linux-stable.git/drivers/net/can/dev, branch linux-5.17.y

can: netlink: report the CAN controller mode supported flags

2022-01-05T11:09:06+00:00

Currently, the CAN netlink interface provides no easy ways to check
the capabilities of a given controller. The only method from the
command line is to try each CAN_CTRLMODE_* individually to check
whether the netlink interface returns an -EOPNOTSUPP error or not
(alternatively, one may find it easier to directly check the source
code of the driver instead...)

This patch introduces a method for the user to check both the
supported and the static capabilities. The proposed method introduces
a new IFLA nest: IFLA_CAN_CTRLMODE_EXT which extends the current
IFLA_CAN_CTRLMODE. This is done to guaranty a full forward and
backward compatibility between the kernel and the user land
applications.

The IFLA_CAN_CTRLMODE_EXT nest contains one single entry:
IFLA_CAN_CTRLMODE_SUPPORTED. Because this entry is only used in one
direction: kernel to userland, no new struct nla_policy are
introduced.

Below table explains how IFLA_CAN_CTRLMODE_SUPPORTED (hereafter:
"supported") and can_ctrlmode::flags (hereafter: "flags") allow us to
identify both the supported and the static capabilities, when masked
with any of the CAN_CTRLMODE_* bit flags:

 supported &	flags &		Controller capabilities
 CAN_CTRLMODE_*	CAN_CTRLMODE_*
 -----------------------------------------------------------------------
 false		false		Feature not supported (always disabled)
 false		true		Static feature (always enabled)
 true		false		Feature supported but disabled
 true		true		Feature supported and enabled

Link: https://lore.kernel.org/all/20211213160226.56219-5-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: dev: replace can_priv::ctrlmode_static by can_get_static_ctrlmode()

2022-01-05T11:09:05+00:00

The statically enabled features of a CAN controller can be retrieved
using below formula:

| u32 ctrlmode_static = priv->ctrlmode & ~priv->ctrlmode_supported;

As such, there is no need to store this information. This patch remove
the field ctrlmode_static of struct can_priv and provides, in
replacement, the inline function can_get_static_ctrlmode() which
returns the same value.

Link: https://lore.kernel.org/all/20211213160226.56219-2-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: do not increase rx_bytes statistics for RTR frames

2022-01-05T11:09:05+00:00

The actual payload length of the CAN Remote Transmission Request (RTR)
frames is always 0, i.e. no payload is transmitted on the wire.
However, those RTR frames still use the DLC to indicate the length of
the requested frame.

As such, net_device_stats::rx_bytes should not be increased for the
RTR frames.

This patch fixes all the CAN drivers.

Link: https://lore.kernel.org/all/20211207121531.42941-5-mailhol.vincent@wanadoo.fr
Cc: Marc Kleine-Budde 
Cc: Nicolas Ferre 
Cc: Alexandre Belloni 
Cc: Ludovic Desroches 
Cc: Chandrasekar Ramakrishnan 
Cc: Maxime Ripard 
Cc: Chen-Yu Tsai 
Cc: Jernej Skrabec 
Cc: Yasushi SHOJI 
Cc: Appana Durga Kedareswara rao 
Cc: Naga Sureshkumar Relli 
Cc: Michal Simek 
Cc: Stephane Grosjean 
Tested-by: Jimmy Assarsson  # kvaser
Signed-off-by: Vincent Mailhol 
Acked-by: Stefan Mätje  # esd_usb2
Tested-by: Stefan Mätje  # esd_usb2
Signed-off-by: Marc Kleine-Budde

can: do not increase rx statistics when generating a CAN rx error message frame

2022-01-05T11:09:05+00:00

The CAN error message frames (i.e. error skb) are an interface
specific to socket CAN. The payload of the CAN error message frames
does not correspond to any actual data sent on the wire. Only an error
flag and a delimiter are transmitted when an error occurs (c.f. ISO
11898-1 section 10.4.4.2 "Error flag").

For this reason, it makes no sense to increment the rx_packets and
rx_bytes fields of struct net_device_stats because no actual payload
were transmitted on the wire.

This patch fixes all the CAN drivers.

Link: https://lore.kernel.org/all/20211207121531.42941-2-mailhol.vincent@wanadoo.fr
CC: Marc Kleine-Budde 
CC: Nicolas Ferre 
CC: Alexandre Belloni 
CC: Ludovic Desroches 
CC: Chandrasekar Ramakrishnan 
CC: Maxime Ripard 
CC: Chen-Yu Tsai 
CC: Jernej Skrabec 
CC: Appana Durga Kedareswara rao 
CC: Naga Sureshkumar Relli 
CC: Michal Simek 
CC: Stephane Grosjean 
Tested-by: Jimmy Assarsson  # kvaser
Signed-off-by: Vincent Mailhol 
Acked-by: Stefan Mätje  # esd_usb2
Tested-by: Stefan Mätje  # esd_usb2
Signed-off-by: Marc Kleine-Budde

can: bittiming: replace CAN units with the generic ones from linux/units.h

2021-12-08T09:12:58+00:00

In [1], we introduced a set of units in linux/can/bittiming.h. Since
then, generic SI prefixes were added to linux/units.h in [2]. Those
new prefixes can perfectly replace CAN specific ones.

This patch replaces all occurrences of the CAN units with their
corresponding prefix (from linux/units) and the unit (as a comment)
according to below table.

 CAN units	SI metric prefix (from linux/units) + unit (as a comment)
 ------------------------------------------------------------------------
 CAN_KBPS	KILO /* BPS */
 CAN_MBPS	MEGA /* BPS */
 CAM_MHZ	MEGA /* Hz */

The definition are then removed from linux/can/bittiming.h

[1] commit 1d7750760b70 ("can: bittiming: add CAN_KBPS, CAN_MBPS and
CAN_MHZ macros")

[2] commit 26471d4a6cf8 ("units: Add SI metric prefix definitions")

Link: https://lore.kernel.org/all/20211124014536.782550-1-mailhol.vincent@wanadoo.fr
Suggested-by: Jimmy Assarsson 
Suggested-by: Oliver Hartkopp 
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: netlink: add can_priv::do_get_auto_tdcv() to retrieve tdcv from device

2021-10-24T14:24:29+00:00

Some CAN device can measure the TDCV (Transmission Delay Compensation
Value) automatically for each transmitted CAN frames.

A callback function do_get_auto_tdcv() is added to retrieve that
value. This function is used only if CAN_CTRLMODE_TDC_AUTO is enabled
(if CAN_CTRLMODE_TDC_MANUAL is selected, the TDCV value is provided by
the user).

If the device does not support reporting of TDCV, do_get_auto_tdcv()
should be set to NULL and TDCV will not be reported by the netlink
interface.

On success, do_get_auto_tdcv() shall return 0. If the value can not be
measured by the device, for example because network is down or because
no frames were transmitted yet, can_priv::do_get_auto_tdcv() shall
return a negative error code (e.g. -EINVAL) to signify that the value
is not yet available. In such cases, TDCV is not reported by the
netlink interface.

Link: https://lore.kernel.org/all/20210918095637.20108-6-mailhol.vincent@wanadoo.fr
CC: Stefan Mätje 
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: netlink: add interface for CAN-FD Transmitter Delay Compensation (TDC)

2021-10-24T14:24:29+00:00

Add the netlink interface for TDC parameters of struct can_tdc_const
and can_tdc.

Contrary to the can_bittiming(_const) structures for which there is
just a single IFLA_CAN(_DATA)_BITTMING(_CONST) entry per structure,
here, we create a nested entry IFLA_CAN_TDC. Within this nested entry,
additional IFLA_CAN_TDC_TDC* entries are added for each of the TDC
parameters of the newly introduced struct can_tdc_const and struct
can_tdc.

For struct can_tdc_const, these are:
        IFLA_CAN_TDC_TDCV_MIN
        IFLA_CAN_TDC_TDCV_MAX
        IFLA_CAN_TDC_TDCO_MIN
        IFLA_CAN_TDC_TDCO_MAX
        IFLA_CAN_TDC_TDCF_MIN
        IFLA_CAN_TDC_TDCF_MAX

For struct can_tdc, these are:
        IFLA_CAN_TDC_TDCV
        IFLA_CAN_TDC_TDCO
        IFLA_CAN_TDC_TDCF

This is done so that changes can be applied in the future to the
structures without breaking the netlink interface.

The TDC netlink logic works as follow:

 * CAN_CTRLMODE_FD is not provided:
    - if any TDC parameters are provided: error.

    - TDC parameters not provided: TDC parameters unchanged.

 * CAN_CTRLMODE_FD is provided and is false:
     - TDC is deactivated: both the structure and the
       CAN_CTRLMODE_TDC_{AUTO,MANUAL} flags are flushed.

 * CAN_CTRLMODE_FD provided and is true:
    - CAN_CTRLMODE_TDC_{AUTO,MANUAL} and tdc{v,o,f} not provided: call
      can_calc_tdco() to automatically decide whether TDC should be
      activated and, if so, set CAN_CTRLMODE_TDC_AUTO and uses the
      calculated tdco value.

    - CAN_CTRLMODE_TDC_AUTO and tdco provided: set
      CAN_CTRLMODE_TDC_AUTO and use the provided tdco value. Here,
      tdcv is illegal and tdcf is optional.

    - CAN_CTRLMODE_TDC_MANUAL and both of tdcv and tdco provided: set
      CAN_CTRLMODE_TDC_MANUAL and use the provided tdcv and tdco
      value. Here, tdcf is optional.

    - CAN_CTRLMODE_TDC_{AUTO,MANUAL} are mutually exclusive. Whenever
      one flag is turned on, the other will automatically be turned
      off. Providing both returns an error.

    - Combination other than the one listed above are illegal and will
      return an error.

N.B. above rules mean that whenever CAN_CTRLMODE_FD is provided, the
previous TDC values will be overwritten. The only option to reuse
previous TDC value is to not provide CAN_CTRLMODE_FD.

All the new parameters are defined as u32. This arbitrary choice is
done to mimic the other bittiming values with are also all of type
u32. An u16 would have been sufficient to hold the TDC values.

This patch completes below series (c.f. [1]):
  - commit 289ea9e4ae59 ("can: add new CAN FD bittiming parameters:
    Transmitter Delay Compensation (TDC)")
  - commit c25cc7993243 ("can: bittiming: add calculation for CAN FD
    Transmitter Delay Compensation (TDC)")

[1] https://lore.kernel.org/linux-can/20210224002008.4158-1-mailhol.vincent@wanadoo.fr/T/#t

Link: https://lore.kernel.org/all/20210918095637.20108-5-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: bittiming: change can_calc_tdco()'s prototype to not directly modify priv

2021-10-24T14:24:29+00:00

The function can_calc_tdco() directly retrieves can_priv from the
net_device and directly modifies it.

This is annoying for the upcoming patch. In
drivers/net/can/dev/netlink.c:can_changelink(), the data bittiming are
written to a temporary structure and memcpyed to can_priv only after
everything succeeded. In the next patch, where we will introduce the
netlink interface for TDC parameters, we will add a new TDC block
which can potentially fail. For this reason, the data bittiming
temporary structure has to be copied after that to-be-introduced TDC
block. However, TDC also needs to access data bittiming information.

We change the prototype so that the data bittiming structure is passed
to can_calc_tdco() as an argument instead of retrieving it from
priv. This way can_calc_tdco() can access the data bittiming before it
gets memcpyed to priv.

Link: https://lore.kernel.org/all/20210918095637.20108-4-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: bittiming: change unit of TDC parameters to clock periods

2021-10-24T14:24:28+00:00

In the current implementation, all Transmission Delay Compensation
(TDC) parameters are expressed in time quantum. However, ISO 11898-1
actually specifies that these should be expressed in *minimum* time
quantum.

Furthermore, the minimum time quantum is specified to be "one node
clock period long" (c.f. paragraph 11.3.1.1 "Bit time"). For sake of
simplicity, we prefer to use the "clock period" term instead of
"minimum time quantum" because we believe that it is more broadly
understood.

This patch fixes that discrepancy by updating the documentation and
the formula for TDCO calculation.

N.B. In can_calc_tdco(), the sample point (in time quantum) was
calculated using a division, thus introducing a risk of rounding and
truncation errors. On top of changing the unit to clock period, we
also modified the formula to use only additions.

Link: https://lore.kernel.org/all/20210918095637.20108-3-mailhol.vincent@wanadoo.fr
Suggested-by: Stefan Mätje 
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: bittiming: allow TDC{V,O} to be zero and add can_tdc_const::tdc{v,o,f}_min

2021-10-24T14:24:28+00:00

ISO 11898-1 specifies in section 11.3.3 "Transmitter delay
compensation" that "the configuration range for [the] SSP position
shall be at least 0 to 63 minimum time quanta."

Because SSP = TDCV + TDCO, it means that we should allow both TDCV and
TDCO to hold zero value in order to honor SSP's minimum possible
value.

However, current implementation assigned special meaning to TDCV and
TDCO's zero values:
  * TDCV = 0 -> TDCV is automatically measured by the transceiver.
  * TDCO = 0 -> TDC is off.

In order to allow for those values to really be zero and to maintain
current features, we introduce two new flags:
  * CAN_CTRLMODE_TDC_AUTO indicates that the controller support
    automatic measurement of TDCV.
  * CAN_CTRLMODE_TDC_MANUAL indicates that the controller support
    manual configuration of TDCV. N.B.: current implementation failed
    to provide an option for the driver to indicate that only manual
    mode was supported.

TDC is disabled if both CAN_CTRLMODE_TDC_AUTO and
CAN_CTRLMODE_TDC_MANUAL flags are off, c.f. the helper function
can_tdc_is_enabled() which is also introduced in this patch.

Also, this patch adds three fields: tdcv_min, tdco_min and tdcf_min to
struct can_tdc_const. While we are not convinced that those three
fields could be anything else than zero, we can imagine that some
controllers might specify a lower bound on these. Thus, those minimums
are really added "just in case".

Comments of struct can_tdc and can_tdc_const are updated accordingly.

Finally, the changes are applied to the etas_es58x driver.

Link: https://lore.kernel.org/all/20210918095637.20108-2-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde