[ Upstream commit 3e82f2f34c930a2a0a9e69fdc2de2f2f1388b442 ]
During frame reception while the MCAN is in Error Passive state and the Receive Error Counter has thevalue MCAN_ECR.REC = 127, it may happen that MCAN_IR.MRAF is set although there was no Message RAM access failure. If MCAN_IR.MRAF is enabled, an interrupt to the Host CPU is generated.
Work around: The Message RAM Access Failure interrupt routine needs to check whether
MCAN_ECR.RP = '1' and MCAN_ECR.REC = '127'.
In this case, reset MCAN_IR.MRAF. No further action is required. This affects versions older than 3.2.0
Errata explained on Sama5d2 SoC which includes this hardware block: http://ww1.microchip.com/downloads/en/DeviceDoc/SAMA5D2-Family-Silicon-Errat... chapter 6.2
Reproducibility: If 2 devices with m_can are connected back to back, configuring different bitrate on them will lead to interrupt storm on the receiving side, with error "Message RAM access failure occurred". Another way is to have a bad hardware connection. Bad wire connection can lead to this issue as well.
This patch fixes the issue according to provided workaround.
Signed-off-by: Eugen Hristev eugen.hristev@microchip.com Reviewed-by: Ludovic Desroches ludovic.desroches@microchip.com Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/can/m_can/m_can.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c index d3ce904e929e..ebad93ac8f11 100644 --- a/drivers/net/can/m_can/m_can.c +++ b/drivers/net/can/m_can/m_can.c @@ -818,6 +818,27 @@ static int m_can_poll(struct napi_struct *napi, int quota) if (!irqstatus) goto end;
+ /* Errata workaround for issue "Needless activation of MRAF irq" + * During frame reception while the MCAN is in Error Passive state + * and the Receive Error Counter has the value MCAN_ECR.REC = 127, + * it may happen that MCAN_IR.MRAF is set although there was no + * Message RAM access failure. + * If MCAN_IR.MRAF is enabled, an interrupt to the Host CPU is generated + * The Message RAM Access Failure interrupt routine needs to check + * whether MCAN_ECR.RP = ’1’ and MCAN_ECR.REC = 127. + * In this case, reset MCAN_IR.MRAF. No further action is required. + */ + if ((priv->version <= 31) && (irqstatus & IR_MRAF) && + (m_can_read(priv, M_CAN_ECR) & ECR_RP)) { + struct can_berr_counter bec; + + __m_can_get_berr_counter(dev, &bec); + if (bec.rxerr == 127) { + m_can_write(priv, M_CAN_IR, IR_MRAF); + irqstatus &= ~IR_MRAF; + } + } + psr = m_can_read(priv, M_CAN_PSR); if (irqstatus & IR_ERR_STATE) work_done += m_can_handle_state_errors(dev, psr);