linux-kernel - [PATCH v3 4/6] i2c: npcm: Modify the client address assignment

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Message-Id: <20240913101445.16513-5-kfting@nuvoton.com>
Date: Fri, 13 Sep 2024 18:14:44 +0800
From: warp5tw@...il.com
To: avifishman70@...il.com,
	tmaimon77@...il.com,
	tali.perry1@...il.com,
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	kfting@...oton.com
Cc: openbmc@...ts.ozlabs.org,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 4/6] i2c: npcm: Modify the client address assignment

From: Tyrone Ting <kfting@...oton.com>

Store the client address earlier since it might get called in
the i2c_recover_bus logic flow at the early stage of the function
npcm_i2c_master_xfer.

Signed-off-by: Tyrone Ting <kfting@...oton.com>
Reviewed-by: Tali Perry <tali.perry1@...il.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 68f3d47323ab..e52e65e63600 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -2155,6 +2155,18 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 
 	} while (time_is_after_jiffies(time_left) && bus_busy);
 
+	/*
+	 * Previously, the address was stored w/o left-shift by one bit and
+	 * with that shift in the following call to npcm_i2c_master_start_xmit.
+	 *
+	 * Since there are cases that the i2c_recover_bus gets called at the
+	 * early stage of the function npcm_i2c_master_xfer, the address is
+	 * stored with the shift and used in the i2c_recover_bus call.
+	 *
+	 * The address is stored from bit 1 to bit 7 in the register for
+	 * sending the i2c address later so it's left-shifted by 1 bit.
+	 */
+	bus->dest_addr = slave_addr << 1;
 	if (bus_busy || bus->ber_state) {
 		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
 		npcm_i2c_reset(bus);
@@ -2163,7 +2175,6 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 	}
 
 	npcm_i2c_init_params(bus);
-	bus->dest_addr = slave_addr;
 	bus->msgs = msgs;
 	bus->msgs_num = num;
 	bus->cmd_err = 0;
-- 
2.34.1