From: Fedor Ross <fedor.ross@xxxxxxx>
The mcp251xfd controller needs an idle bus to enter 'Normal CAN 2.0
mode' or . The maximum length of a CAN frame is 736 bits (64 data
bytes, CAN-FD, EFF mode, worst case bit stuffing and interframe
spacing). For low bit rates like 10 kbit/s the arbitrarily chosen
MCP251XFD_POLL_TIMEOUT_US of 1 ms is too small.
Otherwise during polling for the CAN controller to enter 'Normal CAN
2.0 mode' the timeout limit is exceeded and the configuration fails
with:
| $ ip link set dev can1 up type can bitrate 10000
| [ 731.911072] mcp251xfd spi2.1 can1: Controller failed to enter mode CAN 2.0 Mode (6) and stays in Configuration Mode (4) (con=0x068b0760, osc=0x00000468).
| [ 731.927192] mcp251xfd spi2.1 can1: CRC read error at address 0x0e0c (length=4, data=00 00 00 00, CRC=0x0000) retrying.
| [ 731.938101] A link change request failed with some changes committed already. Interface can1 may have been left with an inconsistent configuration, please check.
| RTNETLINK answers: Connection timed out
Make MCP251XFD_POLL_TIMEOUT_US timeout calculation dynamic. Use
maximum of 1ms and bit time of 1 full 64 data bytes CAN-FD frame in
EFF mode, worst case bit stuffing and interframe spacing at the
current bit rate.
For easier backporting define the macro MCP251XFD_FRAME_LEN_MAX_BITS
that holds the max frame length in bits, which is 736. This can be
replaced by can_frame_bits(true, true, true, true, CANFD_MAX_DLEN) in
a cleanup patch later.
Fixes: 55e5b97f003e8 ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Signed-off-by: Fedor Ross <fedor.ross@xxxxxxx>
Signed-off-by: Marek Vasut <marex@xxxxxxx>
Cc: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
Cc: Manivannan Sadhasivam <mani@xxxxxxxxxx>
Cc: Thomas Kopp <thomas.kopp@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
Hello,
picking up Fedor's and Marek's work. I decided to make it a minimal
patch and add stable on Cc. The mentioned cleanup patch that replaces
736 by can_frame_bits() can be done later and will go upstream via
can-next.
regards,
Marc
v3:
- use 736 as max CAN frame length, calculated by Vincent Mailhol's
80a2fbce456e ("can: length: refactor frame lengths definition to add size in bits")
- update commit message
- drop patch 2/2
v2: https://lore.kernel.org/all/20230505222820.126441-1-marex@xxxxxxx
- Add macros for CAN_BIT_STUFFING_OVERHEAD and CAN_IDLE_CONDITION_SAMPLES
(thanks Thomas, but please double check the comments)
- Update commit message
v1: https://lore.kernel.org/all/20230504195059.4706-1-marex@xxxxxxx
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c | 4 +++-
drivers/net/can/spi/mcp251xfd/mcp251xfd.h | 1 +
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index 68df6d4641b5..876e8e3cbb0b 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -227,6 +227,7 @@ static int
__mcp251xfd_chip_set_mode(const struct mcp251xfd_priv *priv,
const u8 mode_req, bool nowait)
{
+ const struct can_bittiming *bt = &priv->can.bittiming;
u32 con = 0, con_reqop, osc = 0;
u8 mode;
int err;
@@ -251,7 +252,8 @@ __mcp251xfd_chip_set_mode(const struct mcp251xfd_priv *priv,
FIELD_GET(MCP251XFD_REG_CON_OPMOD_MASK,
con) == mode_req,
MCP251XFD_POLL_SLEEP_US,
- MCP251XFD_POLL_TIMEOUT_US);
+ max_t(unsigned long, MCP251XFD_POLL_TIMEOUT_US,
+ MCP251XFD_FRAME_LEN_MAX_BITS * USEC_PER_SEC / bt->bitrate));
if (err != -ETIMEDOUT && err != -EBADMSG)
return err;
diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
index 7024ff0cc2c0..24510b3b8020 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
@@ -387,6 +387,7 @@ static_assert(MCP251XFD_TIMESTAMP_WORK_DELAY_SEC <
#define MCP251XFD_OSC_STAB_TIMEOUT_US (10 * MCP251XFD_OSC_STAB_SLEEP_US)
#define MCP251XFD_POLL_SLEEP_US (10)
#define MCP251XFD_POLL_TIMEOUT_US (USEC_PER_MSEC)
+#define MCP251XFD_FRAME_LEN_MAX_BITS (736)
/* Misc */
#define MCP251XFD_NAPI_WEIGHT 32
--
2.40.1
