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| author | Douglas Anderson <dianders@chromium.org> | 2024-05-31 08:09:18 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-06-04 14:09:47 +0200 |
| commit | ca84cd379b45e9b1775b9e026f069a3a886b409d (patch) | |
| tree | ef20498ddd71ae4ead126016df4dbc8f6d342bec /drivers/tty/serial | |
| parent | 5208e7ced520a813b4f4774451fbac4e517e78b2 (diff) | |
| download | linux-stable-ca84cd379b45e9b1775b9e026f069a3a886b409d.tar.gz linux-stable-ca84cd379b45e9b1775b9e026f069a3a886b409d.tar.bz2 linux-stable-ca84cd379b45e9b1775b9e026f069a3a886b409d.zip | |
serial: port: Don't block system suspend even if bytes are left to xmit
Recently, suspend testing on sc7180-trogdor based devices has started
to sometimes fail with messages like this:
port a88000.serial:0.0: PM: calling pm_runtime_force_suspend+0x0/0xf8 @ 28934, parent: a88000.serial:0
port a88000.serial:0.0: PM: dpm_run_callback(): pm_runtime_force_suspend+0x0/0xf8 returns -16
port a88000.serial:0.0: PM: pm_runtime_force_suspend+0x0/0xf8 returned -16 after 33 usecs
port a88000.serial:0.0: PM: failed to suspend: error -16
I could reproduce these problems by logging in via an agetty on the
debug serial port (which was _not_ used for kernel console) and
running:
cat /var/log/messages
...and then (via an SSH session) forcing a few suspend/resume cycles.
Tracing through the code and doing some printf()-based debugging shows
that the -16 (-EBUSY) comes from the recently added
serial_port_runtime_suspend().
The idea of the serial_port_runtime_suspend() function is to prevent
the port from being _runtime_ suspended if it still has bytes left to
transmit. Having bytes left to transmit isn't a reason to block
_system_ suspend, though. If a serdev device in the kernel needs to
block system suspend it should block its own suspend and it can use
serdev_device_wait_until_sent() to ensure bytes are sent.
The DEFINE_RUNTIME_DEV_PM_OPS() used by the serial_port code means
that the system suspend function will be pm_runtime_force_suspend().
In pm_runtime_force_suspend() we can see that before calling the
runtime suspend function we'll call pm_runtime_disable(). This should
be a reliable way to detect that we're called from system suspend and
that we shouldn't look for busyness.
Fixes: 43066e32227e ("serial: port: Don't suspend if the port is still busy")
Cc: stable@vger.kernel.org
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20240531080914.v3.1.I2395e66cf70c6e67d774c56943825c289b9c13e4@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial')
| -rw-r--r-- | drivers/tty/serial/serial_port.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/tty/serial/serial_port.c b/drivers/tty/serial/serial_port.c index 91a338d3cb34..d35f1d24156c 100644 --- a/drivers/tty/serial/serial_port.c +++ b/drivers/tty/serial/serial_port.c @@ -64,6 +64,13 @@ static int serial_port_runtime_suspend(struct device *dev) if (port->flags & UPF_DEAD) return 0; + /* + * Nothing to do on pm_runtime_force_suspend(), see + * DEFINE_RUNTIME_DEV_PM_OPS. + */ + if (!pm_runtime_enabled(dev)) + return 0; + uart_port_lock_irqsave(port, &flags); if (!port_dev->tx_enabled) { uart_port_unlock_irqrestore(port, flags); |