Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Hi Alexander,

Am Montag, 15. Mai 2023, 14:04:10 CEST schrieb Sverdlin, Alexander:
> Hello Alexander!
> 
> On Mon, 2023-05-15 at 11:11 +0200, Alexander Stein wrote:
> 
> > > [   22.503179] other info that might help us debug this:
> > > [   22.503179]
> > > [   22.503183] Chain exists of:
> > > [   22.503183]   prepare_lock --> rtc_pcf85063:594:(&config-
> > > 
> > > >regmap)->lock
> > > 
> > > --> i2c_register_adapter
> > > [   22.503183]
> > > [   22.503207]  Possible unsafe locking scenario:
> > > [   22.503207]
> > > [   22.503210]        CPU0                    CPU1
> > > [   22.503213]        ----                    ----
> > > [   22.503216]   lock(i2c_register_adapter);
> > > [   22.503225]                               
> > > lock(rtc_pcf85063:594:(&config-
> > > 
> > > > regmap)->lock);
> > > 
> > > 
> > > [   22.503235]                               
> > > lock(i2c_register_adapter);
> > > [   22.503244]   lock(prepare_lock);
> > > [   22.503253]
> > > [   22.503253]  *** DEADLOCK ***
> > > 
> > > Now lpi2c_runtime_resume will call into clk_prepare() which also
> > > calls
> > > clk_prepare_lock() (identical to clk_get_rate).
> > > 
> > > Best regards,
> > > Alexader
> > > 
> > > 
> > > >         pm_runtime_set_autosuspend_delay(&pdev->dev,
> > > > I2C_PM_TIMEOUT);
> > > >         pm_runtime_use_autosuspend(&pdev->dev);
> > > >         pm_runtime_get_noresume(&pdev->dev);
> > 
> > 
> > With commit fa39065833db ("i2c: imx-lpi2c: avoid taking clk_prepare
> > mutex in 
> > PM callbacks") in place, the additional deadlock warning regarding
> > runtime 
> > resume is gone.
> > So only the ordering issue needs to be addressed.
> 
> 
> Unfortunately with both your (backported) and my patches applied I've
> got a 3rd warning:
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.15.71+git8e43aee #1 Tainted: G           O     
> ------------------------------------------------------
> xxxxxxx/2238 is trying to acquire lock:
> ffff0000040bda40 (&desc->request_mutex){+.+.}-{3:3}, at:
> __setup_irq+0xbc/0x8bc
> 
> but task is already holding lock:
> ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus+0x2c/0x3c
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #5 (i2c_register_adapter){+.+.}-{3:3}:
>        lock_acquire+0x68/0x84
>        rt_mutex_lock_nested+0x88/0xe0
>        i2c_adapter_lock_bus+0x2c/0x3c
>        i2c_transfer+0x58/0x130
>        regmap_i2c_read+0x64/0xb0
>        _regmap_raw_read+0x114/0x440
>        _regmap_bus_read+0x4c/0x84
>        _regmap_read+0x6c/0x270
>        regmap_read+0x54/0x80
>        pcf85063_probe+0xec/0x4cc
>        i2c_device_probe+0x10c/0x350
>        really_probe+0xc4/0x470
>        __driver_probe_device+0x11c/0x190
>        driver_probe_device+0x48/0x110
>        __device_attach_driver+0xc4/0x160
>        bus_for_each_drv+0x80/0xe0
>        __device_attach+0xb0/0x1f0
>        device_initial_probe+0x1c/0x2c
>        bus_probe_device+0xa4/0xb0
>        device_add+0x398/0x8ac
>        device_register+0x28/0x40
>        i2c_new_client_device+0x144/0x290
>        of_i2c_register_devices+0x18c/0x230
>        i2c_register_adapter+0x1dc/0x6b0
>        __i2c_add_numbered_adapter+0x68/0xbc
>        i2c_add_adapter+0xb0/0xe0
>        lpi2c_imx_probe+0x3a4/0x670
>        platform_probe+0x70/0xec
>        really_probe+0xc4/0x470
>        __driver_probe_device+0x11c/0x190
>        driver_probe_device+0x48/0x110
>        __device_attach_driver+0xc4/0x160
>        bus_for_each_drv+0x80/0xe0
>        __device_attach+0xb0/0x1f0
>        device_initial_probe+0x1c/0x2c
>        bus_probe_device+0xa4/0xb0
>        deferred_probe_work_func+0xb8/0x110
>        process_one_work+0x27c/0x6c4
>        worker_thread+0x7c/0x450
>        kthread+0x168/0x17c
>        ret_from_fork+0x10/0x20
> 
> -> #4 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
>        lock_acquire+0x68/0x84
>        __mutex_lock+0xa8/0x4d0
>        mutex_lock_nested+0x48/0x54
>        regmap_lock_mutex+0x1c/0x30
>        regmap_read+0x44/0x80
>        pcf85063_clkout_recalc_rate+0x34/0x80
>        __clk_register+0x520/0x880
>        devm_clk_register+0x64/0xc4
>        pcf85063_probe+0x24c/0x4cc
>        i2c_device_probe+0x10c/0x350
>        really_probe+0xc4/0x470
>        __driver_probe_device+0x11c/0x190
>        driver_probe_device+0x48/0x110
>        __device_attach_driver+0xc4/0x160
>        bus_for_each_drv+0x80/0xe0
>        __device_attach+0xb0/0x1f0
>        device_initial_probe+0x1c/0x2c
>        bus_probe_device+0xa4/0xb0
>        device_add+0x398/0x8ac
>        device_register+0x28/0x40
>        i2c_new_client_device+0x144/0x290
>        of_i2c_register_devices+0x18c/0x230
>        i2c_register_adapter+0x1dc/0x6b0
>        __i2c_add_numbered_adapter+0x68/0xbc
>        i2c_add_adapter+0xb0/0xe0
>        lpi2c_imx_probe+0x3a4/0x670
>        platform_probe+0x70/0xec
>        really_probe+0xc4/0x470
>        __driver_probe_device+0x11c/0x190
>        driver_probe_device+0x48/0x110
>        __device_attach_driver+0xc4/0x160
>        bus_for_each_drv+0x80/0xe0
>        __device_attach+0xb0/0x1f0
>        device_initial_probe+0x1c/0x2c
>        bus_probe_device+0xa4/0xb0
>        deferred_probe_work_func+0xb8/0x110
>        process_one_work+0x27c/0x6c4
>        worker_thread+0x7c/0x450
>        kthread+0x168/0x17c
>        ret_from_fork+0x10/0x20
> 
> -> #3 (prepare_lock){+.+.}-{3:3}:
>        lock_acquire+0x68/0x84
>        __mutex_lock+0xa8/0x4d0
>        mutex_lock_nested+0x48/0x54
>        clk_prepare_lock+0x50/0xb0
>        clk_prepare+0x28/0x50
>        fec_runtime_resume+0x3c/0xe0
>        pm_generic_runtime_resume+0x34/0x50
>        __genpd_runtime_resume+0x38/0x90
>        genpd_runtime_resume+0xa0/0x304
>        __rpm_callback+0x50/0x1b0
>        rpm_callback+0x40/0x80
>        rpm_resume+0x448/0x6e0
>        __pm_runtime_resume+0x50/0xc0
>        fec_enet_mdio_read+0x48/0x190
>        __mdiobus_read+0x48/0xb0
>        mdiobus_read_nested+0x48/0x70
>        mv88e6xxx_smi_dual_direct_read+0x2c/0x50
>        mv88e6xxx_read+0x64/0xf0
>        mv88e6xxx_g1_read+0x28/0x34
>        mv88e6xxx_g1_irq_thread_work+0x50/0x17c
>        mv88e6xxx_irq_poll+0x28/0x50
>        kthread_worker_fn+0x100/0x480
>        kthread+0x168/0x17c
>        ret_from_fork+0x10/0x20
> 
> -> #2 (&bus->mdio_lock/2){+.+.}-{3:3}:
>        lock_acquire+0x68/0x84
>        __mutex_lock+0xa8/0x4d0
>        mutex_lock_nested+0x48/0x54
>        mdiobus_read_nested+0x38/0x70
>        mv88e6xxx_smi_dual_direct_read+0x2c/0x50
>        mv88e6xxx_read+0x64/0xf0
>        mv88e6xxx_port_read+0x24/0x30
>        mv88e6xxx_probe+0x250/0x7f0
>        mdio_probe+0x3c/0x80
>        really_probe+0xc4/0x470
>        __driver_probe_device+0x11c/0x190
>        driver_probe_device+0x48/0x110
>        __device_attach_driver+0xc4/0x160
>        bus_for_each_drv+0x80/0xe0
>        __device_attach+0xb0/0x1f0
>        device_initial_probe+0x1c/0x2c
>        bus_probe_device+0xa4/0xb0
>        deferred_probe_work_func+0xb8/0x110
>        process_one_work+0x27c/0x6c4
>        worker_thread+0x7c/0x450
>        kthread+0x168/0x17c
>        ret_from_fork+0x10/0x20
> 
> -> #1 (&chip->reg_lock){+.+.}-{3:3}:
>        lock_acquire+0x68/0x84
>        __mutex_lock+0xa8/0x4d0
>        mutex_lock_nested+0x48/0x54
>        mv88e6xxx_g1_irq_bus_lock+0x24/0x30
>        __setup_irq+0x6e0/0x8bc
>        request_threaded_irq+0xf4/0x1b4
>        mv88e6xxx_g2_irq_setup+0x1f0/0x2b4
>        mv88e6xxx_probe+0x480/0x7f0
>        mdio_probe+0x3c/0x80
>        really_probe+0xc4/0x470
>        __driver_probe_device+0x11c/0x190
>        driver_probe_device+0x48/0x110
>        __device_attach_driver+0xc4/0x160
>        bus_for_each_drv+0x80/0xe0
>        __device_attach+0xb0/0x1f0
>        device_initial_probe+0x1c/0x2c
>        bus_probe_device+0xa4/0xb0
>        deferred_probe_work_func+0xb8/0x110
>        process_one_work+0x27c/0x6c4
>        worker_thread+0x7c/0x450
>        kthread+0x168/0x17c
>        ret_from_fork+0x10/0x20
> 
> -> #0 (&desc->request_mutex){+.+.}-{3:3}:
>        __lock_acquire+0x12a4/0x20a0
>        lock_acquire.part.0+0xe0/0x230
>        lock_acquire+0x68/0x84
>        __mutex_lock+0xa8/0x4d0
>        mutex_lock_nested+0x48/0x54
>        __setup_irq+0xbc/0x8bc
>        request_threaded_irq+0xf4/0x1b4
>        devm_request_threaded_irq+0x88/0x104
>        lpi2c_runtime_resume+0x70/0xe4

This looks like the NXP downstream kernel, requesting the IRQ from within 
runtime resume.

>        pm_generic_runtime_resume+0x34/0x50
>        __genpd_runtime_resume+0x38/0x90
>        genpd_runtime_resume+0xa0/0x304
>        __rpm_callback+0x50/0x1b0
>        rpm_callback+0x74/0x80
>        rpm_resume+0x448/0x6e0
>        __pm_runtime_resume+0x50/0xc0
>        lpi2c_imx_xfer+0x60/0xa5c
>        __i2c_transfer+0x174/0xa80
>        i2c_transfer+0x68/0x130
>        regmap_i2c_read+0x64/0xb0
>        _regmap_raw_read+0x114/0x440
>        regmap_raw_read+0x19c/0x28c
>        regmap_bulk_read+0x1b8/0x244
>        at24_read+0x14c/0x2c4
>        nvmem_reg_read+0x2c/0x54
>        bin_attr_nvmem_read+0x8c/0xbc
>        sysfs_kf_bin_read+0x74/0x94
>        kernfs_fop_read_iter+0xb0/0x1d0
>        new_sync_read+0xf0/0x184
>        vfs_read+0x154/0x1f0
>        ksys_read+0x70/0x100
>        __arm64_sys_read+0x24/0x30
>        invoke_syscall+0x50/0x120
>        el0_svc_common.constprop.0+0x68/0x124
>        do_el0_svc+0x30/0x9c
>        el0_svc+0x54/0x110
>        el0t_64_sync_handler+0xa4/0x130
>        el0t_64_sync+0x1a0/0x1a4
> 
> other info that might help us debug this:
> 
> Chain exists of:
>   &desc->request_mutex --> rtc_pcf85063:560:(&config->regmap)->lock -->
> i2c_register_adapter
> 
>  Possible unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(i2c_register_adapter);
>                                lock(rtc_pcf85063:560:(&config->regmap)-
> 
> >lock);
> 
>                                lock(i2c_register_adapter);
>   lock(&desc->request_mutex);
> 
>  *** DEADLOCK ***
> 
> 4 locks held by xxxxxxx/2238:
>  #0: ffff000015a64488 (&of->mutex){+.+.}-{3:3}, at:
> kernfs_fop_read_iter+0x74/0x1d0
>  #1: ffff0000119e2400 (kn->active#58){.+.+}-{0:0}, at:
> kernfs_fop_read_iter+0x7c/0x1d0
>  #2: ffff0000119a26e8 (&at24->lock){+.+.}-{3:3}, at:
> at24_read+0x8c/0x2c4
>  #3: ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus+0x2c/0x3c
> 
> stack backtrace:
> CPU: 1 PID: 2238 Comm: xxxxxxx Tainted: G           O     
> 5.15.71+git8e43aee #1
> Hardware name: Siemens PXC5.E24 (DT)
> Call trace:
>  dump_backtrace+0x0/0x1d4
>  show_stack+0x20/0x2c
>  dump_stack_lvl+0x8c/0xb8
>  dump_stack+0x18/0x34
>  print_circular_bug+0x1f8/0x200
>  check_noncircular+0x130/0x144
>  __lock_acquire+0x12a4/0x20a0
>  lock_acquire.part.0+0xe0/0x230
>  lock_acquire+0x68/0x84
>  __mutex_lock+0xa8/0x4d0
>  mutex_lock_nested+0x48/0x54
>  __setup_irq+0xbc/0x8bc
>  request_threaded_irq+0xf4/0x1b4
>  devm_request_threaded_irq+0x88/0x104
>  lpi2c_runtime_resume+0x70/0xe4

It seems your (possible) deadlock is triggered along devm_request_irq() during 
resume.
As mainline just enables the clocks, there is nothing we can do here. Your 
patch still is sensible, can you send a new version with the review addressed? 
Thanks.

Best regards,
Alexander

>  pm_generic_runtime_resume+0x34/0x50
>  __genpd_runtime_resume+0x38/0x90
>  genpd_runtime_resume+0xa0/0x304
>  __rpm_callback+0x50/0x1b0
>  rpm_callback+0x74/0x80
>  rpm_resume+0x448/0x6e0
>  __pm_runtime_resume+0x50/0xc0
>  lpi2c_imx_xfer+0x60/0xa5c
>  __i2c_transfer+0x174/0xa80
>  i2c_transfer+0x68/0x130
>  regmap_i2c_read+0x64/0xb0
>  _regmap_raw_read+0x114/0x440
>  regmap_raw_read+0x19c/0x28c
>  regmap_bulk_read+0x1b8/0x244
>  at24_read+0x14c/0x2c4
>  nvmem_reg_read+0x2c/0x54
>  bin_attr_nvmem_read+0x8c/0xbc
>  sysfs_kf_bin_read+0x74/0x94
>  kernfs_fop_read_iter+0xb0/0x1d0
>  new_sync_read+0xf0/0x184
>  vfs_read+0x154/0x1f0
>  ksys_read+0x70/0x100
>  __arm64_sys_read+0x24/0x30
>  invoke_syscall+0x50/0x120
>  el0_svc_common.constprop.0+0x68/0x124
>  do_el0_svc+0x30/0x9c
>  el0_svc+0x54/0x110
>  el0t_64_sync_handler+0xa4/0x130
>  el0t_64_sync+0x1a0/0x1a4
> 
> So this doesn't look like an end of the story yet, unfortunately.
> 
> -- 
> Alexander Sverdlin
> Siemens AG
> www.siemens.com


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