[PATCH v1 1/2] i2c: microchip: fix ack sending logic

[Conor Dooley <conor.dooley@microchip.com>]

"Master receive mode" was not correctly sending ACKs/NACKs in the
interrupt handler. Bring the handling of M_SLAR_ACK, M_RX_DATA_ACKED &
M_RX_DATA_NACKED in line with the Linux driver.

Fixes: 0dc0d1e094 ("i2c: Add Microchip PolarFire SoC I2C driver")
Reported-by: Shravan Chippa <shravan.chippa@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 drivers/i2c/i2c-microchip.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/i2c-microchip.c b/drivers/i2c/i2c-microchip.c
index 12f65d0af7..3a27459386 100644
--- a/drivers/i2c/i2c-microchip.c
+++ b/drivers/i2c/i2c-microchip.c
@@ -2,8 +2,9 @@
 /*
  * Microchip I2C controller driver
  *
- * Copyright (C) 2021 Microchip Technology Inc.
+ * Copyright (C) 2021-2022 Microchip Technology Inc.
  * Padmarao Begari <padmarao.begari@microchip.com>
+ * Conor Dooley <conor.dooley@microchip.com>
  */
 #include <common.h>
 #include <clk.h>
@@ -265,16 +266,27 @@ static int mpfs_i2c_service_handler(struct mpfs_i2c_bus *bus)
 		}
 		break;
 	case STATUS_M_SLAR_ACK:
-		ctrl = readl(bus->base + MPFS_I2C_CTRL);
-		ctrl |= CTRL_AA;
-		writel(ctrl, bus->base + MPFS_I2C_CTRL);
-		if (bus->msg_len == 0) {
+		if (bus->msg_len > 1u) {
+			ctrl = readl(bus->base + MPFS_I2C_CTRL);
+			ctrl |= CTRL_AA;
+			writel(ctrl, bus->base + MPFS_I2C_CTRL);
+		} else if (bus->msg_len == 1u) {
+			ctrl = readl(bus->base + MPFS_I2C_CTRL);
+			ctrl &= ~CTRL_AA;
+			writel(ctrl, bus->base + MPFS_I2C_CTRL);
+		} else {
+			ctrl = readl(bus->base + MPFS_I2C_CTRL);
+			ctrl |= CTRL_AA;
+			writel(ctrl, bus->base + MPFS_I2C_CTRL);
 			/* On the last byte to be transmitted, send STOP */
 			mpfs_i2c_stop(bus);
 			finish = true;
 		}
 		break;
 	case STATUS_M_RX_DATA_ACKED:
+		mpfs_i2c_empty_rx(bus);
+		break;
+	case STATUS_M_RX_DATA_NACKED:
 		mpfs_i2c_empty_rx(bus);
 		if (bus->msg_len == 0) {
 			/* On the last byte to be transmitted, send STOP */
@@ -283,7 +295,6 @@ static int mpfs_i2c_service_handler(struct mpfs_i2c_bus *bus)
 		}
 		break;
 	case STATUS_M_TX_DATA_NACK:
-	case STATUS_M_RX_DATA_NACKED:
 	case STATUS_M_SLAR_NACK:
 	case STATUS_M_SLAW_NACK:
 		bus->msg_err = -ENXIO;
-- 
2.38.0