Kvaser's PCIe cards uses the KCAN FPGA IP block which has dual 4K
buffers for incoming messages shared by all (currently up to eight)
channels. While the driver processes messages in one buffer, new
incoming messages are stored in the other and so on.

The design of KCAN is such that a buffer must be fully read and then
released. Releasing a buffer will make the FPGA switch buffers. If the
other buffer contains at least one incoming message the FPGA will also
instantly issue a new interrupt, if not the interrupt will be issued
after receiving the first new message.

With IRQx interrupts, it takes a little time for the interrupt to
happen, enough for any previous ISR call to do it's business and
return, but MSI interrupts are way faster so this time is reduced to
almost nothing.

So with MSI, releasing the buffer HAS to be the very last action of
the ISR before returning, otherwise the new interrupt might be
"masked" by the kernel because the previous ISR call hasn't returned.
And the interrupts are edge-triggered so we cannot loose one, or the
ping-pong reading process will stop.

This is why this patch modifies the driver to use a single write to
the SRB_CMD register before returning.

Signed-off-by: Martin Jocic <martin.jocic@kvaser.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://patch.msgid.link/20240830153113.2081440-1-martin.jocic@kvaser.com
Fixes: 26ad340e582d ("can: kvaser_pciefd: Add driver for Kvaser PCIEcan devices")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

The mcp251x_hw_wake() function is called with the mpc_lock mutex held and
disables the interrupt handler so that no interrupts can be processed while
waking the device. If an interrupt has already occurred then waiting for
the interrupt handler to complete will deadlock because it will be trying
to acquire the same mutex.

CPU0                           CPU1
----                           ----
mcp251x_open()
 mutex_lock(&priv->mcp_lock)
  request_threaded_irq()
                               <interrupt>
                               mcp251x_can_ist()
                                mutex_lock(&priv->mcp_lock)
  mcp251x_hw_wake()
   disable_irq() <-- deadlock

Use disable_irq_nosync() instead because the interrupt handler does
everything while holding the mutex so it doesn't matter if it's still
running.

Fixes: 8ce8c0abcba3 ("can: mcp251x: only reset hardware as required")
Signed-off-by: Simon Arlott <simon@octiron.net>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/4fc08687-1d80-43fe-9f0d-8ef8475e75f6@0882a8b5-c6c3-11e9-b005-00805fc181fe.uuid.home.arpa
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

When changing the interface from CAN-CC to CAN-FD mode the old
coalescing parameters are re-used. This might cause problem, as the
configured parameters are too big for CAN-FD mode.

During testing an invalid TX coalescing configuration has been seen.
The problem should be been fixed in the previous patch, but add a
safeguard here to ensure that the number of TEF coalescing buffers (if
configured) is exactly the half of all TEF buffers.

Link: https://lore.kernel.org/all/20240805-mcp251xfd-fix-ringconfig-v1-2-72086f0ca5ee@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

If the ring (rx, tx) and/or coalescing parameters (rx-frames-irq,
tx-frames-irq) have been configured while the interface was in CAN-CC
mode, but the interface is brought up in CAN-FD mode, the ring
parameters might be too big.

Use the default CAN-FD values in this case.

Fixes: 9263c2e92be9 ("can: mcp251xfd: ring: add support for runtime configurable RX/TX ring parameters")
Link: https://lore.kernel.org/all/20240805-mcp251xfd-fix-ringconfig-v1-1-72086f0ca5ee@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

The use of coalescing for non-peripheral chips in the current
implementation is limited to non-existing. Disable the possibility to
set coalescing through ethtool.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-8-msp@baylibre.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

To force writing the enabled interrupts, reset the active_interrupts
cache.

Fixes: 07f25091ca02 ("can: m_can: Implement receive coalescing")
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-7-msp@baylibre.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

active_interrupts is a cache for the enabled interrupts and not the
global masking of interrupts. Do not clear this variable otherwise we
may loose the state of the interrupts.

Fixes: 07f25091ca02 ("can: m_can: Implement receive coalescing")
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-6-msp@baylibre.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

On setups without interrupts, the interrupt handler is called from a
timer callback. For non-peripheral receives napi is scheduled,
interrupts are disabled and the timer is canceled with a blocking call.
In case of an error this can happen as well.

Check if napi is scheduled in the timer callback after the interrupt
handler executed. If napi is scheduled, the timer is disabled. It will
be reenabled by m_can_poll().

Return error values from the interrupt handler so that interrupt threads
and timer callback can deal differently with it. In case of the timer
we only disable the timer. The rest will be done when stopping the
interface.

Fixes: b382380c0d2d ("can: m_can: Add hrtimer to generate software interrupt")
Fixes: a163c5761019 ("can: m_can: Start/Cancel polling timer together with interrupts")
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-5-msp@baylibre.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

m_can_rx_peripheral() is a wrapper around m_can_rx_handler() that calls
m_can_disable_all_interrupts() on error. The same handling for the same
error path is done in m_can_isr() as well.

So remove m_can_rx_peripheral() and do the call from m_can_isr()
directly.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-4-msp@baylibre.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

We don't need to disable coalescing when the interrupt handler executes
while the chip is suspended. The coalescing is already reset during
suspend.

Fixes: 07f25091ca02 ("can: m_can: Implement receive coalescing")
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-3-msp@baylibre.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>