ if (ssr_filtered & SSR) {
+ i2c_slave_event(priv->slave, I2C_SLAVE_STOP, NULL);
+ rcar_i2c_write(priv, ICSIER, SAR | SSR);
+ rcar_i2c_write(priv, ICSSR, ~SSR & 0xff);
+ }
+
+ /* master wants to write to us */
+ if (ssr_filtered & SDR) {
+ int ret;
+
+ value = rcar_i2c_read(priv, ICRXTX);
+ ret = i2c_slave_event(priv->slave, I2C_SLAVE_REQ_WRITE_END, &value);
+ /* Send NACK in case of error */
+ rcar_i2c_write(priv, ICSCR, SIE | SDBS | (ret < 0 ? FNA : 0));
+ i2c_slave_event(priv->slave, I2C_SLAVE_REQ_WRITE_START, NULL);
+ rcar_i2c_write(priv, ICSSR, ~SDR & 0xff);
+ }
+
+ /* master wants to read from us */
+ if (ssr_filtered & SDE) {
+ i2c_slave_event(priv->slave, I2C_SLAVE_REQ_READ_END, NULL);
+ i2c_slave_event(priv->slave, I2C_SLAVE_REQ_READ_START, &value);
+ rcar_i2c_write(priv, ICRXTX, value);
+ rcar_i2c_write(priv, ICSSR, ~SDE & 0xff);
+ }
+
+ return true;
+}
+
static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
{
struct rcar_i2c_priv *priv = ptr;
@@ -370,6 +434,9 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
/*-------------- spin lock -----------------*/
spin_lock(&priv->lock);

+ if (rcar_i2c_slave_irq(priv))
+ goto unlock_out;
+
msr = rcar_i2c_read(priv, ICMSR);

/* Only handle interrupts that are currently enabled */
@@ -408,6 +475,7 @@ out:
wake_up(&priv->wait);
}

+unlock_out:
spin_unlock(&priv->lock);
/*-------------- spin unlock -----------------*/

@@ -498,6 +566,40 @@ out:
return ret;
}

+
+static int rcar_reg_slave(struct i2c_client *slave)
+{
+ struct rcar_i2c_priv *priv = i2c_get_adapdata(slave->adapter);
+
+ if (priv->slave)
+ return -EBUSY;
+
+ if (slave->flags & I2C_CLIENT_TEN)
+ return -EAFNOSUPPORT;
+
+ priv->slave = slave;
+ rcar_i2c_write(priv, ICSAR, slave->addr);
+ rcar_i2c_write(priv, ICSSR, 0);
+ rcar_i2c_write(priv, ICSIER, SAR | SSR);
+ rcar_i2c_write(priv, ICSCR, SIE | SDBS);
+
+ return 0;
+}
+
+static int rcar_unreg_slave(struct i2c_client *slave)
+{
+ struct rcar_i2c_priv *priv = i2c_get_adapdata(slave->adapter);
+
+ WARN_ON(!priv->slave);
+
+ rcar_i2c_write(priv, ICSIER, 0);
+ rcar_i2c_write(priv, ICSCR, 0);
+
+ priv->slave = NULL;
+
+ return 0;
+}
+
static u32 rcar_i2c_func(struct i2c_adapter *adap)
{
/* This HW can't do SMBUS_QUICK and NOSTART */
@@ -507,6 +609,8 @@ static u32 rcar_i2c_func(struct i2c_adapter *adap)
static const struct i2c_algorithm rcar_i2c_algo = {
.master_xfer = rcar_i2c_master_xfer,
.functionality = rcar_i2c_func,
+ .reg_slave = rcar_reg_slave,
+ .unreg_slave = rcar_unreg_slave,
};

static const struct of_device_id rcar_i2c_dt_ids[] = {
--
2.0.0