net: dsa: sja1105: allow RX timestamps to be taken on all ports for SJA1110

On SJA1105, there is support for a cascade port which is presumably
connected to a downstream SJA1105 switch. The upstream one does not take
PTP timestamps for packets received on this port, presumably because the
downstream switch already did (and for PTP, it only makes sense for the
leaf nodes in a DSA switch tree to do that).

I haven't been able to validate that feature in a fully assembled setup,
so I am disabling the feature by setting the cascade port to an unused
port value (ds->num_ports).

In SJA1110, multiple cascade ports are supported, and CASC_PORT became
a bit mask from a port number. So when CASC_PORT is set to ds->num_ports
(which is 11 on SJA1110), it is actually set to 0b1011, so ports 3, 1
and 0 are configured as cascade ports and we cannot take RX timestamps
on them.

So we need to introduce a check for SJA1110 and set things differently
(to zero there), so that the cascading feature is properly disabled and
RX timestamps can be taken on all ports.

Signed-off-by: Vladimir Oltean <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/dsa/sja1105/sja1105.h

···
 	int num_cbs_shapers;
 	int max_frame_mem;
 	int num_ports;
+	bool multiple_cascade_ports;
 	const struct sja1105_dynamic_table_ops *dyn_ops;
 	const struct sja1105_table_ops *static_ops;
 	const struct sja1105_regs *regs;

drivers/net/dsa/sja1105/sja1105_main.c

···
 		.host_port = priv->ds->num_ports,
 		/* Default to an invalid value */
 		.mirr_port = priv->ds->num_ports,
-		/* Link-local traffic received on casc_port will be forwarded
-		 * to host_port without embedding the source port and device ID
-		 * info in the destination MAC address (presumably because it
-		 * is a cascaded port and a downstream SJA switch already did
-		 * that). Default to an invalid port (to disable the feature)
-		 * and overwrite this if we find any DSA (cascaded) ports.
-		 */
-		.casc_port = priv->ds->num_ports,
 		/* No TTEthernet */
 		.vllupformat = SJA1105_VL_FORMAT_PSFP,
 		.vlmarker = 0,
···
 		/* Enable the TTEthernet engine on SJA1110 */
 		.tte_en = true,
 	};
+	struct sja1105_general_params_entry *general_params;
 	struct dsa_switch *ds = priv->ds;
 	struct sja1105_table *table;
 	int port;
···
 
 	table->entry_count = table->ops->max_entry_count;
 
+	general_params = table->entries;
+
 	/* This table only has a single entry */
-	((struct sja1105_general_params_entry *)table->entries)[0] =
-				default_general_params;
+	general_params[0] = default_general_params;
 
 	sja1110_select_tdmaconfigidx(priv);
+
+	/* Link-local traffic received on casc_port will be forwarded
+	 * to host_port without embedding the source port and device ID
+	 * info in the destination MAC address, and no RX timestamps will be
+	 * taken either (presumably because it is a cascaded port and a
+	 * downstream SJA switch already did that).
+	 * To disable the feature, we need to do different things depending on
+	 * switch generation. On SJA1105 we need to set an invalid port, while
+	 * on SJA1110 which support multiple cascaded ports, this field is a
+	 * bitmask so it must be left zero.
+	 */
+	if (!priv->info->multiple_cascade_ports)
+		general_params->casc_port = ds->num_ports;
 
 	return 0;
 }

drivers/net/dsa/sja1105/sja1105_spi.c

···
 	.regs			= &sja1110_regs,
 	.qinq_tpid		= ETH_P_8021AD,
 	.can_limit_mcast_flood	= true,
+	.multiple_cascade_ports	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,
···
 	.regs			= &sja1110_regs,
 	.qinq_tpid		= ETH_P_8021AD,
 	.can_limit_mcast_flood	= true,
+	.multiple_cascade_ports	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,
···
 	.regs			= &sja1110_regs,
 	.qinq_tpid		= ETH_P_8021AD,
 	.can_limit_mcast_flood	= true,
+	.multiple_cascade_ports	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,
···
 	.regs			= &sja1110_regs,
 	.qinq_tpid		= ETH_P_8021AD,
 	.can_limit_mcast_flood	= true,
+	.multiple_cascade_ports	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,