diff options
| -rw-r--r-- | queue-5.10/serial-sh-sci-increment-the-runtime-usage-counter-for-the-earlycon-device.patch | 85 | ||||
| -rw-r--r-- | queue-5.10/series | 1 |
2 files changed, 86 insertions, 0 deletions
diff --git a/queue-5.10/serial-sh-sci-increment-the-runtime-usage-counter-for-the-earlycon-device.patch b/queue-5.10/serial-sh-sci-increment-the-runtime-usage-counter-for-the-earlycon-device.patch new file mode 100644 index 0000000000..c3dbafdad0 --- /dev/null +++ b/queue-5.10/serial-sh-sci-increment-the-runtime-usage-counter-for-the-earlycon-device.patch @@ -0,0 +1,85 @@ +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> +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 +@@ -3359,6 +3359,22 @@ 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. + */ diff --git a/queue-5.10/series b/queue-5.10/series index b5aa454529..43743d644d 100644 --- a/queue-5.10/series +++ b/queue-5.10/series @@ -319,3 +319,4 @@ net-atm-fix-proc-net-atm-lec-handling.patch arm-dts-am335x-bone-common-add-gpio-phy-reset-on-revision-c3-board.patch arm-dts-am335x-bone-common-increase-mdio-reset-deassert-time.patch arm-dts-am335x-bone-common-increase-mdio-reset-deassert-delay-to-50ms.patch +serial-sh-sci-increment-the-runtime-usage-counter-for-the-earlycon-device.patch |