linux-kernel - [PATCH 1/1] i3c: master: svc: skip address resend on repeat START

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Message-Id: <20250416164751.3437085-1-Frank.Li@nxp.com>
Date: Wed, 16 Apr 2025 12:47:50 -0400
From: Frank Li <Frank.Li@....com>
To: Miquel Raynal <miquel.raynal@...tlin.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	linux-i3c@...ts.infradead.org (moderated list:SILVACO I3C DUAL-ROLE MASTER),
	imx@...ts.linux.dev (open list:SILVACO I3C DUAL-ROLE MASTER),
	linux-kernel@...r.kernel.org (open list)
Cc: imx@...ts.linux.dev
Subject: [PATCH 1/1] i3c: master: svc: skip address resend on repeat START

According to the I3C specification, address arbitration only happens during
the START. Repeated START do not initiate arbitration, and In-Band
Interrupts (IBIs) cannot occur at this stage.

Resending the address upon a NACK in a repeat START is therefore redundant
and unnecessary. Avoid redundant retries, improving efficiency and ensuring
protocol compliance.

Signed-off-by: Frank Li <Frank.Li@....com>
---
 drivers/i3c/master/svc-i3c-master.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 85e16de208d3b..5212c2cc6855f 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -1281,9 +1281,9 @@ static int svc_i3c_master_write(struct svc_i3c_master *master,
 static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 			       bool rnw, unsigned int xfer_type, u8 addr,
 			       u8 *in, const u8 *out, unsigned int xfer_len,
-			       unsigned int *actual_len, bool continued)
+			       unsigned int *actual_len, bool continued, bool repeat_start)
 {
-	int retry = 2;
+	int retry = repeat_start ? 1 : 2;
 	u32 reg;
 	int ret;
 
@@ -1468,7 +1468,7 @@ static void svc_i3c_master_start_xfer_locked(struct svc_i3c_master *master)
 		ret = svc_i3c_master_xfer(master, cmd->rnw, xfer->type,
 					  cmd->addr, cmd->in, cmd->out,
 					  cmd->len, &cmd->actual_len,
-					  cmd->continued);
+					  cmd->continued, !!i);
 		/* cmd->xfer is NULL if I2C or CCC transfer */
 		if (cmd->xfer)
 			cmd->xfer->actual_len = cmd->actual_len;
-- 
2.34.1