linux-kernel - [PATCH] i3c: master: svc: add NACK check after start byte sent

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Date:   Wed, 17 May 2023 11:30:30 +0800
From:   Clark Wang <xiaoning.wang@....com>
To:     miquel.raynal@...tlin.com, conor.culhane@...vaco.com,
        alexandre.belloni@...tlin.com
Cc:     linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] i3c: master: svc: add NACK check after start byte sent

Add NACK check after start byte is sent.
It is possible to detect early that a device is not on the bus
and avoid invalid transmissions thereafter.

Signed-off-by: Clark Wang <xiaoning.wang@....com>
---
 drivers/i3c/master/svc-i3c-master.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 4edf33ed207d..0d63b732ef0c 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -92,6 +92,7 @@
 #define SVC_I3C_MINTCLR      0x094
 #define SVC_I3C_MINTMASKED   0x098
 #define SVC_I3C_MERRWARN     0x09C
+#define   SVC_I3C_MERRWARN_NACK BIT(2)
 #define SVC_I3C_MDMACTRL     0x0A0
 #define SVC_I3C_MDATACTRL    0x0AC
 #define   SVC_I3C_MDATACTRL_FLUSHTB BIT(0)
@@ -1014,6 +1015,11 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 	if (ret)
 		goto emit_stop;
 
+	if (readl(master->regs + SVC_I3C_MERRWARN) & SVC_I3C_MERRWARN_NACK) {
+		ret = -ENXIO;
+		goto emit_stop;
+	}
+
 	if (rnw)
 		ret = svc_i3c_master_read(master, in, xfer_len);
 	else
-- 
2.34.1