[PATCH net-next 13/37] can: rcar_canfd: Do not set registers selecting the CAN mode

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

From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>

The bits 30 (classical CAN-only mode) and 28 (FD-only enable) of the
Channel n CAN-FD Configuration Register of the Renesas RZ/G3S SoC are not
available. The IP supports only CAN-FD mode. RZ/G3S HW manual (revision
1.30) specify the bits are read as zero and the write value should always
be zero.

Add the mode_select_na flag in struct rcar_canfd_hw_info to cover RZ/G3S
and avoid writing to unavailable bits.

The existing struct rcar_canfd_hw_info instances were updated to address
the request in the Link discussion.

Commit prepares for the addition of the Renesas RZ/G3S SoC.

Link: https://lore.kernel.org/all/1d9719e3-10ff-4cd8-b729-55fea93c37ce@wanadoo.fr
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://patch.msgid.link/20260902141544.565763-5-claudiu.beznea+renesas@tuxon.dev
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/rcar/rcar_canfd.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c
index f9173774387f..ac5d5959d8e4 100644
--- a/drivers/net/can/rcar/rcar_canfd.c
+++ b/drivers/net/can/rcar/rcar_canfd.c
@@ -445,6 +445,7 @@ struct rcar_canfd_hw_info {
 	unsigned shared_can_regs:1;	/* Has shared classical can registers */
 	unsigned external_clk:1;	/* Has external clock */
 	unsigned fcan_pclk:1;		/* Has fcan sourced from pclk. */
+	unsigned fixed_canfd:1;		/* Has mode fixed to canfd. */
 };
 
 /* Channel priv data */
@@ -619,6 +620,7 @@ static const struct rcar_canfd_hw_info rcar_gen3_hw_info = {
 	.shared_can_regs = 0,
 	.external_clk = 1,
 	.fcan_pclk = 0,
+	.fixed_canfd = 0,
 };
 
 static const struct rcar_canfd_hw_info rcar_gen4_hw_info = {
@@ -637,6 +639,7 @@ static const struct rcar_canfd_hw_info rcar_gen4_hw_info = {
 	.shared_can_regs = 1,
 	.external_clk = 1,
 	.fcan_pclk = 0,
+	.fixed_canfd = 0,
 };
 
 static const struct rcar_canfd_hw_info rzg2l_hw_info = {
@@ -655,6 +658,7 @@ static const struct rcar_canfd_hw_info rzg2l_hw_info = {
 	.shared_can_regs = 0,
 	.external_clk = 1,
 	.fcan_pclk = 0,
+	.fixed_canfd = 0,
 };
 
 static const struct rcar_canfd_hw_info r9a09g047_hw_info = {
@@ -673,6 +677,7 @@ static const struct rcar_canfd_hw_info r9a09g047_hw_info = {
 	.shared_can_regs = 1,
 	.external_clk = 0,
 	.fcan_pclk = 0,
+	.fixed_canfd = 0,
 };
 
 static const struct rcar_canfd_hw_info r9a09g077_hw_info = {
@@ -691,6 +696,7 @@ static const struct rcar_canfd_hw_info r9a09g077_hw_info = {
 	.shared_can_regs = 1,
 	.external_clk = 1,
 	.fcan_pclk = 0,
+	.fixed_canfd = 0,
 };
 
 /* Helper functions */
@@ -846,6 +852,9 @@ static int rcar_canfd_reset_controller(struct rcar_canfd_global *gpriv)
 		}
 
 		/* Set the controller into appropriate mode */
+		if (gpriv->info->fixed_canfd)
+			continue;
+
 		if (gpriv->info->ch_interface_mode) {
 			/* Do not set CLOE and FDOE simultaneously */
 			if (!gpriv->fdmode) {
-- 
2.53.0