In 2b9aecdce2 ("can: c_can: Disable rx split as workaround") a new Kconfig
option was introduced as a workaround. The tests performed by Alexander Stein
confirmed this option to be obsolete with all the other cleanups and fixes
that had been discussed that time:
http://marc.info/?l=linux-can&m=139746476821294&w=2
Both (author and tester) agreed to remove this Kconfig option again:
http://marc.info/?l=linux-can&m=139883820714229&w=2
As some more cleanups took place since then a simple revert is not possible.
This patch removes the entire option as it would behave when disabled.
Further beautification’s can be done later.
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
The RX buffer split causes packet loss in the hardware:
What happens is:
RX Packet 1 --> message buffer 1 (newdat bit is not cleared)
RX Packet 2 --> message buffer 2 (newdat bit is not cleared)
RX Packet 3 --> message buffer 3 (newdat bit is not cleared)
RX Packet 4 --> message buffer 4 (newdat bit is not cleared)
RX Packet 5 --> message buffer 5 (newdat bit is not cleared)
RX Packet 6 --> message buffer 6 (newdat bit is not cleared)
RX Packet 7 --> message buffer 7 (newdat bit is not cleared)
RX Packet 8 --> message buffer 8 (newdat bit is not cleared)
Clear newdat bit in message buffer 1
Clear newdat bit in message buffer 2
Clear newdat bit in message buffer 3
Clear newdat bit in message buffer 4
Clear newdat bit in message buffer 5
Clear newdat bit in message buffer 6
Clear newdat bit in message buffer 7
Clear newdat bit in message buffer 8
Now if during that clearing of newdat bits, a new message comes in,
the HW gets confused and drops it.
It does not matter how many of them you clear. I put a delay between
clear of buffer 1 and buffer 2 which was long enough that the message
should have been queued either in buffer 1 or buffer 9. But it did not
show up anywhere. The next message ended up in buffer 1. So the
hardware lost a packet of course without telling it via one of the
error handlers.
That does not happen on all clear newdat bit events. I see one of 10k
packets dropped in the scenario which allows us to reproduce. But the
trace looks always the same.
Not splitting the RX Buffer avoids the packet loss but can cause
reordering. It's hard to trigger, but it CAN happen.
With that mode we use the HW as it was probably designed for. We read
from the buffer 1 upwards and clear the buffer as we get the
message. That's how all microcontrollers use it. So I assume that the
way we handle the buffers was never really tested. According to the
public documentation it should just work :)
Let the user decide which evil is the lesser one.
[ Oliver Hartkopp: Provided a sane config option and help text and
made me switch to favour potential and unlikely reordering over
packet loss ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This patch adds an 'if CAN_DEV...endif' Block around the CAN driver
symbols in drivers/net/can/Kconfig. So the 'depends on CAN' dependencies
can be removed.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This patch adds the support for D_CAN controller driver to the existing
C_CAN driver.
Bosch D_CAN controller is a full-CAN implementation which is compliant
to CAN protocol version 2.0 part A and B. Bosch D_CAN user manual can be
obtained from: http://www.semiconductors.bosch.de/media/en/pdf/
ipmodules_1/can/d_can_users_manual_111.pdf
A new array is added for accessing the d_can registers, according to d_can
controller register space.
Current D_CAN implementation has following limitations, this is done
to avoid large changes to the C_CAN driver.
1. Message objects are limited to 32, 16 for RX and 16 for TX. C_CAN IP
supports upto 32 message objects but in case of D_CAN we can configure
upto 128 message objects.
2. Using two 16bit reads/writes for accessing the 32bit D_CAN registers.
3. These patches have been tested on little endian machine, there might
be some hidden endian-related issues due to the nature of the accesses
(32-bit registers accessed as 2 16-bit registers). However, I do not
have a big-endian D_CAN implementation to confirm.
Signed-off-by: AnilKumar Ch <anilkumar@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Bosch C_CAN controller is a full-CAN implementation which is compliant
to CAN protocol version 2.0 part A and B. Bosch C_CAN user manual can be
obtained from:
http://www.semiconductors.bosch.de/media/en/pdf/ipmodules_1/c_can/users_manual_c_can.pdf
This patch adds the support for this controller.
The following are the design choices made while writing the controller
driver:
1. Interface Register set IF1 has be used only in the current design.
2. Out of the 32 Message objects available, 16 are kept aside for RX
purposes and the rest for TX purposes.
3. NAPI implementation is such that both the TX and RX paths function
in polling mode.
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Oliver Hartkopp