linux.git/include/linux/can, branch v5.15.187

can: length: fix bitstuffing count

2023-07-23T11:46:54+00:00

[ Upstream commit 9fde4c557f78ee2f3626e92b4089ce9d54a2573a ]

The Stuff Bit Count is always coded on 4 bits [1]. Update the Stuff
Bit Count size accordingly.

In addition, the CRC fields of CAN FD Frames contain stuff bits at
fixed positions called fixed stuff bits [2]. The CRC field starts with
a fixed stuff bit and then has another fixed stuff bit after each
fourth bit [2], which allows us to derive this formula:

  FSB count = 1 + round_down(len(CRC field)/4)

The length of the CRC field is [1]:

  len(CRC field) = len(Stuff Bit Count) + len(CRC)
                 = 4 + len(CRC)

with len(CRC) either 17 or 21 bits depending of the payload length.

In conclusion, for CRC17:

  FSB count = 1 + round_down((4 + 17)/4)
            = 6

and for CRC 21:

  FSB count = 1 + round_down((4 + 21)/4)
            = 7

Add a Fixed Stuff bits (FSB) field with above values and update
CANFD_FRAME_OVERHEAD_SFF and CANFD_FRAME_OVERHEAD_EFF accordingly.

[1] ISO 11898-1:2015 section 10.4.2.6 "CRC field":

  The CRC field shall contain the CRC sequence followed by a recessive
  CRC delimiter. For FD Frames, the CRC field shall also contain the
  stuff count.

  Stuff count

  If FD Frames, the stuff count shall be at the beginning of the CRC
  field. It shall consist of the stuff bit count modulo 8 in a 3-bit
  gray code followed by a parity bit [...]

[2] ISO 11898-1:2015 paragraph 10.5 "Frame coding":

  In the CRC field of FD Frames, the stuff bits shall be inserted at
  fixed positions; they are called fixed stuff bits. There shall be a
  fixed stuff bit before the first bit of the stuff count, even if the
  last bits of the preceding field are a sequence of five consecutive
  bits of identical value, there shall be only the fixed stuff bit,
  there shall not be two consecutive stuff bits. A further fixed stuff
  bit shall be inserted after each fourth bit of the CRC field [...]

Fixes: 85d99c3e2a13 ("can: length: can_skb_get_frame_len(): introduce function to get data length of frame in data link layer")
Suggested-by: Thomas Kopp 
Signed-off-by: Vincent Mailhol 
Reviewed-by: Thomas Kopp 
Link: https://lore.kernel.org/all/20230611025728.450837-2-mailhol.vincent@wanadoo.fr
Signed-off-by: Marc Kleine-Budde 
Signed-off-by: Sasha Levin

can: sja1000: fix size of OCR_MODE_MASK define

2022-12-19T11:36:42+00:00

[ Upstream commit 26e8f6a75248247982458e8237b98c9fb2ffcf9d ]

bitfield mode in ocr register has only 2 bits not 3, so correct
the OCR_MODE_MASK define.

Signed-off-by: Heiko Schocher 
Link: https://lore.kernel.org/all/20221123071636.2407823-1-hs@denx.de
Signed-off-by: Marc Kleine-Budde 
Signed-off-by: Sasha Levin

can: dev: provide optional GPIO based termination support

2021-08-19T13:07:03+00:00

For CAN buses to work, a termination resistor has to be present at both
ends of the bus. This resistor is usually 120 Ohms, other values may be
required for special bus topologies.

This patch adds support for a generic GPIO based CAN termination. The
resistor value has to be specified via device tree, and it can only be
attached to or detached from the bus. By default the termination is not
active.

Link: https://lore.kernel.org/r/20210818071232.20585-4-o.rempel@pengutronix.de
Signed-off-by: Oleksij Rempel 
Signed-off-by: Marc Kleine-Budde

can: flexcan: add platform data header

2021-07-25T09:36:29+00:00

Add platform data header for flexcan.

Link: https://lore.kernel.org/r/20210702094841.327679-1-angelo@kernel-space.org
Signed-off-by: Angelo Dureghello 
Signed-off-by: Marc Kleine-Budde

can: bittiming: fix documentation for struct can_tdc

2021-07-25T09:36:25+00:00

This patch fixes a typo in the documentation for struct can_tdc::tdcv.
The number "0" refers to automatic mode not the letter "O".

Further two grammar errors in the documentation for struct can_tdc are
fixed.

First grammar error: add a missing third person 's'.

Second grammar error: replace "such as" by "such that". The intent is
to give a condition, not an example.

Fixes: 289ea9e4ae59 ("can: add new CAN FD bittiming parameters: Transmitter Delay Compensation (TDC)")
Link: https://lore.kernel.org/r/20210616095922.2430415-1-mkl@pengutronix.de
Link: https://lore.kernel.org/r/20210616124057.60723-1-mailhol.vincent@wanadoo.fr
Co-developed-by: Vincent Mailhol 
Signed-off-by: Vincent Mailhol 
Acked-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: rx-offload: can_rx_offload_threaded_irq_finish(): add new function to be called from threaded interrupt

2021-07-25T09:36:25+00:00

After reading all CAN frames from the controller in the IRQ handler
and storing them into a skb_queue, the driver calls napi_schedule().
In the napi poll function the skb from the skb_queue are then pushed
into the networking stack.

However if napi_schedule() is called from a threaded IRQ handler this
triggers the following error:

| NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!

To avoid this, create a new rx-offload
function (can_rx_offload_threaded_irq_finish()) with a call to
local_bh_disable()/local_bh_enable() around the napi_schedule() call.

Convert all drivers that call can_rx_offload_irq_finish() from
threaded IRQ context to can_rx_offload_threaded_irq_finish().

Link: https://lore.kernel.org/r/20210724204745.736053-4-mkl@pengutronix.de
Suggested-by: Daniel Glöckner 
Tested-by: Oleksij Rempel 
Signed-off-by: Marc Kleine-Budde

can: rx-offload: can_rx_offload_irq_finish(): directly call napi_schedule()

2021-07-25T09:36:25+00:00

Instead of calling can_rx_offload_schedule() call napi_schedule()
directly. As this was the last use of can_rx_offload_schedule() remove
this helper function.

Link: https://lore.kernel.org/r/20210724204745.736053-3-mkl@pengutronix.de
Tested-by: Oleksij Rempel 
Signed-off-by: Marc Kleine-Budde

can: rx-offload: add skb queue for use during ISR

2021-07-25T09:36:25+00:00

Adding a skb to the skb_queue in rx-offload requires to take a lock.

This commit avoids this by adding an unlocked skb queue that is
appended at the end of the ISR. Having one lock at the end of the ISR
should be OK as the HW is empty, not about to overflow.

Link: https://lore.kernel.org/r/20210724204745.736053-2-mkl@pengutronix.de
Tested-by: Oleksij Rempel 
Co-developed-by: Kurt Van Dijck 
Signed-off-by: Kurt Van Dijck 
Signed-off-by: Marc Kleine-Budde

can: bittiming: add CAN_KBPS, CAN_MBPS and CAN_MHZ macros

2021-03-30T09:14:45+00:00

Add three macro to simplify the readability of big bit timing numbers:
  - CAN_KBPS: kilobits per second (one thousand)
  - CAN_MBPS: megabits per second (one million)
  - CAN_MHZ: megahertz per second (one million)

Example:
	u32 bitrate_max = 8 * CAN_MBPS;
	struct can_clock clock = {.freq = 80 * CAN_MHZ};
instead of:
	u32 bitrate_max = 8000000;
	struct can_clock clock = {.freq = 80000000};

Apply the new macro to driver/net/can/dev/bittiming.c.

Link: https://lore.kernel.org/r/20210306054040.76483-1-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde

can: bittiming: add calculation for CAN FD Transmitter Delay Compensation (TDC)

2021-03-30T09:14:45+00:00

The logic for the tdco calculation is to just reuse the normal sample
point: tdco = sp. Because the sample point is expressed in tenth of
percent and the tdco is expressed in time quanta, a conversion is
needed.

At the end,
     ssp = tdcv + tdco
         = tdcv + sp.

Another popular method is to set tdco to the middle of the bit:
     tdc->tdco = can_bit_time(dbt) / 2
During benchmark tests, we could not find a clear advantages for one
of the two methods.

The tdco calculation is triggered each time the data_bittiming is
changed so that users relying on automated calculation can use the
netlink interface the exact same way without need of new parameters.
For example, a command such as:
	ip link set canX type can bitrate 500000 dbitrate 4000000 fd on
would trigger the calculation.

The user using CONFIG_CAN_CALC_BITTIMING who does not want automated
calculation needs to manually set tdco to zero.
For example with:
	ip link set canX type can tdco 0 bitrate 500000 dbitrate 4000000 fd on
(if the tdco parameter is provided in a previous command, it will be
overwritten).

If tdcv is set to zero (default), it is automatically calculated by
the transiver for each frame. As such, there is no code in the kernel
to calculate it.

tdcf has no automated calculation functions because we could not
figure out a formula for this parameter.

Link: https://lore.kernel.org/r/20210224002008.4158-6-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol 
Signed-off-by: Marc Kleine-Budde