--- /dev/null
+From 5f1017069933489add0c08659673443c9905659e Mon Sep 17 00:00:00 2001
+From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+Date: Thu, 16 Jan 2025 20:22:48 +0200
+Subject: serial: sh-sci: Clean sci_ports[0] after at earlycon exit
+
+From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+
+commit 5f1017069933489add0c08659673443c9905659e upstream.
+
+The early_console_setup() function initializes sci_ports[0].port with an
+object of type struct uart_port obtained from the struct earlycon_device
+passed as an argument to early_console_setup().
+
+Later, during serial port probing, the serial port used as earlycon
+(e.g., port A) might be remapped to a different position in the sci_ports[]
+array, and a different serial port (e.g., port B) might be assigned to slot
+0. For example:
+
+sci_ports[0] = port B
+sci_ports[X] = port A
+
+In this scenario, the new port mapped at index zero (port B) retains the
+data associated with the earlycon configuration. Consequently, after the
+Linux boot process, any access to the serial port now mapped to
+sci_ports[0] (port B) will block the original earlycon port (port A).
+
+To address this, introduce an early_console_exit() function to clean up
+sci_ports[0] when earlycon is exited.
+
+To prevent the cleanup of sci_ports[0] while the serial device is still
+being used by earlycon, introduce the struct sci_port::probing flag and
+account for it in early_console_exit().
+
+Fixes: 0b0cced19ab1 ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
+Cc: stable@vger.kernel.org
+Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+Link: https://lore.kernel.org/r/20250116182249.3828577-5-claudiu.beznea.uj@bp.renesas.com
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/tty/serial/sh-sci.c | 32 ++++++++++++++++++++++++++++++--
+ 1 file changed, 30 insertions(+), 2 deletions(-)
+
+--- a/drivers/tty/serial/sh-sci.c
++++ b/drivers/tty/serial/sh-sci.c
+@@ -183,6 +183,7 @@ static struct sci_port sci_ports[SCI_NPO
+ static unsigned long sci_ports_in_use;
+ static struct uart_driver sci_uart_driver;
+ static bool sci_uart_earlycon;
++static bool sci_uart_earlycon_dev_probing;
+
+ static inline struct sci_port *
+ to_sci_port(struct uart_port *uart)
+@@ -3404,7 +3405,8 @@ static struct plat_sci_port *sci_parse_d
+ static int sci_probe_single(struct platform_device *dev,
+ unsigned int index,
+ struct plat_sci_port *p,
+- struct sci_port *sciport)
++ struct sci_port *sciport,
++ struct resource *sci_res)
+ {
+ int ret;
+
+@@ -3451,6 +3453,14 @@ static int sci_probe_single(struct platf
+ sciport->port.flags |= UPF_HARD_FLOW;
+ }
+
++ if (sci_uart_earlycon && sci_ports[0].port.mapbase == sci_res->start) {
++ /*
++ * Skip cleanup the sci_port[0] in early_console_exit(), this
++ * port is the same as the earlycon one.
++ */
++ sci_uart_earlycon_dev_probing = true;
++ }
++
+ return uart_add_one_port(&sci_uart_driver, &sciport->port);
+ }
+
+@@ -3509,7 +3519,7 @@ static int sci_probe(struct platform_dev
+
+ platform_set_drvdata(dev, sp);
+
+- ret = sci_probe_single(dev, dev_id, p, sp);
++ ret = sci_probe_single(dev, dev_id, p, sp, res);
+ if (ret)
+ return ret;
+
+@@ -3666,6 +3676,22 @@ sh_early_platform_init_buffer("earlyprin
+ #ifdef CONFIG_SERIAL_SH_SCI_EARLYCON
+ static struct plat_sci_port port_cfg;
+
++static int early_console_exit(struct console *co)
++{
++ struct sci_port *sci_port = &sci_ports[0];
++
++ /*
++ * Clean the slot used by earlycon. A new SCI device might
++ * map to this slot.
++ */
++ if (!sci_uart_earlycon_dev_probing) {
++ memset(sci_port, 0, sizeof(*sci_port));
++ sci_uart_earlycon = false;
++ }
++
++ return 0;
++}
++
+ static int __init early_console_setup(struct earlycon_device *device,
+ int type)
+ {
+@@ -3683,6 +3709,8 @@ static int __init early_console_setup(st
+ SCSCR_RE | SCSCR_TE | port_cfg.scscr);
+
+ device->con->write = serial_console_write;
++ device->con->exit = early_console_exit;
++
+ return 0;
+ }
+ static int __init sci_early_console_setup(struct earlycon_device *device,
--- /dev/null
+From 651dee03696e1dfde6d9a7e8664bbdcd9a10ea7f Mon Sep 17 00:00:00 2001
+From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+Date: Thu, 16 Jan 2025 20:22:49 +0200
+Subject: serial: sh-sci: Increment the runtime usage counter for the earlycon device
+
+From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+
+commit 651dee03696e1dfde6d9a7e8664bbdcd9a10ea7f upstream.
+
+In the sh-sci driver, serial ports are mapped to the sci_ports[] array,
+with earlycon mapped at index zero.
+
+The uart_add_one_port() function eventually calls __device_attach(),
+which, in turn, calls pm_request_idle(). The identified code path is as
+follows:
+
+uart_add_one_port() ->
+ serial_ctrl_register_port() ->
+ serial_core_register_port() ->
+ serial_core_port_device_add() ->
+ serial_base_port_add() ->
+ device_add() ->
+ bus_probe_device() ->
+ device_initial_probe() ->
+ __device_attach() ->
+ // ...
+ if (dev->p->dead) {
+ // ...
+ } else if (dev->driver) {
+ // ...
+ } else {
+ // ...
+ pm_request_idle(dev);
+ // ...
+ }
+
+The earlycon device clocks are enabled by the bootloader. However, the
+pm_request_idle() call in __device_attach() disables the SCI port clocks
+while earlycon is still active.
+
+The earlycon write function, serial_console_write(), calls
+sci_poll_put_char() via serial_console_putchar(). If the SCI port clocks
+are disabled, writing to earlycon may sometimes cause the SR.TDFE bit to
+remain unset indefinitely, causing the while loop in sci_poll_put_char()
+to never exit. On single-core SoCs, this can result in the system being
+blocked during boot when this issue occurs.
+
+To resolve this, increment the runtime PM usage counter for the earlycon
+SCI device before registering the UART port.
+
+Fixes: 0b0cced19ab1 ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
+Cc: stable@vger.kernel.org
+Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+Link: https://lore.kernel.org/r/20250116182249.3828577-6-claudiu.beznea.uj@bp.renesas.com
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/tty/serial/sh-sci.c | 16 ++++++++++++++++
+ 1 file changed, 16 insertions(+)
+
+--- a/drivers/tty/serial/sh-sci.c
++++ b/drivers/tty/serial/sh-sci.c
+@@ -3455,6 +3455,22 @@ static int sci_probe_single(struct platf
+
+ if (sci_uart_earlycon && sci_ports[0].port.mapbase == sci_res->start) {
+ /*
++ * In case:
++ * - this is the earlycon port (mapped on index 0 in sci_ports[]) and
++ * - it now maps to an alias other than zero and
++ * - the earlycon is still alive (e.g., "earlycon keep_bootcon" is
++ * available in bootargs)
++ *
++ * we need to avoid disabling clocks and PM domains through the runtime
++ * PM APIs called in __device_attach(). For this, increment the runtime
++ * PM reference counter (the clocks and PM domains were already enabled
++ * by the bootloader). Otherwise the earlycon may access the HW when it
++ * has no clocks enabled leading to failures (infinite loop in
++ * sci_poll_put_char()).
++ */
++ pm_runtime_get_noresume(&dev->dev);
++
++ /*
+ * Skip cleanup the sci_port[0] in early_console_exit(), this
+ * port is the same as the earlycon one.
+ */
projects / thirdparty / kernel / stable-queue.git / commitdiff
