6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
commit 9f7dea875cc7f9c1a56a5c688290634a59cd1420 upstream.
In the sh-sci driver, sci_ports[0] is used by earlycon. If the earlycon is
still active when sci_probe() is called and the new serial port is supposed
to map to sci_ports[0], return -EBUSY to prevent breaking the earlycon.
This situation should occurs in debug scenarios, and users should be
aware of the potential conflict.
Fixes: 0b0cced19ab1 ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250116182249.3828577-4-claudiu.beznea.uj@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/sh-sci.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -165,6 +165,7 @@ struct sci_port {
static struct sci_port sci_ports[SCI_NPORTS];
static unsigned long sci_ports_in_use;
static struct uart_driver sci_uart_driver;
+static bool sci_uart_earlycon;
static inline struct sci_port *
to_sci_port(struct uart_port *uart)
@@ -3450,6 +3451,7 @@ static int sci_probe_single(struct platf
static int sci_probe(struct platform_device *dev)
{
struct plat_sci_port *p;
+ struct resource *res;
struct sci_port *sp;
unsigned int dev_id;
int ret;
@@ -3479,6 +3481,26 @@ static int sci_probe(struct platform_dev
}
sp = &sci_ports[dev_id];
+
+ /*
+ * In case:
+ * - the probed port alias is zero (as the one used by earlycon), and
+ * - the earlycon is still active (e.g., "earlycon keep_bootcon" in
+ * bootargs)
+ *
+ * defer the probe of this serial. This is a debug scenario and the user
+ * must be aware of it.
+ *
+ * Except when the probed port is the same as the earlycon port.
+ */
+
+ res = platform_get_resource(dev, IORESOURCE_MEM, 0);
+ if (!res)
+ return -ENODEV;
+
+ if (sci_uart_earlycon && sp == &sci_ports[0] && sp->port.mapbase != res->start)
+ return dev_err_probe(&dev->dev, -EBUSY, "sci_port[0] is used by earlycon!\n");
+
platform_set_drvdata(dev, sp);
ret = sci_probe_single(dev, dev_id, p, sp);
@@ -3575,6 +3597,7 @@ static int __init early_console_setup(st
port_cfg.type = type;
sci_ports[0].cfg = &port_cfg;
sci_ports[0].params = sci_probe_regmap(&port_cfg);
+ sci_uart_earlycon = true;
port_cfg.scscr = sci_serial_in(&sci_ports[0].port, SCSCR);
sci_serial_out(&sci_ports[0].port, SCSCR,
SCSCR_RE | SCSCR_TE | port_cfg.scscr);
