From b19111bb23044c9312d13e64dd1df2a9565f6b38 Mon Sep 17 00:00:00 2001
From: Artem Senichev <a.senichev@yadro.com>
Date: Wed, 12 Feb 2020 14:05:15 +0300
Subject: [PATCH] Add NCSI channel selector

NCSI channel number is selected depending on GPIO state of a pin
described in the device tree (gpio/nsci_cfg node).
Currently, this pin is controlled via MCU, and its state represents
Nicole's physical position inside a fabric.

Channel selector scheme:
* GPIO pin value is 0: channel 0;
* GPIO pin value is 1: channel 1;
* invalid configuration or error: channel 0.

After changing pin's state it is necessary to reboot the BMC to apply
new channel number.

Signed-off-by: Artem Senichev <a.senichev@yadro.com>
---
 net/ncsi/ncsi-rsp.c | 80 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 79 insertions(+), 1 deletion(-)

diff --git a/net/ncsi/ncsi-rsp.c b/net/ncsi/ncsi-rsp.c
index d876bd55f356..d211a7e64b14 100644
--- a/net/ncsi/ncsi-rsp.c
+++ b/net/ncsi/ncsi-rsp.c
@@ -9,6 +9,9 @@
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/skbuff.h>
+#include <linux/of.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 
 #include <net/ncsi.h>
 #include <net/net_namespace.h>
@@ -19,6 +22,81 @@
 #include "ncsi-pkt.h"
 #include "ncsi-netlink.h"
 
+/* NSCI channel number, used as default in case of errors. */
+#define NCSI_DEFAULT_CHANNEL 0
+
+/* Predicate for gpiochip_find() call. */
+static int device_match(struct gpio_chip* chip, void* data)
+{
+	const struct device_node *node = data;
+	return chip->of_node == node;
+}
+
+/**
+ * ncsi_select_channel() - Get channel number for NCSI.
+ * @dev: Network device.
+ *
+ * NCSI channel number is selected depending on GPIO state of a pin
+ * described in the device tree (gpio/nsci_cfg node).
+ *
+ * Return: channel number.
+ */
+static int ncsi_select_channel(const struct net_device* dev)
+{
+	static int channel_id = -1;
+	struct device_node* node = NULL;
+
+	while (channel_id < 0) {
+		struct gpio_chip* chip;
+		const struct gpio_desc* desc;
+		u32 pin;
+		int rc;
+
+		/* Read NCSI configuration node from device tree */
+		node = of_find_node_by_name(NULL, "ncsi_cfg");
+		if (!node) {
+			netdev_err(dev, "NCSI: Configuration node not found\n");
+			break;
+		}
+
+		/* Read GPIO pin configuration */
+		rc = of_property_read_u32_index(node, "gpios", 0, &pin);
+		if (rc) {
+			netdev_err(dev, "NCSI: GPIO configuration not found\n");
+			break;
+		}
+
+		/* Find GPIO chip */
+		chip = gpiochip_find(node->parent, device_match);
+		if (!chip) {
+			netdev_err(dev, "NCSI: GPIO chip not found\n");
+			break;
+		}
+
+		/* Read GPIO state */
+		desc = gpio_to_desc(chip->base + pin);
+		if (!desc) {
+			netdev_err(dev, "NCSI: Cannot get GPIO descriptor\n");
+			break;
+		}
+		channel_id = gpiod_get_value(desc);
+		if (channel_id < 0) {
+			netdev_err(dev, "NCSI: GPIO read error %d\n", channel_id);
+		}
+		break;
+	}
+
+	if (node) {
+		of_node_put(node);
+	}
+	if (channel_id < 0) {
+		channel_id = NCSI_DEFAULT_CHANNEL;
+	}
+	netdev_info(dev, "NCSI: Set channel %d\n", channel_id);
+
+	return channel_id;
+}
+
 static int ncsi_validate_rsp_pkt(struct ncsi_request *nr,
 				 unsigned short payload)
 {
@@ -87,7 +165,7 @@ static int ncsi_rsp_handler_cis(struct ncsi_request *nr)
 		if (ndp->flags & NCSI_DEV_PROBED)
 			return -ENXIO;
 
-		id = NCSI_CHANNEL_INDEX(rsp->rsp.common.channel);
+		id = ncsi_select_channel(ndp->ndev.dev);
 		nc = ncsi_add_channel(np, id);
 	}
 
-- 
2.25.0