linux.git/drivers/mailbox, branch master

mailbox: imx: Don't force-thread the primary handler

2026-06-21T02:18:39+00:00

The primary interrupt handler (imx_mu_isr()) no longer invokes any
callbacks it only masks the interrupt source and returns. In a
forced-threaded environment the IRQ-core will force-thread the primary
handler which can be avoided.

The primary handler uses a spinlock_t to protect the RMW operation in
imx_mu_xcr_rmw() - nothing that may introduce long latencies.

The lock can be turned into a raw_spinlock_t and then the primary
handler can run in hardirq context even on PREEMPT_RT skipping one
thread.

Make struct imx_mu_priv::xcr_lock a raw_spinlock_t and skip
force-threading the primrary handler by marking it IRQF_NO_THREAD.

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: Move the RXDB part of the mailbox into the threaded handler

2026-06-21T02:18:39+00:00

Move RXDB callback handling into the threaded handler. This similar to
the RX side and since the imx_mu_dcfg::rxdb callback can return an error, the
interrupt is only enabled on success.

Move RXDB callback handling into the threaded handler.

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: Move the RX part of the mailbox into the threaded handler

2026-06-21T02:18:39+00:00

Move RX callback handling into the threaded handler. This is similar to
the TX side except that we explicitly mask the source interrupt in the
primary handler and unmask it in the threaded handler again after
success. This was done automatically in the TX part.

The masking/ unmasking can be removed from imx_mu_specific_rx() since it
already happens in the primary/ threaded handler before invoking the
channel specific callback.

Move RX channel handling into threaded handler.

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: Start splitting the IRQ handler in primary and threaded handler

2026-06-21T02:18:38+00:00

Split the mailbox irq handling into a primary handler (imx_mu_isr()) and
a threaded handler (imx_mu_isr_th()). The primary handler masks the
interrupt event so the threaded handler can run without raising the
interrupt again.

The goal here is to invoke the mailbox core functions (such as
mbox_chan_received_data(), mbox_chan_txdone()) in preemptible context which is
made possible by using an threaded interrupt handler. This in turn means that
mailbox's client callbacks are invoked in preemptible context, too. This then
allows the mailbox client callback to skip an indirection via a workqueue if
it requries preemptible callback.

As a first step, prepare the logic and move TX handling part.

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: Use channel index instead of zero in imx_mu_specific_rx()

2026-06-21T02:18:38+00:00

imx_mu_specific_rx() masks channel 0 and unmasks it again at the end of
the function. Given that at startup the channel index got unmasked it
should do the right job.

This here either unmasks the actual channel or another one but should
have no impact given that it reverses its doing at the end.

Peng Fan commented here:
| For specific rx channel, whether it is i.MX8 SCU or i.MX ELE, actually there is
| only 1 channel as of now, but it seems better to use cp->idx in case more
| channels in future.

Use the channel index instead of zero.

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: use devm_of_platform_populate()

2026-06-21T02:18:38+00:00

The driver uses of_platform_populate() but does not remove the added
devices on removal. This can lead to "double devices" on module removal
followed by adding the module again.

Use devm_of_platform_populate() to remove the populated devices once the
parent device is removed.

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: Use devm_pm_runtime_enable()

2026-06-21T02:18:38+00:00

sashiko complained about early usage of the device while probe isn't
completed. This can be mitigated by delaying the pm_runtime_enable()
into the removal path instead doing it early. This ensures that in an
error case the device is removed (and imx_mu_shutdown()) before
pm_runtime_disable() so we don't have to do this manually.

For the order to work, lets move devm_mbox_controller_register() until
after the pm-runtime part. So the reverse order will be mbox-controller
removal followed by disabling pm runtime.

Use devm_pm_runtime_enable(), remove manual pm_runtime_disable()
invocations and move the pm_runtime handling in probe before
devm_mbox_controller_register().

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: Add a channel shutdown field

2026-06-21T02:18:38+00:00

sashiko complained about possible teardown problem. The scenario

 CPU 0                              CPU 1
  imx_mu_isr()                   imx_mu_shutdown()
                                   imx_mu_xcr_rmw(priv, IMX_MU_RCR, 0, IMX_MU_xCR_RIEn(priv->dcfg->type, cp->idx));
    imx_mu_specific_rx()
      imx_mu_xcr_rmw(priv, IMX_MU_RCR, IMX_MU_xCR_RIEn(priv->dcfg->type, 0), 0);
                                   free_irq()

The RX event remains enabled because in this short window the RX event
was disabled in ->shutdown() while the interrupt was active and then
enabled again by the ISR while ->shutdown waited in free_irq().

This race requires timing and if happens can be problematic on shared
handlers if the "removed" channel triggers an interrupt. In this case
the irq-core will shutdown the interrupt with the "nobody cared"
message.

Introduce imx_mu_con_priv::shutdown to signal that the channel is
shutting down. This flag is set with the lock held (by
imx_mu_xcr_clr_shut()). The unmask side uses imx_mu_xcr_set_act() which
only enables the event if the channel has not been shutdown and
serialises on the same lock.

Reviewed-by: Peng Fan 
Reviewed-by: Mathieu Poirier 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: imx: Forward the timeout/ error in imx_mu_generic_tx()

2026-06-21T02:18:38+00:00

imx_mu_generic_tx() for the IMX_MU_TYPE_TXDB_V2 type polls on a register
which may timeout and is recognized as an error. This error is siltently
dropped and not dropped to the caller.

Forward the error to the caller.

Fixes: b5ef17917f3a7 ("mailbox: imx: fix TXDB_V2 channel race condition")
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Jassi Brar

mailbox: add list of used channels to debugfs

2026-05-18T18:37:28+00:00

During development, it is useful to see which mailboxes are currently
obtained. Use a seq-file in debugfs to list the currently registered
controllers and their used channels. Example output from a Renesas R-Car
X5H based system:

 # cat /sys/kernel/debug/mailbox/mailbox_summary

189e0000.system-controller:
   0: c1000000.mailbox_test_send_to_recv
   1: c1000100.mailbox_test_recv_to_send
 128: c1000100.mailbox_test_recv_to_send
 129: c1000000.mailbox_test_send_to_recv
189e1000.system-controller:
   4: scmi_dev.1
   5: scmi_dev.2

Signed-off-by: Wolfram Sang 
Signed-off-by: Jassi Brar