[PATCH can-next 15/21] can: rockchip_canfd: rkcanfd_get_berr_counter_corrected(): work around broken {RX,TX}ERRORCNT register

[Marc Kleine-Budde <mkl@pengutronix.de>]

Tests show that sometimes both CAN bus error counters read 0x0, even
if the controller is in warning mode
(RKCANFD_REG_STATE_ERROR_WARNING_STATE in RKCANFD_REG_STATE
set).

To work around this issue, if both error counters read from hardware
are 0x0, use the structure priv->bec, otherwise save the read value in
priv->bec.

In rkcanfd_handle_rx_int_one() decrement the priv->bec.rxerr for
successfully RX'ed CAN frames.

In rkcanfd_handle_tx_done_one() decrement the priv->bec.txerr for
successfully TX'ed CAN frames.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/rockchip/rockchip_canfd-core.c | 47 ++++++++++++++++++++++----
 drivers/net/can/rockchip/rockchip_canfd-rx.c   | 15 ++++++++
 drivers/net/can/rockchip/rockchip_canfd-tx.c   |  8 +++++
 drivers/net/can/rockchip/rockchip_canfd.h      |  2 ++
 4 files changed, 66 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/rockchip/rockchip_canfd-core.c b/drivers/net/can/rockchip/rockchip_canfd-core.c
index 03ad7936034b..5d78ec8dba7e 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-core.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-core.c
@@ -159,14 +159,47 @@ static int rkcanfd_set_bittiming(struct rkcanfd_priv *priv)
 	return 0;
 }
 
-static void rkcanfd_get_berr_counter_raw(struct rkcanfd_priv *priv,
-					 struct can_berr_counter *bec)
+static void rkcanfd_get_berr_counter_corrected(struct rkcanfd_priv *priv,
+					       struct can_berr_counter *bec)
 {
 	struct can_berr_counter bec_raw;
+	u32 reg_state;
 
 	bec->rxerr = rkcanfd_read(priv, RKCANFD_REG_RXERRORCNT);
 	bec->txerr = rkcanfd_read(priv, RKCANFD_REG_TXERRORCNT);
 	bec_raw = *bec;
+
+	/* Tests show that sometimes both CAN bus error counters read
+	 * 0x0, even if the controller is in warning mode
+	 * (RKCANFD_REG_STATE_ERROR_WARNING_STATE in RKCANFD_REG_STATE
+	 * set).
+	 *
+	 * In case both error counters read 0x0, use the struct
+	 * priv->bec, otherwise save the read value to priv->bec.
+	 *
+	 * rkcanfd_handle_rx_int_one() handles the decrementing of
+	 * priv->bec.rxerr for successfully RX'ed CAN frames.
+	 *
+	 * Luckily the controller doesn't decrement the RX CAN bus
+	 * error counter in hardware for self received TX'ed CAN
+	 * frames (RKCANFD_REG_MODE_RXSTX_MODE), so RXSTX doesn't
+	 * interfere with proper RX CAN bus error counters.
+	 *
+	 * rkcanfd_handle_tx_done_one() handles the decrementing of
+	 * priv->bec.txerr for successfully TX'ed CAN frames.
+	 */
+	if (!bec->rxerr && !bec->txerr)
+		*bec = priv->bec;
+	else
+		priv->bec = *bec;
+
+	reg_state = rkcanfd_read(priv, RKCANFD_REG_STATE);
+	netdev_vdbg(priv->ndev,
+		    "%s: Raw/Cor: txerr=%3u/%3u rxerr=%3u/%3u Bus Off=%u Warning=%u\n",
+		    __func__,
+		    bec_raw.txerr, bec->txerr, bec_raw.rxerr, bec->rxerr,
+		    !!(reg_state & RKCANFD_REG_STATE_BUS_OFF_STATE),
+		    !!(reg_state & RKCANFD_REG_STATE_ERROR_WARNING_STATE));
 }
 
 static int rkcanfd_get_berr_counter(const struct net_device *ndev,
@@ -179,7 +212,7 @@ static int rkcanfd_get_berr_counter(const struct net_device *ndev,
 	if (err)
 		return err;
 
-	rkcanfd_get_berr_counter_raw(priv, bec);
+	rkcanfd_get_berr_counter_corrected(priv, bec);
 
 	pm_runtime_put(ndev->dev.parent);
 
@@ -255,6 +288,8 @@ static void rkcanfd_chip_start(struct rkcanfd_priv *priv)
 		RKCANFD_REG_INT_OVERLOAD_INT |
 		RKCANFD_REG_INT_TX_FINISH_INT;
 
+	memset(&priv->bec, 0x0, sizeof(priv->bec));
+
 	rkcanfd_chip_fifo_setup(priv);
 	rkcanfd_timestamp_init(priv);
 	rkcanfd_set_bittiming(priv);
@@ -491,7 +526,7 @@ static int rkcanfd_handle_error_int(struct rkcanfd_priv *priv)
 	if (cf) {
 		struct can_berr_counter bec;
 
-		rkcanfd_get_berr_counter_raw(priv, &bec);
+		rkcanfd_get_berr_counter_corrected(priv, &bec);
 		cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR | CAN_ERR_CNT;
 		cf->data[6] = bec.txerr;
 		cf->data[7] = bec.rxerr;
@@ -520,7 +555,7 @@ static int rkcanfd_handle_state_error_int(struct rkcanfd_priv *priv)
 	u32 timestamp;
 	int err;
 
-	rkcanfd_get_berr_counter_raw(priv, &bec);
+	rkcanfd_get_berr_counter_corrected(priv, &bec);
 	can_state_get_by_berr_counter(ndev, &bec, &tx_state, &rx_state);
 
 	new_state = max(tx_state, rx_state);
@@ -573,7 +608,7 @@ rkcanfd_handle_rx_fifo_overflow_int(struct rkcanfd_priv *priv)
 	if (skb)
 		return 0;
 
-	rkcanfd_get_berr_counter_raw(priv, &bec);
+	rkcanfd_get_berr_counter_corrected(priv, &bec);
 
 	cf->can_id |= CAN_ERR_CRTL | CAN_ERR_CNT;
 	cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
diff --git a/drivers/net/can/rockchip/rockchip_canfd-rx.c b/drivers/net/can/rockchip/rockchip_canfd-rx.c
index 15d52abad3b3..de647eed02df 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-rx.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-rx.c
@@ -167,6 +167,13 @@ static int rkcanfd_rxstx_filter(struct rkcanfd_priv *priv,
 
 	/* Affected by Erratum 6 */
 
+	/* Manual handling of CAN Bus Error counters. See
+	 * rkcanfd_get_corrected_berr_counter() for detailed
+	 * explanation.
+	 */
+	if (priv->bec.txerr)
+		priv->bec.txerr--;
+
 	*tx_done = true;
 
 	stats->tx_packets++;
@@ -229,6 +236,14 @@ static int rkcanfd_handle_rx_int_one(struct rkcanfd_priv *priv)
 			return 0;
 	}
 
+	/* Manual handling of CAN Bus Error counters. See
+	 * rkcanfd_get_corrected_berr_counter() for detailed
+	 * explanation.
+	 */
+	if (priv->bec.rxerr)
+		priv->bec.rxerr = min(CAN_ERROR_PASSIVE_THRESHOLD,
+				      priv->bec.rxerr) - 1;
+
 	if (header->frameinfo & RKCANFD_REG_FD_FRAMEINFO_FDF)
 		skb = alloc_canfd_skb(priv->ndev, &skb_cfd);
 	else
diff --git a/drivers/net/can/rockchip/rockchip_canfd-tx.c b/drivers/net/can/rockchip/rockchip_canfd-tx.c
index 43d011ab6455..d604994755d3 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-tx.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-tx.c
@@ -115,6 +115,14 @@ void rkcanfd_handle_tx_done_one(struct rkcanfd_priv *priv, const u32 ts,
 
 	tx_tail = rkcanfd_get_tx_tail(priv);
 	skb = priv->can.echo_skb[tx_tail];
+
+	/* Manual handling of CAN Bus Error counters. See
+	 * rkcanfd_get_corrected_berr_counter() for detailed
+	 * explanation.
+	 */
+	if (priv->bec.txerr)
+		priv->bec.txerr--;
+
 	stats->tx_bytes +=
 		can_rx_offload_get_echo_skb_queue_timestamp(&priv->offload,
 							    tx_tail, ts,
diff --git a/drivers/net/can/rockchip/rockchip_canfd.h b/drivers/net/can/rockchip/rockchip_canfd.h
index de6c72b3d235..e10797981b4d 100644
--- a/drivers/net/can/rockchip/rockchip_canfd.h
+++ b/drivers/net/can/rockchip/rockchip_canfd.h
@@ -458,6 +458,8 @@ struct rkcanfd_priv {
 	u32 reg_int_mask_default;
 	struct rkcanfd_devtype_data devtype_data;
 
+	struct can_berr_counter bec;
+
 	struct reset_control *reset;
 	struct clk_bulk_data *clks;
 	int clks_num;

-- 
2.43.0