can: rockchip_canfd: implement workaround for erratum 12

The rk3568 CAN-FD errata sheet as of Tue 07 Nov 2023 11:25:31 +08:00
says:

| A dominant bit at the third bit of the intermission may cause a
| transmission error.
|
| When sampling the third bit of the intermission as a dominant bit, if
| tx_req is configured to transmit extended frames at this time, the
| extended frame may be sent to the bus in the format of a standard
| frame. The extended frame will be sent as a standard frame and will not
| result in error frames

Turn on "Interframe Spaceing RX Mode" only during TX to work around
erratum 12, according to rock-chip:

| Spaceing RX Mode = 1, the third Bit between frames cannot receive
| and send, and the fourth Bit begins to receive and send.
|
| Spaceing RX Mode = 0, allowing the third Bit between frames to
| receive and send.

Message-ID: <be72939f-0a9e-0608-dfff-7b0096a26eba@rock-chips.com>
Tested-by: Alibek Omarov <a1ba.omarov@gmail.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20240904-rockchip-canfd-v5-13-8ae22bcb27cc@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/rockchip/rockchip_canfd-tx.c

@@ -11,7 +11,14 @@
 static void rkcanfd_start_xmit_write_cmd(const struct rkcanfd_priv *priv,
 					 const u32 reg_cmd)
 {
+	if (priv->devtype_data.quirks & RKCANFD_QUIRK_RK3568_ERRATUM_12)
+		rkcanfd_write(priv, RKCANFD_REG_MODE, priv->reg_mode_default |
+			      RKCANFD_REG_MODE_SPACE_RX_MODE);
+
 	rkcanfd_write(priv, RKCANFD_REG_CMD, reg_cmd);
+
+	if (priv->devtype_data.quirks & RKCANFD_QUIRK_RK3568_ERRATUM_12)
+		rkcanfd_write(priv, RKCANFD_REG_MODE, priv->reg_mode_default);
 }
 
 void rkcanfd_xmit_retry(struct rkcanfd_priv *priv)