[PATCH v3] drivers: cpufreq: Fix sysfs duplicate filename creation for platform-device

[sunil.m@techveda.org]

From: Suniel Mahesh <sunil.m@techveda.org>

ti-cpufreq and cpufreq-dt-platdev drivers are registering platform-device
with same name "cpufreq-dt" using platform_device_register_*() routines.
This is leading to build warnings appended below.

Providing hardware information to OPP framework along with the platform-
device creation should be done by ti-cpufreq driver before cpufreq-dt
driver comes into place.

This patch add's TI am33xx, am43 and dra7 platforms (which use opp-v2
property) to the blacklist of devices in cpufreq-dt-platform driver to
avoid creating platform-device twice and remove build warnings.

[    2.370167] ------------[ cut here ]------------
[    2.375087] WARNING: CPU: 0 PID: 1 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x58/0x78
[    2.383112] sysfs: cannot create duplicate filename '/devices/platform/cpufreq-dt'
[    2.391219] Modules linked in:
[    2.394506] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.13.0-next-20170912 #1
[    2.402006] Hardware name: Generic AM33XX (Flattened Device Tree)
[    2.408437] [<c0110a28>] (unwind_backtrace) from [<c010ca84>] (show_stack+0x10/0x14)
[    2.416568] [<c010ca84>] (show_stack) from [<c0827d64>] (dump_stack+0xac/0xe0)
[    2.424165] [<c0827d64>] (dump_stack) from [<c0137470>] (__warn+0xd8/0x104)
[    2.431488] [<c0137470>] (__warn) from [<c01374d0>] (warn_slowpath_fmt+0x34/0x44)
[    2.439351] [<c01374d0>] (warn_slowpath_fmt) from [<c03459d0>] (sysfs_warn_dup+0x58/0x78)
[    2.447938] [<c03459d0>] (sysfs_warn_dup) from [<c0345ab8>] (sysfs_create_dir_ns+0x80/0x98)
[    2.456719] [<c0345ab8>] (sysfs_create_dir_ns) from [<c082c554>] (kobject_add_internal+0x9c/0x2d4)
[    2.466124] [<c082c554>] (kobject_add_internal) from [<c082c7d8>] (kobject_add+0x4c/0x9c)
[    2.474712] [<c082c7d8>] (kobject_add) from [<c05803e4>] (device_add+0xcc/0x57c)
[    2.482489] [<c05803e4>] (device_add) from [<c0584b74>] (platform_device_add+0x100/0x220)
[    2.491085] [<c0584b74>] (platform_device_add) from [<c05855a8>] (platform_device_register_full+0xf4/0x118)
[    2.501305] [<c05855a8>] (platform_device_register_full) from [<c067023c>] (ti_cpufreq_init+0x150/0x22c)
[    2.511253] [<c067023c>] (ti_cpufreq_init) from [<c0101df4>] (do_one_initcall+0x3c/0x170)
[    2.519838] [<c0101df4>] (do_one_initcall) from [<c0c00eb4>] (kernel_init_freeable+0x1fc/0x2c4)
[    2.528974] [<c0c00eb4>] (kernel_init_freeable) from [<c083bcac>] (kernel_init+0x8/0x110)
[    2.537565] [<c083bcac>] (kernel_init) from [<c0107d18>] (ret_from_fork+0x14/0x3c)
[    2.545981] ---[ end trace 2fc00e213c13ab20 ]---
[    2.551051] ------------[ cut here ]------------
[    2.555931] WARNING: CPU: 0 PID: 1 at lib/kobject.c:240 kobject_add_internal+0x254/0x2d4
[    2.564578] kobject_add_internal failed for cpufreq-dt with -EEXIST, don't try to register
things with the same name in the same directory.
[    2.577977] Modules linked in:
[    2.581261] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W       4.13.0-next-20170912 #1
[    2.590013] Hardware name: Generic AM33XX (Flattened Device Tree)
[    2.596437] [<c0110a28>] (unwind_backtrace) from [<c010ca84>] (show_stack+0x10/0x14)
[    2.604573] [<c010ca84>] (show_stack) from [<c0827d64>] (dump_stack+0xac/0xe0)
[    2.612172] [<c0827d64>] (dump_stack) from [<c0137470>] (__warn+0xd8/0x104)
[    2.619494] [<c0137470>] (__warn) from [<c01374d0>] (warn_slowpath_fmt+0x34/0x44)
[    2.627362] [<c01374d0>] (warn_slowpath_fmt) from [<c082c70c>] (kobject_add_internal+0x254/0x2d4)
[    2.636666] [<c082c70c>] (kobject_add_internal) from [<c082c7d8>] (kobject_add+0x4c/0x9c)
[    2.645255] [<c082c7d8>] (kobject_add) from [<c05803e4>] (device_add+0xcc/0x57c)
[    2.653027] [<c05803e4>] (device_add) from [<c0584b74>] (platform_device_add+0x100/0x220)
[    2.661615] [<c0584b74>] (platform_device_add) from [<c05855a8>] (platform_device_register_full+0xf4/0x118)
[    2.671833] [<c05855a8>] (platform_device_register_full) from [<c067023c>] (ti_cpufreq_init+0x150/0x22c)
[    2.681779] [<c067023c>] (ti_cpufreq_init) from [<c0101df4>] (do_one_initcall+0x3c/0x170)
[    2.690377] [<c0101df4>] (do_one_initcall) from [<c0c00eb4>] (kernel_init_freeable+0x1fc/0x2c4)
[    2.699510] [<c0c00eb4>] (kernel_init_freeable) from [<c083bcac>] (kernel_init+0x8/0x110)
[    2.708106] [<c083bcac>] (kernel_init) from [<c0107d18>] (ret_from_fork+0x14/0x3c)
[    2.716217] ---[ end trace 2fc00e213c13ab21 ]---

Fixes: edeec420de24 ("cpufreq: dt-cpufreq: platdev Automatically create device with OPP v2")
Signed-off-by: Suniel Mahesh <sunil.m@techveda.org>
---
Changes for v3:
- Added ti,am43 and ti,dra7 platforms to the blacklist as requested
  by Dave Gerlach.
- Patch Description modified a bit.
- Patch was rebased on pm/linux-next as suggested by Viresh, compile
  tested and built(ARCH=arm) on both linux/pm-next and next-20170918.
---
Changes for v2:
- The approach (as a result patch decsription) was changed as per
  inputs given by Viresh.
- Patch was compile tested and built(ARCH=arm) on next-20170918.
---
Note:
- Patch was hardware tested on AM335x SOC based board.
- cpufreq-dt driver got probed and entries related to Dynamic Voltage
  and Frequency scaling were created in
  sysfs @ sys/devices/system/cpu/cpu0/cpufreq.
- No build/run-time issues reported.
---
 drivers/cpufreq/cpufreq-dt-platdev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/cpufreq/cpufreq-dt-platdev.c b/drivers/cpufreq/cpufreq-dt-platdev.c
index 430edad..a753c50 100644
--- a/drivers/cpufreq/cpufreq-dt-platdev.c
+++ b/drivers/cpufreq/cpufreq-dt-platdev.c
@@ -118,6 +118,10 @@
 
 	{ .compatible = "sigma,tango4", },
 
+	{ .compatible = "ti,am33xx", },
+	{ .compatible = "ti,am43", },
+	{ .compatible = "ti,dra7", },
+
 	{ }
 };
 
-- 
1.9.1