thunderbolt: Add thunderbolt capability handling

Thunderbolt config areas contain capability lists similar to those found
on pci devices. This patch introduces a tb_find_cap utility method to
search for capabilities.

Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/thunderbolt/Makefile b/drivers/thunderbolt/Makefile
index 4ac18d969306e0518efd35a74bebcd92101aac1e..617b31480b2eb5930008802a061211aea1cd9772 100644 (file)
--- a/drivers/thunderbolt/Makefile
+++ b/drivers/thunderbolt/Makefile
@@ -1,3 +1,3 @@
 obj-${CONFIG_THUNDERBOLT} := thunderbolt.o
-thunderbolt-objs := nhi.o ctl.o tb.o switch.o
+thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o
 

diff --git a/drivers/thunderbolt/cap.c b/drivers/thunderbolt/cap.c
new file mode 100644 (file)
index 0000000..a7b47e7
--- /dev/null
+++ b/drivers/thunderbolt/cap.c
@@ -0,0 +1,116 @@
+/*
+ * Thunderbolt Cactus Ridge driver - capabilities lookup
+ *
+ * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/errno.h>
+
+#include "tb.h"
+
+
+struct tb_cap_any {
+       union {
+               struct tb_cap_basic basic;
+               struct tb_cap_extended_short extended_short;
+               struct tb_cap_extended_long extended_long;
+       };
+} __packed;
+
+static bool tb_cap_is_basic(struct tb_cap_any *cap)
+{
+       /* basic.cap is u8. This checks only the lower 8 bit of cap. */
+       return cap->basic.cap != 5;
+}
+
+static bool tb_cap_is_long(struct tb_cap_any *cap)
+{
+       return !tb_cap_is_basic(cap)
+              && cap->extended_short.next == 0
+              && cap->extended_short.length == 0;
+}
+
+static enum tb_cap tb_cap(struct tb_cap_any *cap)
+{
+       if (tb_cap_is_basic(cap))
+               return cap->basic.cap;
+       else
+               /* extended_short/long have cap at the same offset. */
+               return cap->extended_short.cap;
+}
+
+static u32 tb_cap_next(struct tb_cap_any *cap, u32 offset)
+{
+       int next;
+       if (offset == 1) {
+               /*
+                * The first pointer is part of the switch header and always
+                * a simple pointer.
+                */
+               next = cap->basic.next;
+       } else {
+               /*
+                * Somehow Intel decided to use 3 different types of capability
+                * headers. It is not like anyone could have predicted that
+                * single byte offsets are not enough...
+                */
+               if (tb_cap_is_basic(cap))
+                       next = cap->basic.next;
+               else if (!tb_cap_is_long(cap))
+                       next = cap->extended_short.next;
+               else
+                       next = cap->extended_long.next;
+       }
+       /*
+        * "Hey, we could terminate some capability lists with a null offset
+        *  and others with a pointer to the last element." - "Great idea!"
+        */
+       if (next == offset)
+               return 0;
+       return next;
+}
+
+/**
+ * tb_find_cap() - find a capability
+ *
+ * Return: Returns a positive offset if the capability was found and 0 if not.
+ * Returns an error code on failure.
+ */
+int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, enum tb_cap cap)
+{
+       u32 offset = 1;
+       struct tb_cap_any header;
+       int res;
+       int retries = 10;
+       while (retries--) {
+               res = tb_port_read(port, &header, space, offset, 1);
+               if (res) {
+                       /* Intel needs some help with linked lists. */
+                       if (space == TB_CFG_PORT && offset == 0xa
+                           && port->config.type == TB_TYPE_DP_HDMI_OUT) {
+                               offset = 0x39;
+                               continue;
+                       }
+                       return res;
+               }
+               if (offset != 1) {
+                       if (tb_cap(&header) == cap)
+                               return offset;
+                       if (tb_cap_is_long(&header)) {
+                               /* tb_cap_extended_long is 2 dwords */
+                               res = tb_port_read(port, &header, space,
+                                                  offset, 2);
+                               if (res)
+                                       return res;
+                       }
+               }
+               offset = tb_cap_next(&header, offset);
+               if (!offset)
+                       return 0;
+       }
+       tb_port_WARN(port,
+                    "run out of retries while looking for cap %#x in config space %d, last offset: %#x\n",
+                    cap, space, offset);
+       return -EIO;
+}

diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 389dbb405c5f234fe7e25286cb8cd124169e2440..38e4c23c10fdf07bcd9d8208af56eaedc9bc289d 100644 (file)
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -159,6 +159,8 @@ void thunderbolt_shutdown_and_free(struct tb *tb);
 struct tb_switch *tb_switch_alloc(struct tb *tb, u64 route);
 void tb_switch_free(struct tb_switch *sw);
 
+int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, u32 value);
+
 
 static inline int tb_route_length(u64 route)
 {