thunderbolt: Read switch uid from EEPROM

Add eeprom access code and read the uid during switch initialization.
The UID will be used to check device identity after suspend.
Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/thunderbolt/Makefile

 obj-${CONFIG_THUNDERBOLT} := thunderbolt.o
-thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o path.o tunnel_pci.o
+thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o path.o tunnel_pci.o eeprom.o
 

drivers/thunderbolt/eeprom.c

+/*
+ * Thunderbolt Cactus Ridge driver - eeprom access
+ *
+ * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
+ */
+
+#include "tb.h"
+
+/**
+ * tb_eeprom_ctl_write() - write control word
+ */
+static int tb_eeprom_ctl_write(struct tb_switch *sw, struct tb_eeprom_ctl *ctl)
+{
+	return tb_sw_write(sw, ctl, TB_CFG_SWITCH, sw->cap_plug_events + 4, 1);
+}
+
+/**
+ * tb_eeprom_ctl_write() - read control word
+ */
+static int tb_eeprom_ctl_read(struct tb_switch *sw, struct tb_eeprom_ctl *ctl)
+{
+	return tb_sw_read(sw, ctl, TB_CFG_SWITCH, sw->cap_plug_events + 4, 1);
+}
+
+enum tb_eeprom_transfer {
+	TB_EEPROM_IN,
+	TB_EEPROM_OUT,
+};
+
+/**
+ * tb_eeprom_active - enable rom access
+ *
+ * WARNING: Always disable access after usage. Otherwise the controller will
+ * fail to reprobe.
+ */
+static int tb_eeprom_active(struct tb_switch *sw, bool enable)
+{
+	struct tb_eeprom_ctl ctl;
+	int res = tb_eeprom_ctl_read(sw, &ctl);
+	if (res)
+		return res;
+	if (enable) {
+		ctl.access_high = 1;
+		res = tb_eeprom_ctl_write(sw, &ctl);
+		if (res)
+			return res;
+		ctl.access_low = 0;
+		return tb_eeprom_ctl_write(sw, &ctl);
+	} else {
+		ctl.access_low = 1;
+		res = tb_eeprom_ctl_write(sw, &ctl);
+		if (res)
+			return res;
+		ctl.access_high = 0;
+		return tb_eeprom_ctl_write(sw, &ctl);
+	}
+}
+
+/**
+ * tb_eeprom_transfer - transfer one bit
+ *
+ * If TB_EEPROM_IN is passed, then the bit can be retrieved from ctl->data_in.
+ * If TB_EEPROM_OUT is passed, then ctl->data_out will be written.
+ */
+static int tb_eeprom_transfer(struct tb_switch *sw, struct tb_eeprom_ctl *ctl,
+			      enum tb_eeprom_transfer direction)
+{
+	int res;
+	if (direction == TB_EEPROM_OUT) {
+		res = tb_eeprom_ctl_write(sw, ctl);
+		if (res)
+			return res;
+	}
+	ctl->clock = 1;
+	res = tb_eeprom_ctl_write(sw, ctl);
+	if (res)
+		return res;
+	if (direction == TB_EEPROM_IN) {
+		res = tb_eeprom_ctl_read(sw, ctl);
+		if (res)
+			return res;
+	}
+	ctl->clock = 0;
+	return tb_eeprom_ctl_write(sw, ctl);
+}
+
+/**
+ * tb_eeprom_out - write one byte to the bus
+ */
+static int tb_eeprom_out(struct tb_switch *sw, u8 val)
+{
+	struct tb_eeprom_ctl ctl;
+	int i;
+	int res = tb_eeprom_ctl_read(sw, &ctl);
+	if (res)
+		return res;
+	for (i = 0; i < 8; i++) {
+		ctl.data_out = val & 0x80;
+		res = tb_eeprom_transfer(sw, &ctl, TB_EEPROM_OUT);
+		if (res)
+			return res;
+		val <<= 1;
+	}
+	return 0;
+}
+
+/**
+ * tb_eeprom_in - read one byte from the bus
+ */
+static int tb_eeprom_in(struct tb_switch *sw, u8 *val)
+{
+	struct tb_eeprom_ctl ctl;
+	int i;
+	int res = tb_eeprom_ctl_read(sw, &ctl);
+	if (res)
+		return res;
+	*val = 0;
+	for (i = 0; i < 8; i++) {
+		*val <<= 1;
+		res = tb_eeprom_transfer(sw, &ctl, TB_EEPROM_IN);
+		if (res)
+			return res;
+		*val |= ctl.data_in;
+	}
+	return 0;
+}
+
+/**
+ * tb_eeprom_read_n - read count bytes from offset into val
+ */
+static int tb_eeprom_read_n(struct tb_switch *sw, u16 offset, u8 *val,
+		size_t count)
+{
+	int i, res;
+	res = tb_eeprom_active(sw, true);
+	if (res)
+		return res;
+	res = tb_eeprom_out(sw, 3);
+	if (res)
+		return res;
+	res = tb_eeprom_out(sw, offset >> 8);
+	if (res)
+		return res;
+	res = tb_eeprom_out(sw, offset);
+	if (res)
+		return res;
+	for (i = 0; i < count; i++) {
+		res = tb_eeprom_in(sw, val + i);
+		if (res)
+			return res;
+	}
+	return tb_eeprom_active(sw, false);
+}
+
+int tb_eeprom_read_uid(struct tb_switch *sw, u64 *uid)
+{
+	u8 data[9];
+	struct tb_cap_plug_events cap;
+	int res;
+	if (!sw->cap_plug_events) {
+		tb_sw_warn(sw, "no TB_CAP_PLUG_EVENTS, cannot read eeprom\n");
+		return -ENOSYS;
+	}
+	res = tb_sw_read(sw, &cap, TB_CFG_SWITCH, sw->cap_plug_events,
+			     sizeof(cap) / 4);
+	if (res)
+		return res;
+	if (!cap.eeprom_ctl.present || cap.eeprom_ctl.not_present) {
+		tb_sw_warn(sw, "no NVM\n");
+		return -ENOSYS;
+	}
+
+	if (cap.drom_offset > 0xffff) {
+		tb_sw_warn(sw, "drom offset is larger than 0xffff: %#x\n",
+				cap.drom_offset);
+		return -ENXIO;
+	}
+
+	/* read uid */
+	res = tb_eeprom_read_n(sw, cap.drom_offset, data, 9);
+	if (res)
+		return res;
+	/* TODO: check checksum in data[0] */
+	*uid = *(u64 *)(data+1);
+	return 0;
+}
+
+
+

drivers/thunderbolt/switch.c

@@ -376,6 +376,11 @@ struct tb_switch *tb_switch_alloc(struct tb *tb, u64 route)
 	}
 	sw->cap_plug_events = cap;
 
+	if (tb_eeprom_read_uid(sw, &sw->uid))
+		tb_sw_warn(sw, "could not read uid from eeprom\n");
+	else
+		tb_sw_info(sw, "uid: %#llx\n", sw->uid);
+
 	if (tb_plug_events_active(sw, true))
 		goto err;
 

drivers/thunderbolt/tb.h

@@ -19,6 +19,7 @@ struct tb_switch {
 	struct tb_regs_switch_header config;
 	struct tb_port *ports;
 	struct tb *tb;
+	u64 uid;
 	int cap_plug_events; /* offset, zero if not found */
 	bool is_unplugged; /* unplugged, will go away */
 };
@@ -231,6 +232,8 @@ int tb_path_activate(struct tb_path *path);
 void tb_path_deactivate(struct tb_path *path);
 bool tb_path_is_invalid(struct tb_path *path);
 
+int tb_eeprom_read_uid(struct tb_switch *sw, u64 *uid);
+
 
 static inline int tb_route_length(u64 route)
 {