i2c: rcar: add slave support

The first I2C slave provider using the new generic interface.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 115 insertions, 9 deletions

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index d826e82dd997..835057741aa6 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 acknowledgment */
+
 /* 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);
@@ -360,6 +367,63 @@ 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, &value);
+                        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, &value);
+                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, &value);
+                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, &value);
+                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;
@@ -369,6 +433,9 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
         /*-------------- spin lock -----------------*/
         spin_lock(&priv->lock);
 
+        if (rcar_i2c_slave_irq(priv))
+                goto exit;
+
         msr = rcar_i2c_read(priv, ICMSR);
 
         /* Only handle interrupts that are currently enabled */
@@ -499,6 +566,43 @@ 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;
+
+        pm_runtime_forbid(rcar_i2c_priv_to_dev(priv));
+
+        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;
+
+        pm_runtime_allow(rcar_i2c_priv_to_dev(priv));
+
+        return 0;
+}
+
 static u32 rcar_i2c_func(struct i2c_adapter *adap)
 {
         /* This HW can't do SMBUS_QUICK and NOSTART */
@@ -508,6 +612,8 @@ 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[] = {