The receive error handling code is shared between RSCI and all other
SCIF port types, but the RSCI overrun_reg is specified as a memory
offset, while for other SCIF types it is an enum value used to index
into the sci_port_params->regs array, as mentioned above the
sci_serial_in() function.

For RSCI, the overrun_reg is CSR (0x48), causing the sci_getreg() call
inside the sci_handle_fifo_overrun() function to index outside the
bounds of the regs array, which currently has a size of 20, as specified
by SCI_NR_REGS.

Because of this, we end up accessing memory outside of RSCI's
rsci_port_params structure, which, when interpreted as a plat_sci_reg,
happens to have a non-zero size, causing the following WARN when
sci_serial_in() is called, as the accidental size does not match the
supported register sizes.

The existence of the overrun_reg needs to be checked because
SCIx_SH3_SCIF_REGTYPE has overrun_reg set to SCLSR, but SCLSR is not
present in the regs array.

Avoid calling sci_getreg() for port types which don't use standard
register handling.

Use the ops->read_reg() and ops->write_reg() functions to properly read
and write registers for RSCI, and change the type of the status variable
to accommodate the 32-bit CSR register.

sci_getreg() and sci_serial_in() are also called with overrun_reg in the
sci_mpxed_interrupt() interrupt handler, but that code path is not used
for RSCI, as it does not have a muxed interrupt.

------------[ cut here ]------------
Invalid register access
WARNING: CPU: 0 PID: 0 at drivers/tty/serial/sh-sci.c:522 sci_serial_in+0x38/0xac
Modules linked in: renesas_usbhs at24 rzt2h_adc industrialio_adc sha256 cfg80211 bluetooth ecdh_generic ecc rfkill fuse drm backlight ipv6
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.17.0-rc1+ #30 PREEMPT
Hardware name: Renesas RZ/T2H EVK Board based on r9a09g077m44 (DT)
pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : sci_serial_in+0x38/0xac
lr : sci_serial_in+0x38/0xac
sp : ffff800080003e80
x29: ffff800080003e80 x28: ffff800082195b80 x27: 000000000000000d
x26: ffff8000821956d0 x25: 0000000000000000 x24: ffff800082195b80
x23: ffff000180e0d800 x22: 0000000000000010 x21: 0000000000000000
x20: 0000000000000010 x19: ffff000180e72000 x18: 000000000000000a
x17: ffff8002bcee7000 x16: ffff800080000000 x15: 0720072007200720
x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720
x11: 0000000000000058 x10: 0000000000000018 x9 : ffff8000821a6a48
x8 : 0000000000057fa8 x7 : 0000000000000406 x6 : ffff8000821fea48
x5 : ffff00033ef88408 x4 : ffff8002bcee7000 x3 : ffff800082195b80
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff800082195b80
Call trace:
 sci_serial_in+0x38/0xac (P)
 sci_handle_fifo_overrun.isra.0+0x70/0x134
 sci_er_interrupt+0x50/0x39c
 __handle_irq_event_percpu+0x48/0x140
 handle_irq_event+0x44/0xb0
 handle_fasteoi_irq+0xf4/0x1a0
 handle_irq_desc+0x34/0x58
 generic_handle_domain_irq+0x1c/0x28
 gic_handle_irq+0x4c/0x140
 call_on_irq_stack+0x30/0x48
 do_interrupt_handler+0x80/0x84
 el1_interrupt+0x34/0x68
 el1h_64_irq_handler+0x18/0x24
 el1h_64_irq+0x6c/0x70
 default_idle_call+0x28/0x58 (P)
 do_idle+0x1f8/0x250
 cpu_startup_entry+0x34/0x3c
 rest_init+0xd8/0xe0
 console_on_rootfs+0x0/0x6c
 __primary_switched+0x88/0x90
---[ end trace 0000000000000000 ]---

Cc: stable@vger.kernel.org
Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
---
 drivers/tty/serial/sh-sci.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 538b2f991609..62bb62b82cbe 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1014,16 +1014,18 @@ static int sci_handle_fifo_overrun(struct uart_port *port)
 	struct sci_port *s = to_sci_port(port);
 	const struct plat_sci_reg *reg;
 	int copied = 0;
-	u16 status;
+	u32 status;
 
-	reg = sci_getreg(port, s->params->overrun_reg);
-	if (!reg->size)
-		return 0;
+	if (s->type != SCI_PORT_RSCI) {
+		reg = sci_getreg(port, s->params->overrun_reg);
+		if (!reg->size)
+			return 0;
+	}
 
-	status = sci_serial_in(port, s->params->overrun_reg);
+	status = s->ops->read_reg(port, s->params->overrun_reg);
 	if (status & s->params->overrun_mask) {
 		status &= ~s->params->overrun_mask;
-		sci_serial_out(port, s->params->overrun_reg, status);
+		s->ops->write_reg(port, s->params->overrun_reg, status);
 
 		port->icount.overrun++;
 
-- 
2.51.0

Hi Cosmin,

On Tue, 23 Sept 2025 at 17:47, Cosmin Tanislav
<cosmin-gabriel.tanislav.xa@renesas.com> wrote:
> The receive error handling code is shared between RSCI and all other
> SCIF port types, but the RSCI overrun_reg is specified as a memory
> offset, while for other SCIF types it is an enum value used to index
> into the sci_port_params->regs array, as mentioned above the
> sci_serial_in() function.
>
> For RSCI, the overrun_reg is CSR (0x48), causing the sci_getreg() call
> inside the sci_handle_fifo_overrun() function to index outside the
> bounds of the regs array, which currently has a size of 20, as specified
> by SCI_NR_REGS.
>
> Because of this, we end up accessing memory outside of RSCI's
> rsci_port_params structure, which, when interpreted as a plat_sci_reg,
> happens to have a non-zero size, causing the following WARN when
> sci_serial_in() is called, as the accidental size does not match the
> supported register sizes.
>
> The existence of the overrun_reg needs to be checked because
> SCIx_SH3_SCIF_REGTYPE has overrun_reg set to SCLSR, but SCLSR is not
> present in the regs array.
>
> Avoid calling sci_getreg() for port types which don't use standard
> register handling.
>
> Use the ops->read_reg() and ops->write_reg() functions to properly read
> and write registers for RSCI, and change the type of the status variable
> to accommodate the 32-bit CSR register.
>
> sci_getreg() and sci_serial_in() are also called with overrun_reg in the
> sci_mpxed_interrupt() interrupt handler, but that code path is not used
> for RSCI, as it does not have a muxed interrupt.
>
> ------------[ cut here ]------------
> Invalid register access
> WARNING: CPU: 0 PID: 0 at drivers/tty/serial/sh-sci.c:522 sci_serial_in+0x38/0xac
> Modules linked in: renesas_usbhs at24 rzt2h_adc industrialio_adc sha256 cfg80211 bluetooth ecdh_generic ecc rfkill fuse drm backlight ipv6
> CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.17.0-rc1+ #30 PREEMPT
> Hardware name: Renesas RZ/T2H EVK Board based on r9a09g077m44 (DT)
> pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : sci_serial_in+0x38/0xac
> lr : sci_serial_in+0x38/0xac
> sp : ffff800080003e80
> x29: ffff800080003e80 x28: ffff800082195b80 x27: 000000000000000d
> x26: ffff8000821956d0 x25: 0000000000000000 x24: ffff800082195b80
> x23: ffff000180e0d800 x22: 0000000000000010 x21: 0000000000000000
> x20: 0000000000000010 x19: ffff000180e72000 x18: 000000000000000a
> x17: ffff8002bcee7000 x16: ffff800080000000 x15: 0720072007200720
> x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720
> x11: 0000000000000058 x10: 0000000000000018 x9 : ffff8000821a6a48
> x8 : 0000000000057fa8 x7 : 0000000000000406 x6 : ffff8000821fea48
> x5 : ffff00033ef88408 x4 : ffff8002bcee7000 x3 : ffff800082195b80
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff800082195b80
> Call trace:
>  sci_serial_in+0x38/0xac (P)
>  sci_handle_fifo_overrun.isra.0+0x70/0x134
>  sci_er_interrupt+0x50/0x39c
>  __handle_irq_event_percpu+0x48/0x140
>  handle_irq_event+0x44/0xb0
>  handle_fasteoi_irq+0xf4/0x1a0
>  handle_irq_desc+0x34/0x58
>  generic_handle_domain_irq+0x1c/0x28
>  gic_handle_irq+0x4c/0x140
>  call_on_irq_stack+0x30/0x48
>  do_interrupt_handler+0x80/0x84
>  el1_interrupt+0x34/0x68
>  el1h_64_irq_handler+0x18/0x24
>  el1h_64_irq+0x6c/0x70
>  default_idle_call+0x28/0x58 (P)
>  do_idle+0x1f8/0x250
>  cpu_startup_entry+0x34/0x3c
>  rest_init+0xd8/0xe0
>  console_on_rootfs+0x0/0x6c
>  __primary_switched+0x88/0x90
> ---[ end trace 0000000000000000 ]---
>
> Cc: stable@vger.kernel.org
> Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
> Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>

Thanks for your patch, which is now commit ef8fef45c74b5a00 ("tty:
serial: sh-sci: fix RSCI FIFO overrun handling") in v6.18-rc3.

> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -1014,16 +1014,18 @@ static int sci_handle_fifo_overrun(struct uart_port *port)
>         struct sci_port *s = to_sci_port(port);
>         const struct plat_sci_reg *reg;
>         int copied = 0;
> -       u16 status;
> +       u32 status;
>
> -       reg = sci_getreg(port, s->params->overrun_reg);
> -       if (!reg->size)
> -               return 0;
> +       if (s->type != SCI_PORT_RSCI) {
> +               reg = sci_getreg(port, s->params->overrun_reg);
> +               if (!reg->size)
> +                       return 0;
> +       }
>
> -       status = sci_serial_in(port, s->params->overrun_reg);
> +       status = s->ops->read_reg(port, s->params->overrun_reg);
>         if (status & s->params->overrun_mask) {
>                 status &= ~s->params->overrun_mask;
> -               sci_serial_out(port, s->params->overrun_reg, status);
> +               s->ops->write_reg(port, s->params->overrun_reg, status);
>
>                 port->icount.overrun++;
>

Ouch, this is really becoming fragile, and thus hard to maintain.
See also "[PATCH v2 2/2] serial: sh-sci: Fix deadlock during RSCI FIFO
overrun error".
Are you sure this is the only place where that can happen?
sci_getreg() and sci_serial_{in,out}() are used all over the place.

[1] https://lore.kernel.org/20251029082101.92156-3-biju.das.jz@bp.renesas.com/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

CC Biju, linux-renesas-soc (let's hope for real)

On Thu, 6 Nov 2025 at 17:54, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Cosmin,
>
> On Tue, 23 Sept 2025 at 17:47, Cosmin Tanislav
> <cosmin-gabriel.tanislav.xa@renesas.com> wrote:
> > The receive error handling code is shared between RSCI and all other
> > SCIF port types, but the RSCI overrun_reg is specified as a memory
> > offset, while for other SCIF types it is an enum value used to index
> > into the sci_port_params->regs array, as mentioned above the
> > sci_serial_in() function.
> >
> > For RSCI, the overrun_reg is CSR (0x48), causing the sci_getreg() call
> > inside the sci_handle_fifo_overrun() function to index outside the
> > bounds of the regs array, which currently has a size of 20, as specified
> > by SCI_NR_REGS.
> >
> > Because of this, we end up accessing memory outside of RSCI's
> > rsci_port_params structure, which, when interpreted as a plat_sci_reg,
> > happens to have a non-zero size, causing the following WARN when
> > sci_serial_in() is called, as the accidental size does not match the
> > supported register sizes.
> >
> > The existence of the overrun_reg needs to be checked because
> > SCIx_SH3_SCIF_REGTYPE has overrun_reg set to SCLSR, but SCLSR is not
> > present in the regs array.
> >
> > Avoid calling sci_getreg() for port types which don't use standard
> > register handling.
> >
> > Use the ops->read_reg() and ops->write_reg() functions to properly read
> > and write registers for RSCI, and change the type of the status variable
> > to accommodate the 32-bit CSR register.
> >
> > sci_getreg() and sci_serial_in() are also called with overrun_reg in the
> > sci_mpxed_interrupt() interrupt handler, but that code path is not used
> > for RSCI, as it does not have a muxed interrupt.
> >
> > ------------[ cut here ]------------
> > Invalid register access
> > WARNING: CPU: 0 PID: 0 at drivers/tty/serial/sh-sci.c:522 sci_serial_in+0x38/0xac
> > Modules linked in: renesas_usbhs at24 rzt2h_adc industrialio_adc sha256 cfg80211 bluetooth ecdh_generic ecc rfkill fuse drm backlight ipv6
> > CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.17.0-rc1+ #30 PREEMPT
> > Hardware name: Renesas RZ/T2H EVK Board based on r9a09g077m44 (DT)
> > pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > pc : sci_serial_in+0x38/0xac
> > lr : sci_serial_in+0x38/0xac
> > sp : ffff800080003e80
> > x29: ffff800080003e80 x28: ffff800082195b80 x27: 000000000000000d
> > x26: ffff8000821956d0 x25: 0000000000000000 x24: ffff800082195b80
> > x23: ffff000180e0d800 x22: 0000000000000010 x21: 0000000000000000
> > x20: 0000000000000010 x19: ffff000180e72000 x18: 000000000000000a
> > x17: ffff8002bcee7000 x16: ffff800080000000 x15: 0720072007200720
> > x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720
> > x11: 0000000000000058 x10: 0000000000000018 x9 : ffff8000821a6a48
> > x8 : 0000000000057fa8 x7 : 0000000000000406 x6 : ffff8000821fea48
> > x5 : ffff00033ef88408 x4 : ffff8002bcee7000 x3 : ffff800082195b80
> > x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff800082195b80
> > Call trace:
> >  sci_serial_in+0x38/0xac (P)
> >  sci_handle_fifo_overrun.isra.0+0x70/0x134
> >  sci_er_interrupt+0x50/0x39c
> >  __handle_irq_event_percpu+0x48/0x140
> >  handle_irq_event+0x44/0xb0
> >  handle_fasteoi_irq+0xf4/0x1a0
> >  handle_irq_desc+0x34/0x58
> >  generic_handle_domain_irq+0x1c/0x28
> >  gic_handle_irq+0x4c/0x140
> >  call_on_irq_stack+0x30/0x48
> >  do_interrupt_handler+0x80/0x84
> >  el1_interrupt+0x34/0x68
> >  el1h_64_irq_handler+0x18/0x24
> >  el1h_64_irq+0x6c/0x70
> >  default_idle_call+0x28/0x58 (P)
> >  do_idle+0x1f8/0x250
> >  cpu_startup_entry+0x34/0x3c
> >  rest_init+0xd8/0xe0
> >  console_on_rootfs+0x0/0x6c
> >  __primary_switched+0x88/0x90
> > ---[ end trace 0000000000000000 ]---
> >
> > Cc: stable@vger.kernel.org
> > Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
> > Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
>
> Thanks for your patch, which is now commit ef8fef45c74b5a00 ("tty:
> serial: sh-sci: fix RSCI FIFO overrun handling") in v6.18-rc3.
>
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -1014,16 +1014,18 @@ static int sci_handle_fifo_overrun(struct uart_port *port)
> >         struct sci_port *s = to_sci_port(port);
> >         const struct plat_sci_reg *reg;
> >         int copied = 0;
> > -       u16 status;
> > +       u32 status;
> >
> > -       reg = sci_getreg(port, s->params->overrun_reg);
> > -       if (!reg->size)
> > -               return 0;
> > +       if (s->type != SCI_PORT_RSCI) {
> > +               reg = sci_getreg(port, s->params->overrun_reg);
> > +               if (!reg->size)
> > +                       return 0;
> > +       }
> >
> > -       status = sci_serial_in(port, s->params->overrun_reg);
> > +       status = s->ops->read_reg(port, s->params->overrun_reg);
> >         if (status & s->params->overrun_mask) {
> >                 status &= ~s->params->overrun_mask;
> > -               sci_serial_out(port, s->params->overrun_reg, status);
> > +               s->ops->write_reg(port, s->params->overrun_reg, status);
> >
> >                 port->icount.overrun++;
> >
>
> Ouch, this is really becoming fragile, and thus hard to maintain.
> See also "[PATCH v2 2/2] serial: sh-sci: Fix deadlock during RSCI FIFO
> overrun error".
> Are you sure this is the only place where that can happen?
> sci_getreg() and sci_serial_{in,out}() are used all over the place.
>
> [1] https://lore.kernel.org/20251029082101.92156-3-biju.das.jz@bp.renesas.com/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

CC Biju, linux-renesas-soc

On Thu, 6 Nov 2025 at 17:54, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Cosmin,
>
> On Tue, 23 Sept 2025 at 17:47, Cosmin Tanislav
> <cosmin-gabriel.tanislav.xa@renesas.com> wrote:
> > The receive error handling code is shared between RSCI and all other
> > SCIF port types, but the RSCI overrun_reg is specified as a memory
> > offset, while for other SCIF types it is an enum value used to index
> > into the sci_port_params->regs array, as mentioned above the
> > sci_serial_in() function.
> >
> > For RSCI, the overrun_reg is CSR (0x48), causing the sci_getreg() call
> > inside the sci_handle_fifo_overrun() function to index outside the
> > bounds of the regs array, which currently has a size of 20, as specified
> > by SCI_NR_REGS.
> >
> > Because of this, we end up accessing memory outside of RSCI's
> > rsci_port_params structure, which, when interpreted as a plat_sci_reg,
> > happens to have a non-zero size, causing the following WARN when
> > sci_serial_in() is called, as the accidental size does not match the
> > supported register sizes.
> >
> > The existence of the overrun_reg needs to be checked because
> > SCIx_SH3_SCIF_REGTYPE has overrun_reg set to SCLSR, but SCLSR is not
> > present in the regs array.
> >
> > Avoid calling sci_getreg() for port types which don't use standard
> > register handling.
> >
> > Use the ops->read_reg() and ops->write_reg() functions to properly read
> > and write registers for RSCI, and change the type of the status variable
> > to accommodate the 32-bit CSR register.
> >
> > sci_getreg() and sci_serial_in() are also called with overrun_reg in the
> > sci_mpxed_interrupt() interrupt handler, but that code path is not used
> > for RSCI, as it does not have a muxed interrupt.
> >
> > ------------[ cut here ]------------
> > Invalid register access
> > WARNING: CPU: 0 PID: 0 at drivers/tty/serial/sh-sci.c:522 sci_serial_in+0x38/0xac
> > Modules linked in: renesas_usbhs at24 rzt2h_adc industrialio_adc sha256 cfg80211 bluetooth ecdh_generic ecc rfkill fuse drm backlight ipv6
> > CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.17.0-rc1+ #30 PREEMPT
> > Hardware name: Renesas RZ/T2H EVK Board based on r9a09g077m44 (DT)
> > pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > pc : sci_serial_in+0x38/0xac
> > lr : sci_serial_in+0x38/0xac
> > sp : ffff800080003e80
> > x29: ffff800080003e80 x28: ffff800082195b80 x27: 000000000000000d
> > x26: ffff8000821956d0 x25: 0000000000000000 x24: ffff800082195b80
> > x23: ffff000180e0d800 x22: 0000000000000010 x21: 0000000000000000
> > x20: 0000000000000010 x19: ffff000180e72000 x18: 000000000000000a
> > x17: ffff8002bcee7000 x16: ffff800080000000 x15: 0720072007200720
> > x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720
> > x11: 0000000000000058 x10: 0000000000000018 x9 : ffff8000821a6a48
> > x8 : 0000000000057fa8 x7 : 0000000000000406 x6 : ffff8000821fea48
> > x5 : ffff00033ef88408 x4 : ffff8002bcee7000 x3 : ffff800082195b80
> > x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff800082195b80
> > Call trace:
> >  sci_serial_in+0x38/0xac (P)
> >  sci_handle_fifo_overrun.isra.0+0x70/0x134
> >  sci_er_interrupt+0x50/0x39c
> >  __handle_irq_event_percpu+0x48/0x140
> >  handle_irq_event+0x44/0xb0
> >  handle_fasteoi_irq+0xf4/0x1a0
> >  handle_irq_desc+0x34/0x58
> >  generic_handle_domain_irq+0x1c/0x28
> >  gic_handle_irq+0x4c/0x140
> >  call_on_irq_stack+0x30/0x48
> >  do_interrupt_handler+0x80/0x84
> >  el1_interrupt+0x34/0x68
> >  el1h_64_irq_handler+0x18/0x24
> >  el1h_64_irq+0x6c/0x70
> >  default_idle_call+0x28/0x58 (P)
> >  do_idle+0x1f8/0x250
> >  cpu_startup_entry+0x34/0x3c
> >  rest_init+0xd8/0xe0
> >  console_on_rootfs+0x0/0x6c
> >  __primary_switched+0x88/0x90
> > ---[ end trace 0000000000000000 ]---
> >
> > Cc: stable@vger.kernel.org
> > Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
> > Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
>
> Thanks for your patch, which is now commit ef8fef45c74b5a00 ("tty:
> serial: sh-sci: fix RSCI FIFO overrun handling") in v6.18-rc3.
>
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -1014,16 +1014,18 @@ static int sci_handle_fifo_overrun(struct uart_port *port)
> >         struct sci_port *s = to_sci_port(port);
> >         const struct plat_sci_reg *reg;
> >         int copied = 0;
> > -       u16 status;
> > +       u32 status;
> >
> > -       reg = sci_getreg(port, s->params->overrun_reg);
> > -       if (!reg->size)
> > -               return 0;
> > +       if (s->type != SCI_PORT_RSCI) {
> > +               reg = sci_getreg(port, s->params->overrun_reg);
> > +               if (!reg->size)
> > +                       return 0;
> > +       }
> >
> > -       status = sci_serial_in(port, s->params->overrun_reg);
> > +       status = s->ops->read_reg(port, s->params->overrun_reg);
> >         if (status & s->params->overrun_mask) {
> >                 status &= ~s->params->overrun_mask;
> > -               sci_serial_out(port, s->params->overrun_reg, status);
> > +               s->ops->write_reg(port, s->params->overrun_reg, status);
> >
> >                 port->icount.overrun++;
> >
>
> Ouch, this is really becoming fragile, and thus hard to maintain.
> See also "[PATCH v2 2/2] serial: sh-sci: Fix deadlock during RSCI FIFO
> overrun error".
> Are you sure this is the only place where that can happen?
> sci_getreg() and sci_serial_{in,out}() are used all over the place.
>
> [1] https://lore.kernel.org/20251029082101.92156-3-biju.das.jz@bp.renesas.com/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds