Re: [PATCH RFC] soc: qcom: pmic_glink: Fix device access from worker during suspend

[Johan Hovold <johan@kernel.org>]

On Fri, Jan 10, 2025 at 05:29:51PM +0200, Abel Vesa wrote:
> The pmic_glink_altmode_worker() currently gets scheduled on the system_wq.
> When the system is suspended (s2idle), the fact that the worker can be
> scheduled to run while devices are still suspended provesto be a problem
> when a Type-C retimer, switch or mux that is controlled over a bus like
> I2C, because the I2C controller is suspended.
> 
> This has been proven to be the case on the X Elite boards where such
> retimers (ParadeTech PS8830) are used in order to handle Type-C
> orientation and altmode configuration. The following warning is thrown:
> 
> [   35.134876] i2c i2c-4: Transfer while suspended
> [   35.143865] WARNING: CPU: 0 PID: 99 at drivers/i2c/i2c-core.h:56 __i2c_transfer+0xb4/0x57c [i2c_core]
> [   35.352879] Workqueue: events pmic_glink_altmode_worker [pmic_glink_altmode]
> [   35.360179] pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> [   35.455242] Call trace:
> [   35.457826]  __i2c_transfer+0xb4/0x57c [i2c_core] (P)
> [   35.463086]  i2c_transfer+0x98/0xf0 [i2c_core]
> [   35.467713]  i2c_transfer_buffer_flags+0x54/0x88 [i2c_core]
> [   35.473502]  regmap_i2c_write+0x20/0x48 [regmap_i2c]
> [   35.478659]  _regmap_raw_write_impl+0x780/0x944
> [   35.483401]  _regmap_bus_raw_write+0x60/0x7c
> [   35.487848]  _regmap_write+0x134/0x184
> [   35.491773]  regmap_write+0x54/0x78
> [   35.495418]  ps883x_set+0x58/0xec [ps883x]
> [   35.499688]  ps883x_sw_set+0x60/0x84 [ps883x]
> [   35.504223]  typec_switch_set+0x48/0x74 [typec]
> [   35.508952]  pmic_glink_altmode_worker+0x44/0x1fc [pmic_glink_altmode]
> [   35.515712]  process_scheduled_works+0x1a0/0x2d0
> [   35.520525]  worker_thread+0x2a8/0x3c8
> [   35.524449]  kthread+0xfc/0x184
> [   35.527749]  ret_from_fork+0x10/0x20
> 
> The solution here is to schedule the altmode worker on the system_freezable_wq
> instead of the system_wq. This will result in the altmode worker not being
> scheduled to run until the devices are resumed first, which will give the
> controllers like I2C a chance to resume before the transfer is requested.
> 
> Fixes: 080b4e24852b ("soc: qcom: pmic_glink: Introduce altmode support")
> Cc: stable@vger.kernel.org    # 6.3
> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>

You forgot to include:

Reported-by: Johan Hovold <johan+linaro@kernel.org>	
Link: https://lore.kernel.org/lkml/Z1CCVjEZMQ6hJ-wK@hovoldconsulting.com/

Johan