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Increase the resolution when printing the bitrate error and round-up the
value to 0.01% in the case the resolution would still provide values
which would lead to 0.00%.
Suggested-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20251126-canxl-v8-17-e7e3eb74f889@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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The optimum sample point value depends on the bit symmetry. The more
asymmetric the bit is, the more the sample point would be located
towards the end of the bit. On the contrary, if the transceiver only
has a small asymmetry, the optimal sample point would be slightly
after the centre of the bit.
For NRZ encoding (used by Classical CAN, CAN FD and CAN XL with TMS
off), the optimum sample points values are above 70% as implemented in
can_calc_sample_point_nrz().
When TMS is on, CAN XL optimum sample points are near to 50% or
60% [1]. Add can_calc_sample_point_pwm() which returns a sample point
which is suitable for PWM encoding. We crafted the formula to make it
return the same values as below table (source: table 3 of [1]).
Bit rate (Mbits/s) Sample point
-------------------------------------
2.0 51.3%
5.0 53.1%
8.0 55.0%
10.0 56.3%
12.3 53.8%
13.3 58.3%
14.5 54.5%
16.0 60.0%
17.7 55.6%
20.0 62.5%
The calculation simply consists of setting a slightly too high sample
point and then letting can_update_sample_point() correct the values.
For now, it is just a formula up our sleeves which matches the
empirical observations of [1]. Once CiA recommendations become
available, can_calc_sample_point_pwm() should be updated accordingly.
[1] CAN XL system design: Clock tolerances and edge deviations edge
deviations
Link: https://www.can-cia.org/fileadmin/cia/documents/publications/cnlm/december_2024/cnlm_24-4_p18_can_xl_system_design_clock_tolerances_and_edge_deviations_dr_arthur_mutter_bosch.pdf
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20251126-canxl-v8-14-e7e3eb74f889@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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CAN XL optimal sample point for PWM encoding (when TMS is on) differs
from the NRZ optimal one. There is thus a need to calculate a
different sample point depending whether TMS is on or off.
This is a preparation change: move the sample point calculation from
can_calc_bittiming() into the new can_calc_sample_point_nrz()
function.
In an upcoming change, a function will be added to calculate the
sample point for PWM encoding.
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20251126-canxl-v8-13-e7e3eb74f889@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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The functions can_update_sample_point() and can_calc_bittiming() are
generic and meant to be used for both the nominal and the data bittiming
calculation.
However, those functions use misleading terminologies such as "bitrate
nominal" or "sample point nominal". Replace all places where the word
"nominal" appears with "reference" in order to better distinguish it from
the calculated values.
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20251126-canxl-v8-12-e7e3eb74f889@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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Perform the PWM calculation according to CiA recommendations.
Note that for databitrates greater than 5 MBPS, tqmin is less than
CAN_PWM_NS_MAX (which is defined to 200 nano seconds), consequently,
the result of the division:
DIV_ROUND_UP(xl_ns, CAN_PWM_NS_MAX)
is one and thus the for loop automatically stops on the first
iteration giving a single PWM symbol per bit as expected. Because of
that, there is no actual need for a separate conditional branch for
when the databitrate is greater than 5 MBPS.
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20251126-canxl-v8-10-e7e3eb74f889@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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can_calc_tdco() uses the CAN_CTRLMODE_FD_TDC_MASK and
CAN_CTRLMODE_TDC_AUTO macros making it specific to CAN FD. Add the tdc
mask to the function parameter list. The value of the tdc auto flag
can then be derived from that mask and stored in a local variable.
This way, the function becomes CAN FD agnostic and can be reused later
on for the CAN XL TDC.
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20250923-canxl-netlink-prep-v4-18-e720d28f66fe@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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With the introduction of CAN XL, a new CAN_CTRLMODE_XL_TDC_MASK will
be introduced later on. Because CAN_CTRLMODE_TDC_MASK is not part of
the uapi, rename it to CAN_CTRLMODE_FD_TDC_MASK to make it more
explicit that this mask is meant for CAN FD.
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://patch.msgid.link/20241112165118.586613-10-mailhol.vincent@wanadoo.fr
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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NL_SET_ERR_MSG_FMT()
Replace the netdev_err() by NL_SET_ERR_MSG_FMT() to better inform the
user about the problem. While there, use %u to print unsigned values
and improve error message a bit.
In case of an error, return -EINVAL instead of -EDOM, this corresponds
better to the actual meaning of the error value.
Link: https://lore.kernel.org/all/20230202110854.2318594-17-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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In the current code, if the user configures a bitrate, a default SJW
value of 1 is used. If the user configures both a bitrate and a SJW
value, can_calc_bittiming() silently limits the SJW value to SJW max
and TSEG2.
We came to the conclusion that if the user provided an invalid SJW
value, it's best to bail out and inform the user [1].
[1] https://lore.kernel.org/all/CAMZ6RqKqhmTgUZiwe5uqUjBDnhhC2iOjZ791+Y845btJYwVDKg@mail.gmail.com
Further the ISO 11898-1:2015 standard mandates that "SJW shall be less
than or equal to the minimum of these two items: Phase_Seg1 and
Phase_Seg2." [2] The current code is missing that check.
[2] https://lore.kernel.org/all/BL3PR11MB64844E3FC13C55433CDD0B3DFB449@BL3PR11MB6484.namprd11.prod.outlook.com
The previous patches introduced
1) can_sjw_set_default() - sets a default value for SJW if unset
2) can_sjw_check() - implements a SJW check against SJW max, Phase
Seg1 and Phase Seg2. In the error case this function reports the error
to user space via netlink.
Replace both the open-coded SJW default setting and the open-coded and
insufficient checks of SJW with the helper functions
can_sjw_set_default() and can_sjw_check().
Link: https://lore.kernel.org/all/20230202110854.2318594-16-mkl@pengutronix.de
Link: https://lore.kernel.org/all/CAMZ6RqKqhmTgUZiwe5uqUjBDnhhC2iOjZ791+Y845btJYwVDKg@mail.gmail.com
Link: https://lore.kernel.org/all/BL3PR11MB64844E3FC13C55433CDD0B3DFB449@BL3PR11MB6484.namprd11.prod.outlook.com
Suggested-by: Thomas Kopp <Thomas.Kopp@microchip.com>
Suggested-by: Vincent Mailhol <vincent.mailhol@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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This is a preparation patch.
In order to pass warning/error messages during netlink calls back to
user space, pass the extack struct down the callstack of
can_changelink(), the actual error messages will be added in the
following ptaches.
Link: https://lore.kernel.org/all/20230202110854.2318594-10-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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Commit 1c47fa6b31c2 ("can: dev: add a helper function to calculate the
duration of one bit") added the helper function can_bit_time().
Replace open coded variants of can_bit_time() by the helper function.
Link: https://lore.kernel.org/all/20230202110854.2318594-2-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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The canonical way to select or deselect an object during compilation
is to use this pattern in the relevant Makefile:
bar-$(CONFIG_FOO) := foo.o
bittiming.c instead uses some #ifdef CONFIG_CAN_CALC_BITTIMG.
Create a new file named calc_bittiming.c with all the functions which
are conditionally compiled with CONFIG_CAN_CALC_BITTIMG and modify the
Makefile according to above pattern.
Link: https://lore.kernel.org/all/20220610143009.323579-4-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Acked-by: Max Staudt <max@enpas.org>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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