regmap: introduce regmap_name to fix syscon regmap trace events

This patch fixes a NULL pointer dereference when enabling regmap event
tracing in the presence of a syscon regmap, introduced by commit bdb0066
("mfd: syscon: Decouple syscon interface from platform devices").
That patch introduced syscon regmaps that have their dev field set to NULL.
The regmap trace events expect it to point to a valid struct device and feed
it to dev_name():

  $ echo 1 > /sys/kernel/debug/tracing/events/regmap/enable

  Unable to handle kernel NULL pointer dereference at virtual address 0000002c
  pgd = 80004000
  [0000002c] *pgd=00000000
  Internal error: Oops: 17 [#1] SMP ARM
  Modules linked in: coda videobuf2_vmalloc
  CPU: 0 PID: 304 Comm: kworker/0:2 Not tainted 4.0.0-rc2+ #9197
  Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
  Workqueue: events_freezable thermal_zone_device_check
  task: 9f25a200 ti: 9f1ee000 task.ti: 9f1ee000
  PC is at ftrace_raw_event_regmap_block+0x3c/0xe4
  LR is at _regmap_raw_read+0x1bc/0x1cc
  pc : [<803636e8>]    lr : [<80365f2c>]    psr: 600f0093
  sp : 9f1efd78  ip : 9f1efdb8  fp : 9f1efdb4
  r10: 00000004  r9 : 00000001  r8 : 00000001
  r7 : 00000180  r6 : 00000000  r5 : 9f00e3c0  r4 : 00000003
  r3 : 00000001  r2 : 00000180  r1 : 00000000  r0 : 9f00e3c0
  Flags: nZCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
  Control: 10c5387d  Table: 2d91004a  DAC: 00000015
  Process kworker/0:2 (pid: 304, stack limit = 0x9f1ee210)
  Stack: (0x9f1efd78 to 0x9f1f0000)
  fd60:                                                       9f1efda4 9f1efd88
  fd80: 800708c0 805f9510 80927140 800f0013 9f1fc800 9eb2f490 00000000 00000180
  fda0: 808e3840 00000001 9f1efdfc 9f1efdb8 80365f2c 803636b8 805f8958 800708e0
  fdc0: a00f0013 803636ac 9f16de00 00000180 80927140 9f1fc800 9f1fc800 9f1efe6c
  fde0: 9f1efe6c 9f732400 00000000 00000000 9f1efe1c 9f1efe00 80365f70 80365d7c
  fe00: 80365f3c 9f1fc800 9f1fc800 00000180 9f1efe44 9f1efe20 803656a4 80365f48
  fe20: 9f1fc800 00000180 9f1efe6c 9f1efe6c 9f732400 00000000 9f1efe64 9f1efe48
  fe40: 803657bc 80365634 00000001 9e95f910 9f1fc800 9f1efeb4 9f1efe8c 9f1efe68
  fe60: 80452ac0 80365778 9f1efe8c 9f1efe78 9e93d400 9e93d5e8 9f1efeb4 9f72ef40
  fe80: 9f1efeac 9f1efe90 8044e11c 80452998 8045298c 9e93d608 9e93d400 808e1978
  fea0: 9f1efec 9f1efeb0 8044fd14 8044e0d0 ffffffff 9f25a200 9e93d608 9e481380
  fec0: 9f1efedc 9f1efed0 8044fde8 8044fcec 9f1eff1c 9f1efee0 80038d50 8044fdd8
  fee0: 9f1ee020 9f72ef40 9e481398 00000000 00000008 9f72ef54 9f1ee020 9f72ef40
  ff00: 9e481398 9e481380 00000008 9f72ef40 9f1eff5c 9f1eff20 80039754 80038bfc
  ff20: 00000000 9e481380 80894100 808e1662 00000000 9e4f2ec 00000000 9e481380
  ff40: 800396f 00000000 00000000 00000000 9f1effac 9f1eff60 8003e02 80039704
  ff60: ffffffff 00000000 ffffffff 9e481380 00000000 00000000 9f1eff78 9f1eff78
  ff80: 00000000 00000000 9f1eff88 9f1eff88 9e4f2ec 8003df30 00000000 00000000
  ffa0: 00000000 9f1effb0 8000eb60 8003df3c 00000000 00000000 00000000 00000000
  ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
  ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 ffffffff ffffffff
  Backtrace:
  [<803636ac>] (ftrace_raw_event_regmap_block) from [<80365f2c>] (_regmap_raw_read+0x1bc/0x1cc)
   r9:00000001 r8:808e3840 r7:00000180 r6:00000000 r5:9eb2f490 r4:9f1fc800
  [<80365d70>] (_regmap_raw_read) from [<80365f70>] (_regmap_bus_read+0x34/0x6c)
   r10:00000000 r9:00000000 r8:9f732400 r7:9f1efe6c r6:9f1efe6c r5:9f1fc800
   r4:9f1fc800
  [<80365f3c>] (_regmap_bus_read) from [<803656a4>] (_regmap_read+0x7c/0x144)
   r6:00000180 r5:9f1fc800 r4:9f1fc800 r3:80365f3c
  [<80365628>] (_regmap_read) from [<803657bc>] (regmap_read+0x50/0x70)
   r9:00000000 r8:9f732400 r7:9f1efe6c r6:9f1efe6c r5:00000180 r4:9f1fc800
  [<8036576c>] (regmap_read) from [<80452ac0>] (imx_get_temp+0x134/0x1a4)
   r6:9f1efeb4 r5:9f1fc800 r4:9e95f910 r3:00000001
  [<8045298c>] (imx_get_temp) from [<8044e11c>] (thermal_zone_get_temp+0x58/0x74)
   r7:9f72ef40 r6:9f1efeb4 r5:9e93d5e8 r4:9e93d400
  [<8044e0c4>] (thermal_zone_get_temp) from [<8044fd14>] (thermal_zone_device_update+0x34/0xec)
   r6:808e1978 r5:9e93d400 r4:9e93d608 r3:8045298c
  [<8044fce0>] (thermal_zone_device_update) from [<8044fde8>] (thermal_zone_device_check+0x1c/0x20)
   r5:9e481380 r4:9e93d608
  [<8044fdcc>] (thermal_zone_device_check) from [<80038d50>] (process_one_work+0x160/0x3d4)
  [<80038bf0>] (process_one_work) from [<80039754>] (worker_thread+0x5c/0x4f4)
   r10:9f72ef40 r9:00000008 r8:9e481380 r7:9e481398 r6:9f72ef40 r5:9f1ee020
   r4:9f72ef54
  [<800396f8>] (worker_thread) from [<8003e020>] (kthread+0xf0/0x108)
   r10:00000000 r9:00000000 r8:00000000 r7:800396f8 r6:9e481380 r5:00000000
   r4:9e4f2ec0
  [<8003df30>] (kthread) from [<8000eb60>] (ret_from_fork+0x14/0x34)
   r7:00000000 r6:00000000 r5:8003df30 r4:9e4f2ec0
  Code: e3140040 1a00001a e3140020 1a00001 (e596002c)
  ---[ end trace 193c15c2494ec960 ]---

Fixes: bdb0066 (mfd: syscon: Decouple syscon interface from platform devices)
Signed-off-by: Philipp Zabel <[email protected]>
Signed-off-by: Mark Brown <[email protected]>
Cc: [email protected]

Author: pH5

drivers/base/regmap/internal.h

@@ -243,4 +243,12 @@ extern struct regcache_ops regcache_rbtree_ops;
 extern struct regcache_ops regcache_lzo_ops;
 extern struct regcache_ops regcache_flat_ops;
 
+static inline const char *regmap_name(const struct regmap *map)
+{
+	if (map->dev)
+		return dev_name(map->dev);
+
+	return map->name;
+}
+
 #endif

drivers/base/regmap/regcache.c

@@ -218,7 +218,7 @@ int regcache_read(struct regmap *map,
 		ret = map->cache_ops->read(map, reg, value);
 
 		if (ret == 0)
-			trace_regmap_reg_read_cache(map->dev, reg, *value);
+			trace_regmap_reg_read_cache(map, reg, *value);
 
 		return ret;
 	}
@@ -311,7 +311,7 @@ int regcache_sync(struct regmap *map)
 	dev_dbg(map->dev, "Syncing %s cache\n",
 		map->cache_ops->name);
 	name = map->cache_ops->name;
-	trace_regcache_sync(map->dev, name, "start");
+	trace_regcache_sync(map, name, "start");
 
 	if (!map->cache_dirty)
 		goto out;
@@ -346,7 +346,7 @@ int regcache_sync(struct regmap *map)
 
 	regmap_async_complete(map);
 
-	trace_regcache_sync(map->dev, name, "stop");
+	trace_regcache_sync(map, name, "stop");
 
 	return ret;
 }
@@ -381,7 +381,7 @@ int regcache_sync_region(struct regmap *map, unsigned int min,
 	name = map->cache_ops->name;
 	dev_dbg(map->dev, "Syncing %s cache from %d-%d\n", name, min, max);
 
-	trace_regcache_sync(map->dev, name, "start region");
+	trace_regcache_sync(map, name, "start region");
 
 	if (!map->cache_dirty)
 		goto out;
@@ -401,7 +401,7 @@ int regcache_sync_region(struct regmap *map, unsigned int min,
 
 	regmap_async_complete(map);
 
-	trace_regcache_sync(map->dev, name, "stop region");
+	trace_regcache_sync(map, name, "stop region");
 
 	return ret;
 }
@@ -428,7 +428,7 @@ int regcache_drop_region(struct regmap *map, unsigned int min,
 
 	map->lock(map->lock_arg);
 
-	trace_regcache_drop_region(map->dev, min, max);
+	trace_regcache_drop_region(map, min, max);
 
 	ret = map->cache_ops->drop(map, min, max);
 
@@ -455,7 +455,7 @@ void regcache_cache_only(struct regmap *map, bool enable)
 	map->lock(map->lock_arg);
 	WARN_ON(map->cache_bypass && enable);
 	map->cache_only = enable;
-	trace_regmap_cache_only(map->dev, enable);
+	trace_regmap_cache_only(map, enable);
 	map->unlock(map->lock_arg);
 }
 EXPORT_SYMBOL_GPL(regcache_cache_only);
@@ -493,7 +493,7 @@ void regcache_cache_bypass(struct regmap *map, bool enable)
 	map->lock(map->lock_arg);
 	WARN_ON(map->cache_only && enable);
 	map->cache_bypass = enable;
-	trace_regmap_cache_bypass(map->dev, enable);
+	trace_regmap_cache_bypass(map, enable);
 	map->unlock(map->lock_arg);
 }
 EXPORT_SYMBOL_GPL(regcache_cache_bypass);

drivers/base/regmap/regmap.c

@@ -1281,7 +1281,7 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 	if (map->async && map->bus->async_write) {
 		struct regmap_async *async;
 
-		trace_regmap_async_write_start(map->dev, reg, val_len);
+		trace_regmap_async_write_start(map, reg, val_len);
 
 		spin_lock_irqsave(&map->async_lock, flags);
 		async = list_first_entry_or_null(&map->async_free,
@@ -1339,8 +1339,7 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 		return ret;
 	}
 
-	trace_regmap_hw_write_start(map->dev, reg,
-				    val_len / map->format.val_bytes);
+	trace_regmap_hw_write_start(map, reg, val_len / map->format.val_bytes);
 
 	/* If we're doing a single register write we can probably just
 	 * send the work_buf directly, otherwise try to do a gather
@@ -1372,8 +1371,7 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 		kfree(buf);
 	}
 
-	trace_regmap_hw_write_done(map->dev, reg,
-				   val_len / map->format.val_bytes);
+	trace_regmap_hw_write_done(map, reg, val_len / map->format.val_bytes);
 
 	return ret;
 }
@@ -1407,12 +1405,12 @@ static int _regmap_bus_formatted_write(void *context, unsigned int reg,
 
 	map->format.format_write(map, reg, val);
 
-	trace_regmap_hw_write_start(map->dev, reg, 1);
+	trace_regmap_hw_write_start(map, reg, 1);
 
 	ret = map->bus->write(map->bus_context, map->work_buf,
 			      map->format.buf_size);
 
-	trace_regmap_hw_write_done(map->dev, reg, 1);
+	trace_regmap_hw_write_done(map, reg, 1);
 
 	return ret;
 }
@@ -1470,7 +1468,7 @@ int _regmap_write(struct regmap *map, unsigned int reg,
 		dev_info(map->dev, "%x <= %x\n", reg, val);
 #endif
 
-	trace_regmap_reg_write(map->dev, reg, val);
+	trace_regmap_reg_write(map, reg, val);
 
 	return map->reg_write(context, reg, val);
 }
@@ -1773,7 +1771,7 @@ static int _regmap_raw_multi_reg_write(struct regmap *map,
 	for (i = 0; i < num_regs; i++) {
 		int reg = regs[i].reg;
 		int val = regs[i].def;
-		trace_regmap_hw_write_start(map->dev, reg, 1);
+		trace_regmap_hw_write_start(map, reg, 1);
 		map->format.format_reg(u8, reg, map->reg_shift);
 		u8 += reg_bytes + pad_bytes;
 		map->format.format_val(u8, val, 0);
@@ -1788,7 +1786,7 @@ static int _regmap_raw_multi_reg_write(struct regmap *map,
 
 	for (i = 0; i < num_regs; i++) {
 		int reg = regs[i].reg;
-		trace_regmap_hw_write_done(map->dev, reg, 1);
+		trace_regmap_hw_write_done(map, reg, 1);
 	}
 	return ret;
 }
@@ -2059,15 +2057,13 @@ static int _regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 	 */
 	u8[0] |= map->read_flag_mask;
 
-	trace_regmap_hw_read_start(map->dev, reg,
-				   val_len / map->format.val_bytes);
+	trace_regmap_hw_read_start(map, reg, val_len / map->format.val_bytes);
 
 	ret = map->bus->read(map->bus_context, map->work_buf,
 			     map->format.reg_bytes + map->format.pad_bytes,
 			     val, val_len);
 
-	trace_regmap_hw_read_done(map->dev, reg,
-				  val_len / map->format.val_bytes);
+	trace_regmap_hw_read_done(map, reg, val_len / map->format.val_bytes);
 
 	return ret;
 }
@@ -2123,7 +2119,7 @@ static int _regmap_read(struct regmap *map, unsigned int reg,
 			dev_info(map->dev, "%x => %x\n", reg, *val);
 #endif
 
-		trace_regmap_reg_read(map->dev, reg, *val);
+		trace_regmap_reg_read(map, reg, *val);
 
 		if (!map->cache_bypass)
 			regcache_write(map, reg, *val);
@@ -2480,7 +2476,7 @@ void regmap_async_complete_cb(struct regmap_async *async, int ret)
 	struct regmap *map = async->map;
 	bool wake;
 
-	trace_regmap_async_io_complete(map->dev);
+	trace_regmap_async_io_complete(map);
 
 	spin_lock(&map->async_lock);
 	list_move(&async->list, &map->async_free);
@@ -2525,7 +2521,7 @@ int regmap_async_complete(struct regmap *map)
 	if (!map->bus || !map->bus->async_write)
 		return 0;
 
-	trace_regmap_async_complete_start(map->dev);
+	trace_regmap_async_complete_start(map);
 
 	wait_event(map->async_waitq, regmap_async_is_done(map));
 
@@ -2534,7 +2530,7 @@ int regmap_async_complete(struct regmap *map)
 	map->async_ret = 0;
 	spin_unlock_irqrestore(&map->async_lock, flags);
 
-	trace_regmap_async_complete_done(map->dev);
+	trace_regmap_async_complete_done(map);
 
 	return ret;
 }