[PATCH v3] phy: qcom-qusb2: Fix NULL pointer dereference on early suspend

[Abel Vesa]

On 25-12-11 16:35:36, Loic Poulain wrote:
> Enabling runtime PM before attaching the QPHY instance as driver data
> can lead to a NULL pointer dereference in runtime PM callbacks that
> expect valid driver data. There is a small window where the suspend
> callback may run after PM runtime enabling and before runtime forbid.
> This causes a sporadic crash during boot:
> 
> ```
> Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a1
> [...]
> CPU: 0 UID: 0 PID: 11 Comm: kworker/0:1 Not tainted 6.16.7+ #116 PREEMPT
> Workqueue: pm pm_runtime_work
> pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : qusb2_phy_runtime_suspend+0x14/0x1e0 [phy_qcom_qusb2]
> lr : pm_generic_runtime_suspend+0x2c/0x44
> [...]
> ```
> 
> Attach the QPHY instance as driver data before enabling runtime PM to
> prevent NULL pointer dereference in runtime PM callbacks.
> 
> Reorder pm_runtime_enable() and pm_runtime_forbid() to prevent a
> short window where an unnecessary runtime suspend can occur.
> 
> Use the devres-managed version to ensure PM runtime is symmetrically
> disabled during driver removal for proper cleanup.
> 
> Fixes: 891a96f65ac3 ("phy: qcom-qusb2: Add support for runtime PM")
> Signed-off-by: Loic Poulain <loic.poulain at oss.qualcomm.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>

Reviewed-by: Abel Vesa <abel.vesa at oss.qualcomm.com>