[PATCH] wifi: ath11k: run ahb shutdown() teardown only on WCN6750

The AHB shutdown() callback was introduced solely for WCN6750, which has
to stop DMA before the SMMU is torn down at system reboot/shutdown. It
was registered unconditionally in the shared ath11k_ahb_driver, so it also
runs on the IPQ AHB targets (IPQ8074/IPQ6018/IPQ5018), which never had a
shutdown() handler before and have no such SMMU requirement.

On IPQ6018 the shutdown teardown stops the WCSS Q6 remote processor
firmware. Stopping the Q6 firmware leaves shared WCSS state such that the
boot ROM (SBL1) hangs during DDR training on the following warm reset;
only a cold (power-on) reset recovers. A plain reboot therefore never
comes back and needs a physical power cycle.

This was pinned by bisecting the teardown at reboot: skipping
ath11k_qmi_firmware_stop() (i.e. not stopping the Q6) is what lets the
warm reset train DDR and boot normally, whereas none of the q6v5 power,
reset or clock steps reproduce it on their own.

Restrict the shutdown() teardown to WCN6750, restoring the pre-regression
behaviour for the IPQ AHB targets. On reboot/shutdown the whole SoC is
reset by the boot chain, which re-initializes the WCSS from scratch, so no
teardown is needed there. Module removal (rmmod / remove()) is unchanged.

Verified on a MikroTik Chateau 5G R17 ax (IPQ6018): before, a plain reboot
froze in SBL1 at "sbl1_ddr_set_params"; after, SBL1 reaches "SBL1, End",
trains DDR and boots the kernel across repeated reboots.

Fixes: ac41c2b642b1 ("wifi: ath11k: Register shutdown handler for WCN6750")
Cc: [email protected]
Cc: Manikanta Pubbisetty <[email protected]>
Signed-off-by: André Valentin <[email protected]>
---
 drivers/net/wireless/ath/ath11k/ahb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/wireless/ath/ath11k/ahb.c b/drivers/net/wireless/ath/ath11k/ahb.c
index 1e1dea4..749d8bf 100644
--- a/drivers/net/wireless/ath/ath11k/ahb.c
+++ b/drivers/net/wireless/ath/ath11k/ahb.c
@@ -1288,6 +1288,18 @@ static void ath11k_ahb_shutdown(struct platform_device *pdev)
 	 * remove() is invoked during rmmod & shutdown() during
 	 * system reboot/shutdown.
 	 */
+
+	/* The shutdown() callback was added for WCN6750, which has to stop DMA
+	 * before the SMMU is torn down. The other AHB targets (IPQ8074/IPQ6018/
+	 * IPQ5018) have no such requirement, and running the teardown here stops
+	 * the WCSS Q6 firmware, which leaves shared state that hangs the boot ROM
+	 * (SBL1) during DDR training on the following warm reset -- only a cold
+	 * (power-on) reset recovers. Skip it on those targets; the SoC reset
+	 * re-initializes the WCSS from scratch.
+	 */
+	if (ab->hw_rev != ATH11K_HW_WCN6750_HW10)
+		return;
+
 	ath11k_ahb_remove_prepare(ab);
 
 	if (!(test_bit(ATH11K_FLAG_REGISTERED, &ab->dev_flags)))

base-commit: f9a2394a23482bfd330911e9c8295b71724feacd
-- 
2.47.3