Re: [PATCH 0/7] slimbus: qcom-ngd-ctrl: Fix some race conditions and deadlocks

[Dmitry Baryshkov]

On Mon, Mar 09, 2026 at 11:09:01PM -0500, Bjorn Andersson wrote:
> When the qcom-ngd-ctrl driver is probed after the ADSP remoteproc, the
> SSR notifier will fire immediately, which results in
> qcom_slim_ngd_ssr_pdr_notify() attempting to schedule_work() on an
> unitialized work_struct.
> 
> The concrete result of this is that my db845c/RB3 now fails to boot 100%
> of the time.
> 
> In reviewing the problematic code, a few other problems where
> discovered, such that platform_driver_unregister() is used to unregister
> the child device.
> 
> Lastly, with the db845c booting, it was determined that attempting to
> stop the ADSP remoteproc causes the slimbus driver to deadlock.
> 
> Note that while this solves the problems described above, and unblock
> boot as well as restart of the remoteproc, this stack needs more love.
> 
> Upon tearing down the slimbus controller (when the ADSP goes down), the
> slimbus devices attempts to access their slimbus devices - which is
> prevented by the controller being runtime suspended. This results in a
> wall of errors in the log, about failing transactions.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx>
> ---
> Bjorn Andersson (7):
>       slimbus: qcom-ngd-ctrl: Fix up platform_driver registration
>       slimbus: qcom-ngd-ctrl: Fix probe error path ordering
>       slimbus: qcom-ngd-ctrl: Correct PDR and SSR cleanup ownership
>       slimbus: qcom-ngd-ctrl: Register callbacks after creating the ngd
>       slimbus: qcom-ngd-ctrl: Initialize controller resources in controller
>       slimbus: qcom-ngd-ctrl: Balance pm_runtime enablement for NGD
>       slimbus: qcom-ngd-ctrl: Avoid ABBA on tx_lock/ctrl->lock
> 
>  drivers/slimbus/qcom-ngd-ctrl.c | 127 +++++++++++++++++++++++++---------------
>  1 file changed, 80 insertions(+), 47 deletions(-)
> ---
> base-commit: a0ae2a256046c0c5d3778d1a194ff2e171f16e5f
> change-id: 20260211-slim-ngd-dev-74166f29f035
> 
> Best regards,
> -- 
> Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx>

Bjorn,

While you are at it, it looks like there is another possible issue:
ngd->base is set after platform_device_add(), possibly letting NGD
driver to use uninitialized base.

-- 
With best wishes
Dmitry