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@kernel.org
Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
---
 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

On Mon, Oct 27, 2025 at 03:45:51PM +0000, Biju Das wrote:
> 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@kernel.org
> Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>

Why is patch 4/19 the only one marked for stable backports?  That feels
really wrong as that will not show up until after 6.19-rc1 is out, AND
the dependant patches will also not be backported.

Please split up patch series to have "things that must be merged now"
separate from "these are for the next -rc1 release"

thanks,

greg k-h