[PATCH 0/6] tty: serial: propagate errors from uart_ops.pm callback

[Praveen Talari <praveen.talari@oss.qualcomm.com>]

The uart_ops.pm callback has been declared void since its introduction,
which means any error from a driver's power management implementation is
silently discarded by uart_change_pm(). Beyond losing the error
information, uart_change_pm() unconditionally updates state->pm_state
even when the underlying hardware transition failed. This causes the
serial core to track a power state that does not reflect reality:
subsequent calls to uart_change_pm() see the stale cached state as
matching the requested state and skip the callback entirely, leaving the
hardware permanently stuck with no further recovery attempt.

On modern platforms where the .pm callback performs real work —
enabling clock trees, interacting with runtime PM, asserting voltage
regulators — this is a correctness gap. Failures are invisible to the
PM framework, the port proceeds to call ops->startup() on potentially
unpowered hardware, and suspend/resume errors are hidden from the core
that needs to handle them.

This series fixes the problem in four steps:

  Patch 1 changes the uart_ops.pm callback signature from void to int,
  updates uart_change_pm() to propagate errors and only commit
  state->pm_state on success, and handles the return value at every
  call site in serial_core.c with appropriate policy per context
  (propagate, log, or skip-on-failure).

  Patch 2 updates the 8250 driver family: serial8250_do_pm() and
  serial8250_pm() are updated to return int (with the exported symbol
  declaration updated in serial_8250.h), and the 8250 sub-driver
  pm callbacks are updated to return 0.

  Patch 3 updates the remaining non-8250 serial drivers. All .pm
  implementations are updated to return 0. The sh-sci forward
  declaration shared with rsci is also updated.

  Patch 4 updates arch-level implementations: SA1100 (assabet, h3xxx),
  OMAP1/ams-delta (modem_pm, now propagates regulator errors), and
  MIPS/Alchemy (alchemy_8250_pm).

All existing .pm implementations return 0, so there is no functional
change for any current driver. The series purely adds the infrastructure
for drivers to report errors going forward, with the serial core ready
to handle them correctly.

Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
---
Praveen Talari (6):
      tty: serial: change uart_ops.pm callback to return int
      serial: 8250: update .pm callbacks to return int
      tty: serial: update .pm callbacks to return int
      arch: update uart pm callbacks to return int
      tty: serial: propagate uart_configure_port failure to uart_add_one_port
      serial: qcom-geni: check return value of pm_runtime_resume_and_get()

 arch/arm/mach-omap1/board-ams-delta.c       |  10 +--
 arch/arm/mach-sa1100/assabet.c              |   3 +-
 arch/arm/mach-sa1100/h3xxx.c                |   3 +-
 arch/mips/alchemy/common/platform.c         |   5 +-
 drivers/tty/serial/8250/8250_dw.c           |   3 +-
 drivers/tty/serial/8250/8250_exar.c         |   4 +-
 drivers/tty/serial/8250/8250_mtk.c          |   4 +-
 drivers/tty/serial/8250/8250_omap.c         |   6 +-
 drivers/tty/serial/8250/8250_port.c         |   9 ++-
 drivers/tty/serial/8250/8250_pxa.c          |   6 +-
 drivers/tty/serial/atmel_serial.c           |   5 +-
 drivers/tty/serial/fsl_lpuart.c             |   3 +-
 drivers/tty/serial/msm_serial.c             |   5 +-
 drivers/tty/serial/omap-serial.c            |   3 +-
 drivers/tty/serial/pxa.c                    |   3 +-
 drivers/tty/serial/qcom_geni_serial.c       |  16 +++--
 drivers/tty/serial/samsung_tty.c            |   5 +-
 drivers/tty/serial/sc16is7xx.c              |   5 +-
 drivers/tty/serial/serial_core.c            | 104 ++++++++++++++++++++--------
 drivers/tty/serial/serial_txx9.c            |   3 +-
 drivers/tty/serial/sh-sci-common.h          |   4 +-
 drivers/tty/serial/sh-sci.c                 |   5 +-
 drivers/tty/serial/sprd_serial.c            |   5 +-
 drivers/tty/serial/st-asc.c                 |   5 +-
 drivers/tty/serial/stm32-usart.c            |   5 +-
 drivers/tty/serial/uartlite.c               |   5 +-
 drivers/tty/serial/xilinx_uartps.c          |   5 +-
 include/linux/platform_data/sa11x0-serial.h |   2 +-
 include/linux/serial_8250.h                 |   6 +-
 include/linux/serial_core.h                 |  10 +--
 30 files changed, 171 insertions(+), 86 deletions(-)
---
base-commit: 8cdeaa50eae8dad34885515f62559ee83e7e8dda
change-id: 20260706-add_return_check_for_uart_change_pm-d2cb365202f3

Best regards,
--  
Praveen Talari <praveen.talari@oss.qualcomm.com>