can: m_can: Implement receive coalescing

m_can offers the possibility to set an interrupt on reaching a watermark
level in the receive FIFO. This can be used to implement coalescing.
Unfortunately there is no hardware timeout available to trigger an
interrupt if only a few messages were received within a given time. To
solve this I am using a hrtimer to wake up the irq thread after x
microseconds.

The timer is always started if receive coalescing is enabled and new
received frames were available during an interrupt. The timer is stopped
if during a interrupt handling no new data was available.

If the timer is started the new item interrupt is disabled and the
watermark interrupt takes over. If the timer is not started again, the
new item interrupt is enabled again, notifying the handler about every
new item received.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240207093220.2681425-5-msp@baylibre.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
index 520e14277dff..b916206199f1 100644
--- a/drivers/net/can/m_can/m_can.h
+++ b/drivers/net/can/m_can/m_can.h
@@ -92,6 +92,11 @@ struct m_can_classdev {
 	int pm_clock_support;
 	int is_peripheral;
 
+	// Cached M_CAN_IE register content
+	u32 active_interrupts;
+	u32 rx_max_coalesced_frames_irq;
+	u32 rx_coalesce_usecs_irq;
+
 	struct mram_cfg mcfg[MRAM_CFG_NUM];
 
 	struct hrtimer hrtimer;