Currently, in ath11k_ahb_fw_resources_init(), iommu domain
mapping is done only for the chipsets having fixed firmware
memory. Also, for such chipsets, mapping is done only if it
does not have TrustZone support.

During deinitialization, only if TrustZone support is not there,
iommu is unmapped back. However, for non fixed firmware memory
chipsets, TrustZone support is not there and this makes the
condition check to true and it tries to unmap the memory which
was not mapped during initialization.

This leads to the following trace -

[   83.198790] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
[   83.259537] Modules linked in: ath11k_ahb ath11k qmi_helpers
.. snip ..
[   83.280286] pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   83.287228] pc : __iommu_unmap+0x30/0x140
[   83.293907] lr : iommu_unmap+0x5c/0xa4
[   83.298072] sp : ffff80000b3abad0
.. snip ..
[   83.369175] Call trace:
[   83.376282]  __iommu_unmap+0x30/0x140
[   83.378541]  iommu_unmap+0x5c/0xa4
[   83.382360]  ath11k_ahb_fw_resource_deinit.part.12+0x2c/0xac [ath11k_ahb]
[   83.385666]  ath11k_ahb_free_resources+0x140/0x17c [ath11k_ahb]
[   83.392521]  ath11k_ahb_shutdown+0x34/0x40 [ath11k_ahb]
[   83.398248]  platform_shutdown+0x20/0x2c
[   83.403455]  device_shutdown+0x16c/0x1c4
[   83.407621]  kernel_restart_prepare+0x34/0x3c
[   83.411529]  kernel_restart+0x14/0x74
[   83.415781]  __do_sys_reboot+0x1c4/0x22c
[   83.419427]  __arm64_sys_reboot+0x1c/0x24
[   83.423420]  invoke_syscall+0x44/0xfc
[   83.427326]  el0_svc_common.constprop.3+0xac/0xe8
[   83.430974]  do_el0_svc+0xa0/0xa8
[   83.435659]  el0_svc+0x1c/0x44
[   83.438957]  el0t_64_sync_handler+0x60/0x144
[   83.441910]  el0t_64_sync+0x15c/0x160
[   83.446343] Code: aa0103f4 f9400001 f90027a1 d2800001 (f94006a0)
[   83.449903] ---[ end trace 0000000000000000 ]---

This can be reproduced by probing an AHB chipset which is not
having a fixed memory region. During reboot (or rmmod) trace
can be seen.

Fix this issue by adding a condition check on firmware fixed memory
hw_param as done in the counter initialization function.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.7.0.1-01744-QCAHKSWPL_SILICONZ-1

Fixes: f9eec494 ("ath11k: Add support for targets without trustzone")
Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230309095308.24937-1-quic_adisi@quicinc.com