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The mcp251xfd chip is configured to provide a timestamp with each
received and transmitted CAN frame. The timestamp is derived from the
internal free-running timer, which can also be read from the TBC
register via SPI. The timer is 32 bits wide and is clocked by the
external oscillator (typically 20 or 40 MHz).
To avoid confusion, we call this timestamp "timestamp_raw" or "ts_raw"
for short.
Using the timecounter framework, the "ts_raw" is converted to 64 bit
nanoseconds since the epoch. This is what we call "timestamp".
This is a preparation for the next patches which use the "timestamp"
to work around a bug where so far only the "ts_raw" is used.
Tested-by: Stefan Althöfer <Stefan.Althoefer@janztec.com>
Tested-by: Thomas Kopp <thomas.kopp@microchip.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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mcp251xfd_chip_start/stop()
The mcp251xfd wakes up from Low Power or Sleep Mode when SPI activity
is detected. To avoid this, make sure that the timestamp worker is
stopped before shutting down the chip.
Split the starting of the timestamp worker out of
mcp251xfd_timestamp_init() into the separate function
mcp251xfd_timestamp_start().
Call mcp251xfd_timestamp_init() before mcp251xfd_chip_start(), move
mcp251xfd_timestamp_start() to mcp251xfd_chip_start(). In this way,
mcp251xfd_timestamp_stop() can be called unconditionally by
mcp251xfd_chip_stop().
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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With the patch 07ff4aed015c ("time/timecounter: Mark 1st argument of
timecounter_cyc2time() as const") some instances of the struct
mcp251xfd_priv can be marked as const. This patch marks these as
const.
Link: https://lore.kernel.org/r/20210813091027.159379-1-mkl@pengutronix.de
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Thomas Kopp <thomas.kopp@microchip.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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This patch add the HW timestamping infrastructure. The mcp251xfd has a
free running timer of 32 bit width, running at max 40MHz, which wraps
around every 107 seconds. The current timestamp is latched into RX and
TEF objects automatically be the CAN controller.
This patch sets up a cyclecounter, timecounter and delayed worker
infrastructure (which runs every 45 seconds) to convert the timer into
a proper 64 bit based ns timestamp.
Link: https://lore.kernel.org/r/20210304160328.2752293-6-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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