Re: [PATCH 23/24] usb: xhci: add warning message specifying which Set TR Deq failed

["Michał Pecio" <michal.pecio@gmail.com>]

On Thu, 15 May 2025 16:56:20 +0300, Mathias Nyman wrote:
> From: Niklas Neronin <niklas.neronin@linux.intel.com>
> 
> Currently, errors from the Set TR Deq command are not handled.
> Add a warning message to specify the slot, endpoint, and TRB address
> when a Set TR Deq command fails. This additional information will aid
> in debugging such failures.
> 
> Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
> ---
>  drivers/usb/host/xhci-ring.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci-ring.c
> b/drivers/usb/host/xhci-ring.c index e3c823e1caee..eff6b84dc915 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -1448,6 +1448,11 @@ static void xhci_handle_cmd_set_deq(struct
> xhci_hcd *xhci, int slot_id, unsigned int ep_state;
>  		unsigned int slot_state;
>  
> +		xhci_warn(xhci, "Set TR Deq error for TRB 0x%llx in slot %d ep %u\n",
> +			  (unsigned long long)xhci_trb_virt_to_dma(ep->queued_deq_seg,
> +						ep->queued_deq_ptr),

Is printing this pointer actually useful? It doesn't tell why
the error happened. It will not relate to other messages - the
command failed, so dequeue stays at its old position.

> +			  slot_id, ep_index);
> +
>  		switch (cmd_comp_code) {
>  		case COMP_TRB_ERROR:
>  			xhci_warn(xhci, "WARN Set TR Deq Ptr cmd invalid because of stream ID configuration\n");

This will now become a multi-line log message, even though actual
information it contains could fit in one line.

How about replacing this new line and the whole switch with:

+               ep_state = GET_EP_CTX_STATE(ep_ctx);
+               slot_state = GET_SLOT_STATE(le32_to_cpu(slot_ctx->dev_state));
+
+               xhci_warn(xhci, "Set TR Dequeue %s for slot %d ep %d (%s/%s)\n",
+                               xhci_trb_comp_code_string(cmd_comp_code), slot_id, ep_index,
+                               xhci_slot_state_string(slot_state), xhci_ep_state_string(ep_state));

Example output:
xhci_hcd 0000:02:00.0: Set TR Dequeue TRB Error for slot 1 ep 6 (configured/stopped)

IMO this has the further benefit that "TRB Error" is something I can
search in the spec, while "because of stream ID configuration" is not.
And it isn't even the true treason in every case of TRB Error.

Thanks,
Michal