Re: [PATCH RESEND RFC 3/3] net: ath11k: add lockup simulation via debugfs

[Jeff Johnson <jeff.johnson@oss.qualcomm.com>]

On 3/30/2026 3:05 AM, Matthew Leach wrote:
> Add a debugfs command to simulate a firmware lockup.
> 
> This does not hang the hardware. Instead, it forces the driver down an
> error path that reproduces the sequence observed during real lockups:
> 
>   ath11k_pci 0000:03:00.0: failed to transmit frame -12
>   ath11k_pci 0000:03:00.0: failed to transmit frame -12
>   ath11k_pci 0000:03:00.0: failed to transmit frame -12
>   ...
>   ath11k_pci 0000:03:00.0: wmi command 28680 timeout
>   ath11k_pci 0000:03:00.0: failed to submit WMI_MGMT_TX_SEND_CMDID cmd
>   ath11k_pci 0000:03:00.0: failed to send mgmt frame: -11
> 
> This allows validation of the firmware lockup detection and recovery
> mechanism without requiring a real hardware failure.
> 
> Signed-off-by: Matthew Leach <matthew.leach@collabora.com>
> ---
>  drivers/net/wireless/ath/ath11k/core.h    | 1 +
>  drivers/net/wireless/ath/ath11k/debugfs.c | 7 ++++++-
>  drivers/net/wireless/ath/ath11k/hal.c     | 7 +++++--
>  drivers/net/wireless/ath/ath11k/htc.c     | 2 +-
>  drivers/net/wireless/ath/ath11k/wmi.c     | 6 +++++-
>  5 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/core.h b/drivers/net/wireless/ath/ath11k/core.h
> index 221dcd23b3dd..44b02ae1e85b 100644
> --- a/drivers/net/wireless/ath/ath11k/core.h
> +++ b/drivers/net/wireless/ath/ath11k/core.h
> @@ -1041,6 +1041,7 @@ struct ath11k_base {
>  	struct ath11k_dbring_cap *db_caps;
>  	u32 num_db_cap;
>  	u64 last_frame_tx_error_jiffies;
> +	bool simulate_lockup;
>  
>  	/* To synchronize 11d scan vdev id */
>  	struct mutex vdev_id_11d_lock;
> diff --git a/drivers/net/wireless/ath/ath11k/debugfs.c b/drivers/net/wireless/ath/ath11k/debugfs.c
> index 0c1138407838..ca0b72a3e0b0 100644
> --- a/drivers/net/wireless/ath/ath11k/debugfs.c
> +++ b/drivers/net/wireless/ath/ath11k/debugfs.c
> @@ -356,7 +356,8 @@ static ssize_t ath11k_read_simulate_fw_crash(struct file *file,
>  	const char buf[] =
>  		"To simulate firmware crash write one of the keywords to this file:\n"
>  		"`assert` - this will send WMI_FORCE_FW_HANG_CMDID to firmware to cause assert.\n"
> -		"`hw-restart` - this will simply queue hw restart without fw/hw actually crashing.\n";
> +		"`hw-restart` - this will simply queue hw restart without fw/hw actually crashing.\n"
> +		"`lockup` - simulate a firmware lockup without the h/w actually hanging.\n";
>  
>  	return simple_read_from_buffer(user_buf, count, ppos, buf, strlen(buf));
>  }
> @@ -413,6 +414,10 @@ static ssize_t ath11k_write_simulate_fw_crash(struct file *file,
>  		ath11k_info(ab, "user requested hw restart\n");
>  		queue_work(ab->workqueue_aux, &ab->reset_work);
>  		ret = 0;
> +	} else if (!strcmp(buf, "lockup")) {
> +		ath11k_info(ab, "simulating lockup\n");
> +		ab->simulate_lockup = true;
> +		ret = 0;
>  	} else {
>  		ret = -EINVAL;
>  		goto exit;
> diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
> index e821e5a62c1c..e01fb17a4734 100644
> --- a/drivers/net/wireless/ath/ath11k/hal.c
> +++ b/drivers/net/wireless/ath/ath11k/hal.c
> @@ -691,7 +691,7 @@ int ath11k_hal_srng_dst_num_free(struct ath11k_base *ab, struct hal_srng *srng,
>  
>  	tp = srng->u.dst_ring.tp;
>  
> -	if (sync_hw_ptr) {
> +	if (sync_hw_ptr && !ab->simulate_lockup) {
>  		hp = *srng->u.dst_ring.hp_addr;
>  		srng->u.dst_ring.cached_hp = hp;
>  	} else {
> @@ -743,7 +743,7 @@ u32 *ath11k_hal_srng_src_get_next_entry(struct ath11k_base *ab,
>  	 */
>  	next_hp = (srng->u.src_ring.hp + srng->entry_size) % srng->ring_size;
>  
> -	if (next_hp == srng->u.src_ring.cached_tp)
> +	if (next_hp == srng->u.src_ring.cached_tp || ab->simulate_lockup)
>  		return NULL;
>  
>  	desc = srng->ring_base_vaddr + srng->u.src_ring.hp;
> @@ -828,6 +828,9 @@ void ath11k_hal_srng_access_begin(struct ath11k_base *ab, struct hal_srng *srng)
>  
>  	lockdep_assert_held(&srng->lock);
>  
> +	if (ab->simulate_lockup)
> +		return;
> +
>  	if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
>  		srng->u.src_ring.cached_tp =
>  			*(volatile u32 *)srng->u.src_ring.tp_addr;
> diff --git a/drivers/net/wireless/ath/ath11k/htc.c b/drivers/net/wireless/ath/ath11k/htc.c
> index 4571d01cc33d..b05d04a1f5e8 100644
> --- a/drivers/net/wireless/ath/ath11k/htc.c
> +++ b/drivers/net/wireless/ath/ath11k/htc.c
> @@ -208,7 +208,7 @@ static int ath11k_htc_process_trailer(struct ath11k_htc *htc,
>  			break;
>  		}
>  
> -		if (ab->hw_params.credit_flow) {
> +		if (ab->hw_params.credit_flow && !ab->simulate_lockup) {
>  			switch (record->hdr.id) {
>  			case ATH11K_HTC_RECORD_CREDITS:
>  				len = sizeof(struct ath11k_htc_credit_report);
> diff --git a/drivers/net/wireless/ath/ath11k/wmi.c b/drivers/net/wireless/ath/ath11k/wmi.c
> index 7d9f0bcbb3b0..27d6d4a2f803 100644
> --- a/drivers/net/wireless/ath/ath11k/wmi.c
> +++ b/drivers/net/wireless/ath/ath11k/wmi.c
> @@ -345,9 +345,13 @@ int ath11k_wmi_cmd_send(struct ath11k_pdev_wmi *wmi, struct sk_buff *skb,
>  
>  		if (time_in_range64(ab->last_frame_tx_error_jiffies,
>  				    range_start, jiffies_64) &&
> -		    queue_work(ab->workqueue_aux, &ab->reset_work))
> +		    queue_work(ab->workqueue_aux, &ab->reset_work)) {
>  			ath11k_err(wmi_ab->ab,
>  				   "Firmware lockup detected.  Resetting.");
> +
> +			/* Assume that reset gets us out of lockup. */
> +			ab->simulate_lockup = false;
> +		}
>  	}
>  
>  	if (ret == -ENOBUFS)
> 

My 1st impression of this patch is that the datapath folks are not going to
like the ab->simulate_lockup checks in the hot path. But I'll let the
engineers speak for themselves.

/jeff