linux-kernel - [PATCH 2/6] i3c: master: svc: fix wrong data return when IBI happen during start frame

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Date:   Mon, 16 Oct 2023 11:32:28 -0400
From:   Frank Li <Frank.Li@....com>
To:     miquel.raynal@...tlin.com, conor.culhane@...vaco.com,
        alexandre.belloni@...tlin.com, joe@...ches.com,
        linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org,
        imx@...ts.linux.dev
Subject: [PATCH 2/6] i3c: master: svc: fix wrong data return when IBI happen during start frame

     ┌─────┐     ┏──┐  ┏──┐  ┏──┐  ┏──┐  ┏──┐  ┏──┐  ┏──┐  ┏──┐  ┌─────
SCL: ┘     └─────┛  └──┛  └──┛  └──┛  └──┛  └──┛  └──┛  └──┛  └──┘
     ───┐                       ┌─────┐     ┌─────┐     ┌───────────┐
SDA:    └───────────────────────┘     └─────┘     └─────┘           └─────
     xxx╱    ╲╱                                        ╲╱    ╲╱    ╲╱    ╲
   : xxx╲IBI ╱╲               Addr(0x0a)               ╱╲ RW ╱╲NACK╱╲ S  ╱

In-Band Interrupt (IBI) occurred and IBI work thread may not to be
scheduled. When svc_i3c_master_priv_xfers() initiates the I3C transfer
frame and attempts to send address 0x7e, the target interprets it as an
IBI handler and returns the target address 0x0a.

However, svc_i3c_master_priv_xfers() does not handle this case and proceeds
with other transfers, resulting in incorrect data being returned.

IBIWON check has been added in svc_i3c_master_xfer(). In case this
situation occurs, a failure is now returned to the driver.

Fixes: dd3c52846d59 ("i3c: master: svc: Add Silvaco I3C master driver")
Cc: stable@...r.kernel.org
Signed-off-by: Frank Li <Frank.Li@....com>
---
 drivers/i3c/master/svc-i3c-master.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index ebdb3ea1af9d..0f57a5f75e39 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -1009,6 +1009,9 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 	u32 reg;
 	int ret;
 
+	/* clean SVC_I3C_MINT_IBIWON w1c bits */
+	writel(SVC_I3C_MINT_IBIWON, master->regs + SVC_I3C_MSTATUS);
+
 	writel(SVC_I3C_MCTRL_REQUEST_START_ADDR |
 	       xfer_type |
 	       SVC_I3C_MCTRL_IBIRESP_NACK |
@@ -1027,6 +1030,23 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 		goto emit_stop;
 	}
 
+	/*
+	 * According to I3C spec ver 1.1.1, 5.1.2.2.3 Consequence of Controller Starting a Frame
+	 * with I3C Target Address.
+	 *
+	 * The I3C Controller normally should start a Frame, the Address may be arbitrated, and so
+	 * the Controller shall monitor to see whether an In-Band Interrupt request, a Controller
+	 * Role Request (i.e., Secondary Controller requests to become the Active Controller), or
+	 * a Hot-Join Request has been made.
+	 *
+	 * If missed IBIWON check, the wrong data will be return. When IBIWON happen, return falure
+	 * and yeild the above events handler.
+	 */
+	if (SVC_I3C_MSTATUS_IBIWON(reg)) {
+		ret = -ENXIO;
+		goto emit_stop;
+	}
+
 	if (rnw)
 		ret = svc_i3c_master_read(master, in, xfer_len);
 	else
-- 
2.34.1