Help: i.MX8MP AUDIOMIX BLK-CTRL CLK driver support

[Peng Fan]

Hi All,

I would start a discussion about the A/B B/A lock issue when make 
audiomix blk ctrl function as clk provider.

I not have good idea on this, hope you have any suggestions.

major issue is: the blk ctrl clk has a power domain supplier
The power domain supplier also use clk API to prepare_enable clks.
The blk ctrl clk driver has runtime pm enabled.

The NXP downstream:
The dts:
https://github.com/nxp-imx/linux-imx/blob/lf-5.15.y/arch/arm64/boot/dts/freescale/imx8mp.dtsi#L1872

The driver:
https://github.com/nxp-imx/linux-imx/blob/lf-5.15.y/drivers/clk/imx/clk-imx8mp.c
https://github.com/nxp-imx/linux-imx/blob/lf-5.15.y/drivers/clk/imx/clk-blk-ctrl.c

Note: The following log was reproduced with NXP downstream. For upstream
I think we have similar issue if we still take audiomix blk ctrl as clk
driver. Because the gpcv2 also use clk prepare enable API.
1. deadlock 1:
Callchain after enable some lock debug:
clk_ignore_unused will use lock seq: take prepare lock, take blk-ctrl 
parent power domain genpd lock
genpd_power_off_work_fun will use lock seq: take the power domain genpd 
lock, take prepare lock.

clk_disable_unused:
[   11.667711][  T108] -> #1 (&genpd->mlock){+.+.}-{3:3}:
[   11.675041][  T108]        __lock_acquire+0xae4/0xef8
[   11.680093][  T108]        lock_acquire+0xfc/0x2f8
[   11.684888][  T108]        __mutex_lock+0x90/0x870
[   11.689685][  T108]        mutex_lock_nested+0x44/0x50
[   11.694826][  T108]        genpd_lock_mtx+0x18/0x24
[   11.699706][  T108]        genpd_runtime_resume+0x90/0x214 (hold 
genpd->mlock)
[   11.705194][  T108]        __rpm_callback+0x80/0x2c0
[   11.710160][  T108]        rpm_resume+0x468/0x650
[   11.714866][  T108]        __pm_runtime_resume+0x60/0x88
[   11.720180][  T108]        clk_pm_runtime_get+0x28/0x9c
[   11.725410][  T108]        clk_disable_unused_subtree+0x8c/0x144
[   11.731420][  T108]        clk_disable_unused_subtree+0x124/0x144
[   11.737518][  T108]        clk_disable_unused+0xa4/0x11c (hold 
prepare_lock)
[   11.742833][  T108]        do_one_initcall+0x98/0x178
[   11.747888][  T108]        do_initcall_level+0x9c/0xb8
[   11.753028][  T108]        do_initcalls+0x54/0x94
[   11.757736][  T108]        do_basic_setup+0x24/0x30
[   11.762614][  T108]        kernel_init_freeable+0x70/0xa4
[   11.768014][  T108]        kernel_init+0x14/0x18c
[   11.772722][  T108]        ret_from_fork+0x10/0x18
[   11.777512][  T108] -> #0 (prepare_lock){+.+.}-{3:3}:
[   11.784749][  T108]        check_noncircular+0x134/0x13c
[   11.790064][  T108]        validate_chain+0x590/0x2a04
[   11.795204][  T108]        __lock_acquire+0xae4/0xef8
[   11.800258][  T108]        lock_acquire+0xfc/0x2f8
[   11.805050][  T108]        __mutex_lock+0x90/0x870
[   11.809841][  T108]        mutex_lock_nested+0x44/0x50
[   11.814983][  T108]        clk_unprepare+0x5c/0x100 ((hold prepare_lock))
[   11.819864][  T108]        imx8m_pd_power_off+0xac/0x110
[   11.825179][  T108]        genpd_power_off+0x1b4/0x2dc
[   11.830318][  T108]        genpd_power_off_work_fn+0x38/0x58 (hold 
genpd->mlock)
[   11.835981][  T108]        process_one_work+0x270/0x444
[   11.841208][  T108]        worker_thread+0x280/0x4e4
[   11.846176][  T108]        kthread+0x13c/0x14c
[   11.850621][  T108]        ret_from_fork+0x10/0x18


2:
another mutex dead lock between deferred_probe_work_func/ 
genpd_power_off_work_fn

The sequency in deferred_probe_work_func is lock the clk firstly, than 
hold pd secondly.


[   11.351159][   T46] the existing dependency chain (in reverse order) is:
[   11.351162][   T46]
[   11.351162][   T46] -> #1 (&genpd->mlock){+.+.}-{3:3}:
[   11.351176][   T46]        __lock_acquire+0xae4/0xef8
[   11.351180][   T46]        lock_acquire+0xfc/0x2f8
[   11.351185][   T46]        __mutex_lock+0x90/0x870
[   11.351188][   T46]        mutex_lock_nested+0x44/0x50
[   11.351192][   T46]        genpd_lock_mtx+0x18/0x24
[   11.351196][   T46]        genpd_runtime_suspend+0x1dc/0x224 (hold pd 
lock)
[   11.351201][   T46]        __rpm_callback+0x80/0x2c0
[   11.351205][   T46]        rpm_suspend+0x2a4/0x62c
[   11.351208][   T46]        rpm_idle+0x158/0x228
[   11.351212][   T46]        __pm_runtime_idle+0x64/0xac
[   11.351217][   T46]        clk_change_rate+0x400/0x494 
(clk_pm_runtime_put()
[   11.351220][   T46]        clk_change_rate+0x438/0x494
[   11.351224][   T46]        clk_core_set_rate_nolock+0x22c/0x2d8
[   11.351228][   T46]        clk_set_rate+0x94/0x134 (hold prepared lock)
[   11.351232][   T46]        of_clk_set_defaults+0x27c/0x364
[   11.351236][   T46]        platform_drv_probe+0x28/0xbc
[   11.351241][   T46]        really_probe+0x1dc/0x4c0
[   11.351245][   T46]        driver_probe_device+0x7c/0xb8
[   11.351249][   T46]        __device_attach_driver+0x118/0x13c
[   11.351253][   T46]        bus_for_each_drv+0x80/0xcc
[   11.351257][   T46]        __device_attach+0xd0/0x174
[   11.351261][   T46]        device_initial_probe+0x14/0x20
[   11.351265][   T46]        bus_probe_device+0x34/0x9c
[   11.351269][   T46]        deferred_probe_work_func+0x64/0xc4
[   11.351274][   T46]        process_one_work+0x270/0x444
[   11.351278][   T46]        worker_thread+0x280/0x4e4
[   11.351288][   T46]        kthread+0x13c/0x14c
[   11.529876][   T46]        ret_from_fork+0x10/0x18


Thanks,
Peng.