linux-kernel - [PATCH v2 2/2] serial: sh-sci: Fix deadlock during RSCI FIFO overrun error

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Message-ID: <20251029082101.92156-3-biju.das.jz@bp.renesas.com>
Date: Wed, 29 Oct 2025 08:20:57 +0000
From: Biju <biju.das.au@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>
Cc: Biju Das <biju.das.jz@...renesas.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	Nam Cao <namcao@...utronix.de>,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	Biju Das <biju.das.au@...il.com>,
	linux-renesas-soc@...r.kernel.org,
	stable@...nel.org
Subject: [PATCH v2 2/2] serial: sh-sci: Fix deadlock during RSCI FIFO overrun error

From: Biju Das <biju.das.jz@...renesas.com>

On RSCI IP, a deadlock occurs during a FIFO overrun error, as it uses a
different register to clear the FIFO overrun error status.

Cc: stable@...nel.org
Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
---
v1->v2:
 * Split the fixes patches from original series.
---
 drivers/tty/serial/rsci.c          | 1 +
 drivers/tty/serial/sh-sci-common.h | 1 +
 drivers/tty/serial/sh-sci.c        | 8 ++++++--
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/rsci.c b/drivers/tty/serial/rsci.c
index b3c48dc1e07d..3e1f4b3c4e59 100644
--- a/drivers/tty/serial/rsci.c
+++ b/drivers/tty/serial/rsci.c
@@ -414,6 +414,7 @@ static const struct sci_port_params_bits rsci_port_param_bits = {
 	.rxtx_enable = CCR0_RE | CCR0_TE,
 	.te_clear = CCR0_TE | CCR0_TEIE,
 	.poll_sent_bits = CSR_TDRE | CSR_TEND,
+	.overrun_clr = CFCLR_ORERC,
 };
 
 static const struct sci_port_params rsci_port_params = {
diff --git a/drivers/tty/serial/sh-sci-common.h b/drivers/tty/serial/sh-sci-common.h
index e3c028df14f1..bcdb41ddc15d 100644
--- a/drivers/tty/serial/sh-sci-common.h
+++ b/drivers/tty/serial/sh-sci-common.h
@@ -51,6 +51,7 @@ struct sci_port_params_bits {
 	unsigned int rxtx_enable;
 	unsigned int te_clear;
 	unsigned int poll_sent_bits;
+	unsigned int overrun_clr;
 };
 
 struct sci_common_regs {
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 62bb62b82cbe..b33894d0273b 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1024,8 +1024,12 @@ static int sci_handle_fifo_overrun(struct uart_port *port)
 
 	status = s->ops->read_reg(port, s->params->overrun_reg);
 	if (status & s->params->overrun_mask) {
-		status &= ~s->params->overrun_mask;
-		s->ops->write_reg(port, s->params->overrun_reg, status);
+		if (s->type == SCI_PORT_RSCI) {
+			s->ops->clear_SCxSR(port, s->params->param_bits->overrun_clr);
+		} else {
+			status &= ~s->params->overrun_mask;
+			s->ops->write_reg(port, s->params->overrun_reg, status);
+		}
 
 		port->icount.overrun++;
 
-- 
2.43.0