[REGRESSION] Re: [PATCH v2] net: fec: Use a spinlock to guard `fep->ptp_clk_on`

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Sep 01, 2022 at 04:04:03PM +0200, Csókás Bence wrote:
> Mutexes cannot be taken in a non-preemptible context,
> causing a panic in `fec_ptp_save_state()`. Replacing
> `ptp_clk_mutex` by `tmreg_lock` fixes this.
> 
> Fixes: 6a4d7234ae9a ("net: fec: ptp: avoid register access when ipg clock is disabled")
> Fixes: f79959220fa5 ("fec: Restart PPS after link state change")
> Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
> Link: https://lore.kernel.org/all/20220827160922.642zlcd5foopozru@pengutronix.de/
> Signed-off-by: Csókás Bence <csokas.bence@prolan.hu>

For regzbot:

This patch results in the following backtrace.

[   18.401688] BUG: sleeping function called from invalid context at drivers/clk/imx/clk-pllv3.c:68
[   18.402277] in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 1, name: swapper/0
[   18.402531] preempt_count: 1, expected: 0
[   18.402781] 3 locks held by swapper/0/1:
[   18.402967]  #0: c423ac8c (&dev->mutex){....}-{3:3}, at: __driver_attach+0x80/0x158
[   18.404364]  #1: c40dc8e8 (&fep->tmreg_lock){....}-{2:2}, at: fec_enet_clk_enable+0x58/0x250
[   18.404752]  #2: c1a71af8 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0xc/0xd4
[   18.405246] irq event stamp: 129384
[   18.405403] hardirqs last  enabled at (129383): [<c10850b0>] _raw_spin_unlock_irqrestore+0x50/0x64
[   18.405667] hardirqs last disabled at (129384): [<c1084e70>] _raw_spin_lock_irqsave+0x64/0x68
[   18.405915] softirqs last  enabled at (129218): [<c01017bc>] __do_softirq+0x2ac/0x604
[   18.406255] softirqs last disabled at (129209): [<c012eee4>] __irq_exit_rcu+0x138/0x17c
[   18.406792] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G                 N 6.0.0-rc5 #1
[   18.407131] Hardware name: Freescale i.MX7 Dual (Device Tree)
[   18.407590]  unwind_backtrace from show_stack+0x10/0x14
[   18.407890]  show_stack from dump_stack_lvl+0x68/0x90
[   18.408097]  dump_stack_lvl from __might_resched+0x17c/0x284
[   18.408328]  __might_resched from clk_pllv3_wait_lock+0x4c/0xcc
[   18.408557]  clk_pllv3_wait_lock from clk_core_prepare+0xc4/0x328
[   18.408783]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.408986]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.409205]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.409416]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.409631]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.409847]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.410065]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.410284]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.410513]  clk_core_prepare from clk_core_prepare+0x50/0x328
[   18.410729]  clk_core_prepare from clk_prepare+0x20/0x30
[   18.410936]  clk_prepare from fec_enet_clk_enable+0x68/0x250
[   18.411143]  fec_enet_clk_enable from fec_probe+0x32c/0x1430
[   18.411352]  fec_probe from platform_probe+0x58/0xbc
[   18.411558]  platform_probe from really_probe+0xc4/0x2f4
[   18.411772]  really_probe from __driver_probe_device+0x80/0xe4
[   18.411983]  __driver_probe_device from driver_probe_device+0x2c/0xc4
[   18.412203]  driver_probe_device from __driver_attach+0x8c/0x158
[   18.412418]  __driver_attach from bus_for_each_dev+0x74/0xc0
[   18.412631]  bus_for_each_dev from bus_add_driver+0x154/0x1e8
[   18.412844]  bus_add_driver from driver_register+0x88/0x11c
[   18.413055]  driver_register from do_one_initcall+0x68/0x428
[   18.413271]  do_one_initcall from kernel_init_freeable+0x18c/0x240
[   18.413502]  kernel_init_freeable from kernel_init+0x14/0x144
[   18.413721]  kernel_init from ret_from_fork+0x14/0x28
[   18.414036] Exception stack(0xd0825fb0 to 0xd0825ff8)
[   18.414523] 5fa0:                                     00000000 00000000 00000000 00000000
[   18.414792] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[   18.415032] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000