i2c: octeon: Enable High-Level Controller

Use High-Level Controller (HLC) when possible. The HLC can read/write
up to 8 bytes and is completely optional. The most important difference
of the HLC is that it only requires one interrupt for a transfer
(up to 8 bytes) where the low-level read/write requires 2 interrupts
plus one interrupt per transferred byte. Since the interrupts are costly
using the HLC improves the performance. Also, the HLC provides improved
error handling.

Signed-off-by: David Daney <[e-mail]>
Signed-off-by: Jan Glauber <[e-mail]>
[wsa: fixed trivial checkpatch warnings]
Signed-off-by: Wolfram Sang <[e-mail]>

drivers/i2c/busses/i2c-octeon.c

···
 /* Register offsets */
 #define SW_TWSI			0x00
 #define TWSI_INT		0x10
+#define SW_TWSI_EXT		0x18
 
 /* Controller command patterns */
 #define SW_TWSI_V		BIT_ULL(63)	/* Valid bit */
+#define SW_TWSI_EIA		BIT_ULL(61)	/* Extended internal address */
 #define SW_TWSI_R		BIT_ULL(56)	/* Result or read bit */
+#define SW_TWSI_SOVR		BIT_ULL(55)	/* Size override */
+#define SW_TWSI_SIZE_SHIFT	52
+#define SW_TWSI_ADDR_SHIFT	40
+#define SW_TWSI_IA_SHIFT	32		/* Internal address */
 
 /* Controller opcode word (bits 60:57) */
 #define SW_TWSI_OP_SHIFT	57
+#define SW_TWSI_OP_7		(0ULL << SW_TWSI_OP_SHIFT)
+#define SW_TWSI_OP_7_IA		(1ULL << SW_TWSI_OP_SHIFT)
+#define SW_TWSI_OP_10		(2ULL << SW_TWSI_OP_SHIFT)
+#define SW_TWSI_OP_10_IA	(3ULL << SW_TWSI_OP_SHIFT)
 #define SW_TWSI_OP_TWSI_CLK	(4ULL << SW_TWSI_OP_SHIFT)
 #define SW_TWSI_OP_EOP		(6ULL << SW_TWSI_OP_SHIFT) /* Extended opcode */
 
···
 #define SW_TWSI_EOP_TWSI_RST	(SW_TWSI_OP_EOP | 7ULL << SW_TWSI_EOP_SHIFT)
 
 /* Controller command and status bits */
-#define TWSI_CTL_CE		0x80
+#define TWSI_CTL_CE		0x80	/* High level controller enable */
 #define TWSI_CTL_ENAB		0x40	/* Bus enable */
 #define TWSI_CTL_STA		0x20	/* Master-mode start, HW clears when done */
 #define TWSI_CTL_STP		0x10	/* Master-mode stop, HW clears when done */
···
 #define STAT_IDLE		0xF8
 
 /* TWSI_INT values */
+#define TWSI_INT_ST_INT		BIT_ULL(0)
+#define TWSI_INT_TS_INT		BIT_ULL(1)
+#define TWSI_INT_CORE_INT	BIT_ULL(2)
+#define TWSI_INT_ST_EN		BIT_ULL(4)
+#define TWSI_INT_TS_EN		BIT_ULL(5)
 #define TWSI_INT_CORE_EN	BIT_ULL(6)
 #define TWSI_INT_SDA_OVR	BIT_ULL(8)
 #define TWSI_INT_SCL_OVR	BIT_ULL(9)
···
 	int sys_freq;
 	void __iomem *twsi_base;
 	struct device *dev;
+	bool hlc_enabled;
 };
 
 static void octeon_i2c_writeq_flush(u64 val, void __iomem *addr)
···
 {
 	/* clear TS/ST/IFLG events */
 	octeon_i2c_write_int(i2c, 0);
+}
+
+/*
+ * Cleanup low-level state & enable high-level controller.
+ */
+static void octeon_i2c_hlc_enable(struct octeon_i2c *i2c)
+{
+	int try = 0;
+	u64 val;
+
+	if (i2c->hlc_enabled)
+		return;
+	i2c->hlc_enabled = true;
+
+	while (1) {
+		val = octeon_i2c_ctl_read(i2c);
+		if (!(val & (TWSI_CTL_STA | TWSI_CTL_STP)))
+			break;
+
+		/* clear IFLG event */
+		if (val & TWSI_CTL_IFLG)
+			octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);
+
+		if (try++ > 100) {
+			pr_err("%s: giving up\n", __func__);
+			break;
+		}
+
+		/* spin until any start/stop has finished */
+		udelay(10);
+	}
+	octeon_i2c_ctl_write(i2c, TWSI_CTL_CE | TWSI_CTL_AAK | TWSI_CTL_ENAB);
+}
+
+static void octeon_i2c_hlc_disable(struct octeon_i2c *i2c)
+{
+	if (!i2c->hlc_enabled)
+		return;
+
+	i2c->hlc_enabled = false;
+	octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);
 }
 
 /* interrupt service routine */
···
 	}
 }
 
+static bool octeon_i2c_hlc_test_ready(struct octeon_i2c *i2c)
+{
+	u64 val = __raw_readq(i2c->twsi_base + SW_TWSI);
+
+	return (val & SW_TWSI_V) == 0;
+}
+
+static void octeon_i2c_hlc_int_enable(struct octeon_i2c *i2c)
+{
+	octeon_i2c_write_int(i2c, TWSI_INT_ST_EN);
+}
+
+static void octeon_i2c_hlc_int_clear(struct octeon_i2c *i2c)
+{
+	/* clear ST/TS events, listen for neither */
+	octeon_i2c_write_int(i2c, TWSI_INT_ST_INT | TWSI_INT_TS_INT);
+}
+
+/**
+ * octeon_i2c_hlc_wait - wait for an HLC operation to complete
+ * @i2c: The struct octeon_i2c
+ *
+ * Returns 0 on success, otherwise -ETIMEDOUT.
+ */
+static int octeon_i2c_hlc_wait(struct octeon_i2c *i2c)
+{
+	int time_left;
+
+	octeon_i2c_hlc_int_enable(i2c);
+	time_left = wait_event_timeout(i2c->queue,
+				       octeon_i2c_hlc_test_ready(i2c),
+				       i2c->adap.timeout);
+	octeon_i2c_int_disable(i2c);
+	if (!time_left) {
+		octeon_i2c_hlc_int_clear(i2c);
+		return -ETIMEDOUT;
+	}
+	return 0;
+}
+
+/* high-level-controller pure read of up to 8 bytes */
+static int octeon_i2c_hlc_read(struct octeon_i2c *i2c, struct i2c_msg *msgs)
+{
+	int i, j, ret = 0;
+	u64 cmd;
+
+	octeon_i2c_hlc_enable(i2c);
+	octeon_i2c_hlc_int_clear(i2c);
+
+	cmd = SW_TWSI_V | SW_TWSI_R | SW_TWSI_SOVR;
+	/* SIZE */
+	cmd |= (u64)(msgs[0].len - 1) << SW_TWSI_SIZE_SHIFT;
+	/* A */
+	cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;
+
+	if (msgs[0].flags & I2C_M_TEN)
+		cmd |= SW_TWSI_OP_10;
+	else
+		cmd |= SW_TWSI_OP_7;
+
+	octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI);
+	ret = octeon_i2c_hlc_wait(i2c);
+	if (ret)
+		goto err;
+
+	cmd = __raw_readq(i2c->twsi_base + SW_TWSI);
+	if ((cmd & SW_TWSI_R) == 0)
+		return -EAGAIN;
+
+	for (i = 0, j = msgs[0].len - 1; i  < msgs[0].len && i < 4; i++, j--)
+		msgs[0].buf[j] = (cmd >> (8 * i)) & 0xff;
+
+	if (msgs[0].len > 4) {
+		cmd = __raw_readq(i2c->twsi_base + SW_TWSI_EXT);
+		for (i = 0; i  < msgs[0].len - 4 && i < 4; i++, j--)
+			msgs[0].buf[j] = (cmd >> (8 * i)) & 0xff;
+	}
+
+err:
+	return ret;
+}
+
+/* high-level-controller pure write of up to 8 bytes */
+static int octeon_i2c_hlc_write(struct octeon_i2c *i2c, struct i2c_msg *msgs)
+{
+	int i, j, ret = 0;
+	u64 cmd;
+
+	octeon_i2c_hlc_enable(i2c);
+	octeon_i2c_hlc_int_clear(i2c);
+
+	cmd = SW_TWSI_V | SW_TWSI_SOVR;
+	/* SIZE */
+	cmd |= (u64)(msgs[0].len - 1) << SW_TWSI_SIZE_SHIFT;
+	/* A */
+	cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;
+
+	if (msgs[0].flags & I2C_M_TEN)
+		cmd |= SW_TWSI_OP_10;
+	else
+		cmd |= SW_TWSI_OP_7;
+
+	for (i = 0, j = msgs[0].len - 1; i  < msgs[0].len && i < 4; i++, j--)
+		cmd |= (u64)msgs[0].buf[j] << (8 * i);
+
+	if (msgs[0].len > 4) {
+		u64 ext = 0;
+
+		for (i = 0; i < msgs[0].len - 4 && i < 4; i++, j--)
+			ext |= (u64)msgs[0].buf[j] << (8 * i);
+		octeon_i2c_writeq_flush(ext, i2c->twsi_base + SW_TWSI_EXT);
+	}
+
+	octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI);
+	ret = octeon_i2c_hlc_wait(i2c);
+	if (ret)
+		goto err;
+
+	cmd = __raw_readq(i2c->twsi_base + SW_TWSI);
+	if ((cmd & SW_TWSI_R) == 0)
+		return -EAGAIN;
+
+	ret = octeon_i2c_check_status(i2c, false);
+
+err:
+	return ret;
+}
+
+/* high-level-controller composite write+read, msg0=addr, msg1=data */
+static int octeon_i2c_hlc_comp_read(struct octeon_i2c *i2c, struct i2c_msg *msgs)
+{
+	int i, j, ret = 0;
+	u64 cmd;
+
+	octeon_i2c_hlc_enable(i2c);
+
+	cmd = SW_TWSI_V | SW_TWSI_R | SW_TWSI_SOVR;
+	/* SIZE */
+	cmd |= (u64)(msgs[1].len - 1) << SW_TWSI_SIZE_SHIFT;
+	/* A */
+	cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;
+
+	if (msgs[0].flags & I2C_M_TEN)
+		cmd |= SW_TWSI_OP_10_IA;
+	else
+		cmd |= SW_TWSI_OP_7_IA;
+
+	if (msgs[0].len == 2) {
+		u64 ext = 0;
+
+		cmd |= SW_TWSI_EIA;
+		ext = (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
+		cmd |= (u64)msgs[0].buf[1] << SW_TWSI_IA_SHIFT;
+		octeon_i2c_writeq_flush(ext, i2c->twsi_base + SW_TWSI_EXT);
+	} else {
+		cmd |= (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
+	}
+
+	octeon_i2c_hlc_int_clear(i2c);
+	octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI);
+
+	ret = octeon_i2c_hlc_wait(i2c);
+	if (ret)
+		goto err;
+
+	cmd = __raw_readq(i2c->twsi_base + SW_TWSI);
+	if ((cmd & SW_TWSI_R) == 0)
+		return -EAGAIN;
+
+	for (i = 0, j = msgs[1].len - 1; i  < msgs[1].len && i < 4; i++, j--)
+		msgs[1].buf[j] = (cmd >> (8 * i)) & 0xff;
+
+	if (msgs[1].len > 4) {
+		cmd = __raw_readq(i2c->twsi_base + SW_TWSI_EXT);
+		for (i = 0; i  < msgs[1].len - 4 && i < 4; i++, j--)
+			msgs[1].buf[j] = (cmd >> (8 * i)) & 0xff;
+	}
+
+err:
+	return ret;
+}
+
+/* high-level-controller composite write+write, m[0]len<=2, m[1]len<=8 */
+static int octeon_i2c_hlc_comp_write(struct octeon_i2c *i2c, struct i2c_msg *msgs)
+{
+	bool set_ext = false;
+	int i, j, ret = 0;
+	u64 cmd, ext = 0;
+
+	octeon_i2c_hlc_enable(i2c);
+
+	cmd = SW_TWSI_V | SW_TWSI_SOVR;
+	/* SIZE */
+	cmd |= (u64)(msgs[1].len - 1) << SW_TWSI_SIZE_SHIFT;
+	/* A */
+	cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;
+
+	if (msgs[0].flags & I2C_M_TEN)
+		cmd |= SW_TWSI_OP_10_IA;
+	else
+		cmd |= SW_TWSI_OP_7_IA;
+
+	if (msgs[0].len == 2) {
+		cmd |= SW_TWSI_EIA;
+		ext |= (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
+		set_ext = true;
+		cmd |= (u64)msgs[0].buf[1] << SW_TWSI_IA_SHIFT;
+	} else {
+		cmd |= (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
+	}
+
+	for (i = 0, j = msgs[1].len - 1; i  < msgs[1].len && i < 4; i++, j--)
+		cmd |= (u64)msgs[1].buf[j] << (8 * i);
+
+	if (msgs[1].len > 4) {
+		for (i = 0; i < msgs[1].len - 4 && i < 4; i++, j--)
+			ext |= (u64)msgs[1].buf[j] << (8 * i);
+		set_ext = true;
+	}
+	if (set_ext)
+		octeon_i2c_writeq_flush(ext, i2c->twsi_base + SW_TWSI_EXT);
+
+	octeon_i2c_hlc_int_clear(i2c);
+	octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI);
+
+	ret = octeon_i2c_hlc_wait(i2c);
+	if (ret)
+		goto err;
+
+	cmd = __raw_readq(i2c->twsi_base + SW_TWSI);
+	if ((cmd & SW_TWSI_R) == 0)
+		return -EAGAIN;
+
+	ret = octeon_i2c_check_status(i2c, false);
+
+err:
+	return ret;
+}
+
 /* calculate and set clock divisors */
 static void octeon_i2c_set_clock(struct octeon_i2c *i2c)
 {
···
 
 static int octeon_i2c_init_lowlevel(struct octeon_i2c *i2c)
 {
-	u8 status;
+	u8 status = 0;
 	int tries;
-
-	/* disable high level controller, enable bus access */
-	octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);
 
 	/* reset controller */
 	octeon_i2c_reg_write(i2c, SW_TWSI_EOP_TWSI_RST, 0);
 
-	for (tries = 10; tries; tries--) {
+	for (tries = 10; tries && status != STAT_IDLE; tries--) {
 		udelay(1);
 		status = octeon_i2c_stat_read(i2c);
 		if (status == STAT_IDLE)
-			return 0;
+			break;
 	}
-	dev_err(i2c->dev, "%s: TWSI_RST failed! (0x%x)\n", __func__, status);
-	return -EIO;
+
+	if (status != STAT_IDLE) {
+		dev_err(i2c->dev, "%s: TWSI_RST failed! (0x%x)\n",
+			__func__, status);
+		return -EIO;
+	}
+
+	/* toggle twice to force both teardowns */
+	octeon_i2c_hlc_enable(i2c);
+	octeon_i2c_hlc_disable(i2c);
+	return 0;
 }
 
 static int octeon_i2c_recovery(struct octeon_i2c *i2c)
···
 {
 	int ret;
 	u8 stat;
+
+	octeon_i2c_hlc_disable(i2c);
 
 	octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB | TWSI_CTL_STA);
 	ret = octeon_i2c_wait(i2c);
···
 	struct octeon_i2c *i2c = i2c_get_adapdata(adap);
 	int i, ret = 0;
 
+	if (num == 1) {
+		if (msgs[0].len > 0 && msgs[0].len <= 8) {
+			if (msgs[0].flags & I2C_M_RD)
+				ret = octeon_i2c_hlc_read(i2c, msgs);
+			else
+				ret = octeon_i2c_hlc_write(i2c, msgs);
+			goto out;
+		}
+	} else if (num == 2) {
+		if ((msgs[0].flags & I2C_M_RD) == 0 &&
+		    (msgs[1].flags & I2C_M_RECV_LEN) == 0 &&
+		    msgs[0].len > 0 && msgs[0].len <= 2 &&
+		    msgs[1].len > 0 && msgs[1].len <= 8 &&
+		    msgs[0].addr == msgs[1].addr) {
+			if (msgs[1].flags & I2C_M_RD)
+				ret = octeon_i2c_hlc_comp_read(i2c, msgs);
+			else
+				ret = octeon_i2c_hlc_comp_write(i2c, msgs);
+			goto out;
+		}
+	}
+
 	for (i = 0; ret == 0 && i < num; i++) {
 		struct i2c_msg *pmsg = &msgs[i];
 
···
 					       pmsg->len);
 	}
 	octeon_i2c_stop(i2c);
-
+out:
 	return (ret != 0) ? ret : num;
 }
 
···
 	 */
 	octeon_i2c_stop(i2c);
 
+	octeon_i2c_hlc_disable(i2c);
 	octeon_i2c_write_int(i2c, 0);
 }