netdev - [PATCH v2 net] ptp_qoriq: Initialize the registers' spinlock before calling ptp_qoriq

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Date:   Tue,  1 Oct 2019 22:07:01 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     richardcochran@...il.com, yangbo.lu@....com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, Vladimir Oltean <olteanv@...il.com>
Subject: [PATCH v2 net] ptp_qoriq: Initialize the registers' spinlock before calling ptp_qoriq_settime

Because ptp_qoriq_settime is being called prior to spin_lock_init, the
following stack trace can be seen at driver probe time:

[    2.269117] the code is fine but needs lockdep annotation.
[    2.274569] turning off the locking correctness validator.
[    2.280027] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.3.0-rc7-01478-g01eaa67a4797 #263
[    2.288073] Hardware name: Freescale LS1021A
[    2.292337] [<c0313cb4>] (unwind_backtrace) from [<c030e11c>] (show_stack+0x10/0x14)
[    2.300045] [<c030e11c>] (show_stack) from [<c1219440>] (dump_stack+0xcc/0xf8)
[    2.307235] [<c1219440>] (dump_stack) from [<c03b9b44>] (register_lock_class+0x730/0x73c)
[    2.315372] [<c03b9b44>] (register_lock_class) from [<c03b6190>] (__lock_acquire+0x78/0x270c)
[    2.323856] [<c03b6190>] (__lock_acquire) from [<c03b90cc>] (lock_acquire+0xe0/0x22c)
[    2.331649] [<c03b90cc>] (lock_acquire) from [<c123c310>] (_raw_spin_lock_irqsave+0x54/0x68)
[    2.340048] [<c123c310>] (_raw_spin_lock_irqsave) from [<c0e73fe4>] (ptp_qoriq_settime+0x38/0x80)
[    2.348878] [<c0e73fe4>] (ptp_qoriq_settime) from [<c0e746d4>] (ptp_qoriq_init+0x1f8/0x484)
[    2.357189] [<c0e746d4>] (ptp_qoriq_init) from [<c0e74aac>] (ptp_qoriq_probe+0xd0/0x184)
[    2.365243] [<c0e74aac>] (ptp_qoriq_probe) from [<c0b0a07c>] (platform_drv_probe+0x48/0x9c)
[    2.373555] [<c0b0a07c>] (platform_drv_probe) from [<c0b07a14>] (really_probe+0x1c4/0x400)
[    2.381779] [<c0b07a14>] (really_probe) from [<c0b07e28>] (driver_probe_device+0x78/0x1b8)
[    2.390003] [<c0b07e28>] (driver_probe_device) from [<c0b081d0>] (device_driver_attach+0x58/0x60)
[    2.398832] [<c0b081d0>] (device_driver_attach) from [<c0b082d4>] (__driver_attach+0xfc/0x160)
[    2.407402] [<c0b082d4>] (__driver_attach) from [<c0b05a84>] (bus_for_each_dev+0x68/0xb4)
[    2.415539] [<c0b05a84>] (bus_for_each_dev) from [<c0b06b68>] (bus_add_driver+0x104/0x20c)
[    2.423763] [<c0b06b68>] (bus_add_driver) from [<c0b0909c>] (driver_register+0x78/0x10c)
[    2.431815] [<c0b0909c>] (driver_register) from [<c030313c>] (do_one_initcall+0x8c/0x3ac)
[    2.439954] [<c030313c>] (do_one_initcall) from [<c1f013f4>] (kernel_init_freeable+0x468/0x548)
[    2.448610] [<c1f013f4>] (kernel_init_freeable) from [<c12344d8>] (kernel_init+0x8/0x10c)
[    2.456745] [<c12344d8>] (kernel_init) from [<c03010b4>] (ret_from_fork+0x14/0x20)
[    2.464273] Exception stack(0xea89ffb0 to 0xea89fff8)
[    2.469297] ffa0:                                     00000000 00000000 00000000 00000000
[    2.477432] ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    2.485566] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000

Fixes: ff54571a747b ("ptp_qoriq: convert to use ptp_qoriq_init/free")
Signed-off-by: Vladimir Oltean <olteanv@...il.com>
---
Changes in v2:
- Followed Richard Cochran's feedback:

	Please fix the actual bug, the spin lock issue, and don't worry about
	changing the initial value.

 drivers/ptp/ptp_qoriq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/ptp/ptp_qoriq.c b/drivers/ptp/ptp_qoriq.c
index c61f00b72e15..a577218d1ab7 100644
--- a/drivers/ptp/ptp_qoriq.c
+++ b/drivers/ptp/ptp_qoriq.c
@@ -507,6 +507,8 @@ int ptp_qoriq_init(struct ptp_qoriq *ptp_qoriq, void __iomem *base,
 		ptp_qoriq->regs.etts_regs = base + ETTS_REGS_OFFSET;
 	}
 
+	spin_lock_init(&ptp_qoriq->lock);
+
 	ktime_get_real_ts64(&now);
 	ptp_qoriq_settime(&ptp_qoriq->caps, &now);
 
@@ -514,7 +516,6 @@ int ptp_qoriq_init(struct ptp_qoriq *ptp_qoriq, void __iomem *base,
 	  (ptp_qoriq->tclk_period & TCLK_PERIOD_MASK) << TCLK_PERIOD_SHIFT |
 	  (ptp_qoriq->cksel & CKSEL_MASK) << CKSEL_SHIFT;
 
-	spin_lock_init(&ptp_qoriq->lock);
 	spin_lock_irqsave(&ptp_qoriq->lock, flags);
 
 	regs = &ptp_qoriq->regs;
-- 
2.17.1