This patch adds RX IRQ coalescing support to the driver.
The mcp251xfd chip doesn't support proper hardware based coalescing,
so this patch tries to implemented it in software. The RX-FIFO offers
a "FIFO not empty" interrupt, which is used if no coalescing is
active.
With activated RX IRQ coalescing the "FIFO not empty" interrupt is
disabled in the RX IRQ handler and the "FIFO half full" or "FIFO full
interrupt" (depending on RX max coalesced frames IRQ) is used instead.
To avoid RX CAN frame starvation a hrtimer is setup with RX coalesce
usecs IRQ,on timer expiration the "FIFO not empty" is enabled again.
Support for ethtool configuration is added in the next patch.
Link: https://lore.kernel.org/20220313083640.501791-9-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
So far the configuration of the hardware FIFOs is hard coded and
depend only on the selected CAN mode (CAN-2.0 or CAN-FD).
This patch updates the macros describing the ring, FIFO and RAM layout
to prepare for the next patches that add support for runtime
configurable ring parameters via ethtool.
Link: https://lore.kernel.org/20220313083640.501791-7-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This patch prepares the driver to use more than one RX-FIFO. Having a
bigger RX buffer is beneficial in high load situations, where the
system temporarily cannot keep up reading CAN frames from the chip.
Using a bigger RX buffer also allows to implement RX IRQ coalescing,
which will be added in a later patch series.
If using more than 1 RX-FIFO the driver has to figure out, which FIFOs
have RX'ed CAN frames pending. This is indicated by a set bit in the
RXIF register, which is positioned directly after the interrupt status
register INT. If more than 1 RX-FIFO is used, the driver reads both
registers in 1 transfer.
The mcp251xfd_handle_rxif() function iterates over all RX rings and
reads out the RX'ed CAN frames for for all pending FIFOs. To keep the
logic for the 1 RX-FIFO only case in mcp251xfd_handle_rxif() simple,
the driver marks that FIFO pending in mcp251xfd_ring_init().
The chip has a dedicated RX interrupt line to signal pending RX'ed
frames. If connected to an input GPIO and the driver will skip the
initial read of the interrupt status register (INT) and directly read
the pending RX'ed frames if the line is active. The driver assumes the
1st RX-FIFO pending (a read of the RXIF register would re-introduce
the skipped initial read of the INT register). Any other pending
RX-FIFO will be served in the main interrupt handler.
Link: https://lore.kernel.org/all/20220217103826.2299157-8-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
The recent change of the order of the TX and RX FIFOs is not reflected
in the debug info of the FIFO setup. This patch adjust the order and
additionally prints the base address of each FIFO.
Since the mcp251xfd_ring_init() may fail due to wrongly configured
FIFOs, printing of the FIFO setup is moved there. In case of an error
it would not be printed in mcp251xfd_ring_init().
Link: https://lore.kernel.org/all/20220217103826.2299157-7-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
With this patch the usage of the on-chip RAM is checked. In the
current driver the FIFO setup is fixed and always fits into the RAM.
With an upcoming patch series the ring and FIFO setup will be more
dynamic. Although using more RAM than available should not happen, but
add this safety check, just in case.
Link: https://lore.kernel.org/all/20220217103826.2299157-6-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This patch actually changes the order of the TX and RX FIFOs.
This gives the opportunity to minimize the number of SPI transfers in
the IRQ handler. The read of the IRQ status register and RX FIFO
status registers can be combined into single SPI transfer. If the RX
ring uses FIFO 1, the overall length of the transfer is smaller than
in the original layout, where the RX FIFO comes after the TX FIFO.
Link: https://lore.kernel.org/all/20220217103826.2299157-5-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This patch improves the initialization of the TX and RX rings. The
initialization functions are now called with pointers to the next free
address (in the on chip RAM) and next free hardware FIFO. The rings
are initialized using these values and the pointers are modified to
point to the next free elements.
This means the order of the mcp251xfd_ring_init_*() functions
specifies the order of the rings in the hardware FIFO. This makes it
possible to change the order of the TX and RX FIFOs, which is done in
the next patch.
This gives the opportunity to minimize the number of SPI transfers in
the IRQ handler. The read of the IRQ status register and RX FIFO
status registers can be combined into single SPI transfer. If the RX
ring uses FIFO 1, the overall length of the transfer is smaller than
in the original layout, where the RX FIFO comes after the TX FIFO.
Link: https://lore.kernel.org/all/20220217103826.2299157-4-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This patch removes the hard coded assumption that the TX ring uses
hardware FIFO 1. This allows the hardware FIFO 1 to be used for RX and
the next free FIFO for TX.
This gives the opportunity to minimize the number of SPI transfers in
the IRQ handler. The read of the IRQ status register and RX FIFO
status registers can be combined into single SPI transfer. If the RX
ring uses FIFO 1, the overall length of the transfer is smaller than
in the original layout, where the RX FIFO comes after the TX FIFO.
Link: https://lore.kernel.org/all/20220217103826.2299157-2-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
