phy: cadence-torrent: add support for three or more links using 2 protocols

The Torrent SERDES can support at most two different protocols (PHY types).
This only mandates that the device-tree sub-nodes used to represent the
configuration should describe links with at-most two different protocols.

The existing implementation however imposes an artificial constraint that
allows only two links (device-tree sub-nodes). As long as at-most two
protocols are chosen, using more than two links to describe them in an
alternating configuration is still a valid configuration of the Torrent
SERDES.

A 3-Link 2-Protocol configuration of the 4-Lane SERDES can be:
Lane 0 => Protocol 1 => Link 1
Lane 1 => Protocol 1 => Link 1
Lane 2 => Protocol 2 => Link 2
Lane 3 => Protocol 1 => Link 3

A 4-Link 2-Protocol configuration of the 4-Lane SERDES can be:
Lane 0 => Protocol 1 => Link 1
Lane 1 => Protocol 2 => Link 2
Lane 2 => Protocol 1 => Link 3
Lane 3 => Protocol 2 => Link 4
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/20240805092607.143869-1-s-vadapalli@ti.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/cadence/phy-cadence-torrent.c

@@ -351,6 +351,7 @@ struct cdns_torrent_phy {
 	void __iomem *sd_base; /* SD0801 registers base */
 	u32 max_bit_rate; /* Maximum link bit rate to use (in Mbps) */
 	u32 dp_pll;
+	u32 protocol_bitmask;
 	struct reset_control *phy_rst;
 	struct reset_control *apb_rst;
 	struct device *dev;
@@ -2473,32 +2474,80 @@ int cdns_torrent_phy_configure_multilink(struct cdns_torrent_phy *cdns_phy)
 	enum cdns_torrent_phy_type phy_t1, phy_t2;
 	const struct cdns_reg_pairs *reg_pairs;
 	int i, j, node, mlane, num_lanes, ret;
+	struct device *dev = cdns_phy->dev;
 	enum cdns_torrent_ssc_mode ssc;
 	struct regmap *regmap;
-	u32 num_regs;
+	u32 num_regs, num_protocols, protocol;
 
-	/* Maximum 2 links (subnodes) are supported */
-	if (cdns_phy->nsubnodes != 2)
+	num_protocols = hweight32(cdns_phy->protocol_bitmask);
+	/* Maximum 2 protocols are supported */
+	if (num_protocols > 2) {
+		dev_err(dev, "at most 2 protocols are supported\n");
 		return -EINVAL;
+	}
+
 
+	/**
+	 * Get PHY types directly from subnodes if only 2 subnodes exist.
+	 * It is possible for phy_t1 to be the same as phy_t2 for special
+	 * configurations such as PCIe Multilink.
+	 */
+	if (cdns_phy->nsubnodes == 2) {
 		phy_t1 = cdns_phy->phys[0].phy_type;
 		phy_t2 = cdns_phy->phys[1].phy_type;
+	} else {
+		/**
+		 * Both PHY types / protocols should be unique.
+		 * If they are the same, it should be expressed with either
+		 * a) Single-Link (1 Sub-node) - handled via PHY APIs
+		 * OR
+		 * b) Double-Link (2 Sub-nodes) - handled above
+		 */
+		if (num_protocols != 2) {
+			dev_err(dev, "incorrect representation of link\n");
+			return -EINVAL;
+		}
+
+		phy_t1 = fns(cdns_phy->protocol_bitmask, 0);
+		phy_t2 = fns(cdns_phy->protocol_bitmask, 1);
+	}
 
 	/**
-	 * First configure the PHY for first link with phy_t1. Get the array
-	 * values as [phy_t1][phy_t2][ssc].
+	 * Configure all links with the protocol phy_t1 first followed by
+	 * configuring all links with the protocol phy_t2.
+	 *
+	 * When phy_t1 = phy_t2, it is a single protocol and configuration
+	 * is performed with a single iteration of the protocol and multiple
+	 * iterations over the sub-nodes (links).
+	 *
+	 * When phy_t1 != phy_t2, there are two protocols and configuration
+	 * is performed by iterating over all sub-nodes matching the first
+	 * protocol and configuring them first, followed by iterating over
+	 * all sub-nodes matching the second protocol and configuring them
+	 * next.
 	 */
-	for (node = 0; node < cdns_phy->nsubnodes; node++) {
-		if (node == 1) {
+	for (protocol = 0; protocol < num_protocols; protocol++) {
 		/**
-			 * If first link with phy_t1 is configured, then
-			 * configure the PHY for second link with phy_t2.
+		 * For the case where num_protocols is 1,
+		 * phy_t1 = phy_t2 and the swap is unnecessary.
+		 *
+		 * Swapping phy_t1 and phy_t2 is only required when the
+		 * number of protocols is 2 and there are 2 or more links.
+		 */
+		if (protocol == 1) {
+			/**
+			 * If first protocol with phy_t1 is configured, then
+			 * configure the PHY for second protocol with phy_t2.
 			 * Get the array values as [phy_t2][phy_t1][ssc].
 			 */
 			swap(phy_t1, phy_t2);
 			swap(ref_clk, ref_clk1);
 		}
 
+		for (node = 0; node < cdns_phy->nsubnodes; node++) {
+			if (cdns_phy->phys[node].phy_type != phy_t1)
+				continue;
+
 			mlane = cdns_phy->phys[node].mlane;
 			ssc = cdns_phy->phys[node].ssc_mode;
 			num_lanes = cdns_phy->phys[node].num_lanes;
@@ -2561,9 +2610,10 @@ int cdns_torrent_phy_configure_multilink(struct cdns_torrent_phy *cdns_phy)
 			}
 
 			/* PHY PMA common registers configurations */
-		phy_pma_cmn_vals = cdns_torrent_get_tbl_vals(&init_data->phy_pma_cmn_vals_tbl,
-							     CLK_ANY, CLK_ANY,
-							     phy_t1, phy_t2, ANY_SSC);
+			phy_pma_cmn_vals =
+				cdns_torrent_get_tbl_vals(&init_data->phy_pma_cmn_vals_tbl,
+							  CLK_ANY, CLK_ANY, phy_t1, phy_t2,
+							  ANY_SSC);
 			if (phy_pma_cmn_vals) {
 				reg_pairs = phy_pma_cmn_vals->reg_pairs;
 				num_regs = phy_pma_cmn_vals->num_regs;
@@ -2624,6 +2674,7 @@ int cdns_torrent_phy_configure_multilink(struct cdns_torrent_phy *cdns_phy)
 
 			reset_control_deassert(cdns_phy->phys[node].lnk_rst);
 		}
+	}
 
 	/* Take the PHY out of reset */
 	ret = reset_control_deassert(cdns_phy->phy_rst);
@@ -2826,6 +2877,7 @@ static int cdns_torrent_phy_probe(struct platform_device *pdev)
 	dev_set_drvdata(dev, cdns_phy);
 	cdns_phy->dev = dev;
 	cdns_phy->init_data = data;
+	cdns_phy->protocol_bitmask = 0;
 
 	cdns_phy->sd_base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(cdns_phy->sd_base))
@@ -3010,6 +3062,7 @@ static int cdns_torrent_phy_probe(struct platform_device *pdev)
 		}
 
 		cdns_phy->phys[node].phy = gphy;
+		cdns_phy->protocol_bitmask |= BIT(cdns_phy->phys[node].phy_type);
 		phy_set_drvdata(gphy, &cdns_phy->phys[node]);
 
 		node++;