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Message-id: <56138C9F.7040609@samsung.com>
Date: Tue, 06 Oct 2015 10:55:59 +0200
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Felipe Balbi <balbi@...com>, John Youn <John.Youn@...opsys.com>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-samsung-soc@...r.kernel.org"
<linux-samsung-soc@...r.kernel.org>
Cc: Robert Baldyga <r.baldyga@...sung.com>,
Krzysztof Kozlowski <k.kozlowski@...sung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v4 4/4] usb: dwc2: refactor common low-level hw code to
platform.c
Hello,
On 2015-10-06 01:27, Felipe Balbi wrote:
> John Youn <John.Youn@...opsys.com> writes:
>
> Hi,
>
>> On 10/2/2015 12:45 AM, Marek Szyprowski wrote:
>>> DWC2 module on some platforms needs three additional hardware
>>> resources: phy controller, clock and power supply. All of them must be
>>> enabled/activated to properly initialize and operate. This was initially
>>> handled in s3c-hsotg driver, which has been converted to 'gadget' part
>>> of dwc2 driver. Unfortunately, not all of this code got moved to common
>>> platform code, what resulted in accessing DWC2 registers without
>>> enabling low-level hardware resources. This fails for example on Exynos
>>> SoCs. This patch moves all the code for managing those resources to
>>> common platform.c file and provides convenient wrappers for controlling
>>> them.
>>>
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
>>> ---
>>> Changelog:
>>> v4:
>>> - fixed broken conditional compilation and adjusted comments in dwc2_hsotg
>>> structure documentation
>>>
>>> v3:
>>> - rebased onto latest 'testing/next' from Felipe Balbi (includes
>>> s3c_hsotg -> dwc2 rename)
>>>
>>> v2:
>>> - moved setting of ll_hw_enabled flag to enable/disable functions,
>>> as suggested by John Youn
>>> - moved setting of phy width to dwc2_lowlevel_init function
>>> ---
>>> drivers/usb/dwc2/core.h | 24 +++--
>>> drivers/usb/dwc2/gadget.c | 193 ++++--------------------------------
>>> drivers/usb/dwc2/platform.c | 234 +++++++++++++++++++++++++++++++++++++-------
>>> 3 files changed, 228 insertions(+), 223 deletions(-)
>>>
>> Hi Marek,
>>
>> I still see lockdep warnings.
>>
>> Any ideas about these?
>>
>>
>> [ 1618.179611] ======================================================
>> [ 1618.179612] [ INFO: possible circular locking dependency detected ]
>> [ 1618.179613] 4.3.0-rc3-snps-00125-g744fd93 #28 Not tainted
>> [ 1618.179614] -------------------------------------------------------
>> [ 1618.179615] modprobe/2658 is trying to acquire lock:
>> [ 1618.179616] (&hsotg->init_mutex){+.+.+.}, at: [<ffffffffc043aa3c>] dwc2_hsotg_udc_start+0x5c/0x200 [dwc2]
>> [ 1618.179622]
>> [ 1618.179622] but task is already holding lock:
>> [ 1618.179623] (udc_lock){+.+.+.}, at: [<ffffffffc0374b8a>] usb_gadget_probe_driver+0x3a/0xd0 [udc_core]
>> [ 1618.179627]
>> [ 1618.179627] which lock already depends on the new lock.
>> [ 1618.179627]
>> [ 1618.179628]
>> [ 1618.179628] the existing dependency chain (in reverse order) is:
>> [ 1618.179629]
>> [ 1618.179629] -> #1 (udc_lock){+.+.+.}:
>> [ 1618.179631] [<ffffffff810da56d>] lock_acquire+0xdd/0x1f0
>> [ 1618.179635] [<ffffffff818658a6>] mutex_lock_nested+0x76/0x3e0
>> [ 1618.179638] [<ffffffffc0374da7>] usb_add_gadget_udc_release+0x187/0x240 [udc_core]
>> [ 1618.179640] [<ffffffffc0374e70>] usb_add_gadget_udc+0x10/0x20 [udc_core]
>> [ 1618.179642] [<ffffffffc043b30c>] dwc2_gadget_init+0x47c/0x580 [dwc2]
>> [ 1618.179645] [<ffffffffc042d2f2>] dwc2_driver_probe+0x422/0x4b0 [dwc2]
>> [ 1618.179648] [<ffffffff8153fe94>] platform_drv_probe+0x34/0x90
>> [ 1618.179650] [<ffffffff8153db54>] driver_probe_device+0x224/0x480
>> [ 1618.179652] [<ffffffff8153deb1>] __device_attach_driver+0x71/0xa0
>> [ 1618.179654] [<ffffffff8153b78d>] bus_for_each_drv+0x5d/0x90
>> [ 1618.179655] [<ffffffff8153d83f>] __device_attach+0xbf/0x140
>> [ 1618.179657] [<ffffffff8153df23>] device_initial_probe+0x13/0x20
>> [ 1618.179658] [<ffffffff8153cb03>] bus_probe_device+0xa3/0xb0
>> [ 1618.179660] [<ffffffff8153a76d>] device_add+0x40d/0x690
>> [ 1618.179661] [<ffffffff8153fb81>] platform_device_add+0x111/0x270
>> [ 1618.179663] [<ffffffffc0394128>] dwc2_pci_probe+0xe8/0x1d2 [dwc2_pci]
>> [ 1618.179665] [<ffffffff81446085>] local_pci_probe+0x45/0xa0
>> [ 1618.179668] [<ffffffff81447451>] pci_device_probe+0xe1/0x130
>> [ 1618.179669] [<ffffffff8153db54>] driver_probe_device+0x224/0x480
>> [ 1618.179671] [<ffffffff8153de38>] __driver_attach+0x88/0x90
>> [ 1618.179672] [<ffffffff8153b6d6>] bus_for_each_dev+0x66/0xa0
>> [ 1618.179674] [<ffffffff8153d31e>] driver_attach+0x1e/0x20
>> [ 1618.179675] [<ffffffff8153ce8e>] bus_add_driver+0x1ee/0x280
>> [ 1618.179677] [<ffffffff8153e930>] driver_register+0x60/0xe0
>> [ 1618.179678] [<ffffffff81445a60>] __pci_register_driver+0x60/0x70
>> [ 1618.179680] [<ffffffffc000601e>] 0xffffffffc000601e
>> [ 1618.179681] [<ffffffff81002123>] do_one_initcall+0xb3/0x200
>> [ 1618.179684] [<ffffffff811a8a41>] do_init_module+0x5f/0x1e7
>> [ 1618.179687] [<ffffffff81120e48>] load_module+0x21a8/0x2840
>> [ 1618.179689] [<ffffffff8112170a>] SyS_finit_module+0x9a/0xc0
>> [ 1618.179691] [<ffffffff81869c36>] entry_SYSCALL_64_fastpath+0x16/0x7a
>> [ 1618.179693]
>> [ 1618.179693] -> #0 (&hsotg->init_mutex){+.+.+.}:
>> [ 1618.179695] [<ffffffff810d97f5>] __lock_acquire+0x1d35/0x1db0
>> [ 1618.179697] [<ffffffff810da56d>] lock_acquire+0xdd/0x1f0
>> [ 1618.179698] [<ffffffff818658a6>] mutex_lock_nested+0x76/0x3e0
>> [ 1618.179700] [<ffffffffc043aa3c>] dwc2_hsotg_udc_start+0x5c/0x200 [dwc2]
>> [ 1618.179703] [<ffffffffc0374a34>] udc_bind_to_driver+0xa4/0x100 [udc_core]
>> [ 1618.179705] [<ffffffffc0374bca>] usb_gadget_probe_driver+0x7a/0xd0 [udc_core]
>> [ 1618.179707] [<ffffffffc059a674>] usb_composite_probe+0xa4/0xc0 [libcomposite]
>> [ 1618.179709] [<ffffffffc0474010>] msg_init+0x10/0x1000 [g_mass_storage]
>> [ 1618.179711] [<ffffffff81002123>] do_one_initcall+0xb3/0x200
>> [ 1618.179713] [<ffffffff811a8a41>] do_init_module+0x5f/0x1e7
>> [ 1618.179714] [<ffffffff81120e48>] load_module+0x21a8/0x2840
>> [ 1618.179716] [<ffffffff8112170a>] SyS_finit_module+0x9a/0xc0
>> [ 1618.179717] [<ffffffff81869c36>] entry_SYSCALL_64_fastpath+0x16/0x7a
>> [ 1618.179719]
>> [ 1618.179719] other info that might help us debug this:
>> [ 1618.179719]
>> [ 1618.179720] Possible unsafe locking scenario:
>> [ 1618.179720]
>> [ 1618.179721] CPU0 CPU1
>> [ 1618.179722] ---- ----
>> [ 1618.179722] lock(udc_lock);
>> [ 1618.179723] lock(&hsotg->init_mutex);
> It seems like init_mutex is completely unnecessary in this driver. In
> fact, why are you trying to hold a mutex while inside a spinlock ?
init_mutex is a leftover from the time, when s3c-hsotg driver didn't
implement
proper pull up/down control and emulated it by enabling disabling phy.
It can
be removed now. btw, the possible lockup pointed by John is an
interaction of
two mutexes, not a case of taking mutex under a spinlock.
I will send an updated patch in a few minutes.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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