[PATCH v5 2/6] i2c: npcm: use a software flag to indicate a BER condition

[Tyrone Ting <warp5tw@gmail.com>]

From: Tyrone Ting <kfting@nuvoton.com>

If not clearing the BB (bus busy) condition in the BER (bus error)
interrupt, the driver causes a timeout and hence the i2c core
doesn't do the i2c transfer retry but returns the driver's return
value to the upper layer instead.

Clear the BB condition in the BER interrupt and a software flag is
used. The driver does an i2c recovery without causing the timeout
if the flag is set.

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 2b76dbfba438..7620bdcdc235 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -334,6 +334,7 @@ struct npcm_i2c {
 	u64 nack_cnt;
 	u64 timeout_cnt;
 	u64 tx_complete_cnt;
+	bool ber_state; /* Indicate the bus error state */
 };
 
 static inline void npcm_i2c_select_bank(struct npcm_i2c *bus,
@@ -1521,6 +1522,7 @@ static void npcm_i2c_irq_handle_ber(struct npcm_i2c *bus)
 	if (npcm_i2c_is_master(bus)) {
 		npcm_i2c_master_abort(bus);
 	} else {
+		bus->ber_state = true;
 		npcm_i2c_clear_master_status(bus);
 
 		/* Clear BB (BUS BUSY) bit */
@@ -1699,6 +1701,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
 		dev_dbg(bus->dev, "bus%d-0x%x recovery skipped, bus not stuck",
 			bus->num, bus->dest_addr);
 		npcm_i2c_reset(bus);
+		bus->ber_state = false;
 		return 0;
 	}
 
@@ -1763,6 +1766,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
 		if (bus->rec_succ_cnt < ULLONG_MAX)
 			bus->rec_succ_cnt++;
 	}
+	bus->ber_state = false;
 	return status;
 }
 
@@ -2158,7 +2162,16 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 
 	} while (time_is_after_jiffies(time_left) && bus_busy);
 
-	if (bus_busy) {
+	/*
+	 * Check the BER (bus error) state, when ber_state is true, it means that the module
+	 * detects the bus error which is caused by some factor like that the electricity
+	 * noise occurs on the bus. Under this condition, the module is reset and the bus
+	 * gets recovered.
+	 *
+	 * While ber_state is false, the module reset and bus recovery also get done as the
+	 * bus is busy.
+	 */
+	if (bus_busy || bus->ber_state) {
 		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
 		npcm_i2c_reset(bus);
 		i2c_recover_bus(adap);
-- 
2.34.1