diff mbox series

xhci: No XHCI_TRUST_TX_LENGTH check in the absence of matching TD

Message ID 20191113130609.32831-1-eli.billauer@gmail.com (mailing list archive)
State New, archived
Headers show
Series xhci: No XHCI_TRUST_TX_LENGTH check in the absence of matching TD | expand

Commit Message

Eli Billauer Nov. 13, 2019, 1:06 p.m. UTC 
From: Eli Billauer <eli.billauer@gmail.com>

When an IN transfer ends with a short packet, the xHCI controller is
required to submit an event TRB with Completion Code COMP_SHORT_PACKET
against the data TRB that was in effect when the short packet arrived, as
well as any event TRBs it submits on behalf of this transfer.

Alas, some controllers (e.g. Renesas) mark the subsequent events TRBs (if
any) with COMP_SUCCESS. As these subsequent event TRBs are useless, they
are ignored on the basis that they have no matching TD queued (it was
dequeued in response to the first COMP_SHORT_PACKET event TRB).

Accordingly, the quirk handling and kernel log warning is moved to after
the TD match check, in particular in order to avoid unnecessary warnings
messages.

Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
---
 drivers/usb/host/xhci-ring.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

Comments

Mathias Nyman Nov. 18, 2019, 4:08 p.m. UTC | #1 
On 13.11.2019 15.06, eli.billauer@gmail.com wrote:
> From: Eli Billauer <eli.billauer@gmail.com>
> 
> When an IN transfer ends with a short packet, the xHCI controller is
> required to submit an event TRB with Completion Code COMP_SHORT_PACKET
> against the data TRB that was in effect when the short packet arrived, as
> well as any event TRBs it submits on behalf of this transfer.
> 
> Alas, some controllers (e.g. Renesas) mark the subsequent events TRBs (if
> any) with COMP_SUCCESS. As these subsequent event TRBs are useless, they
> are ignored on the basis that they have no matching TD queued (it was
> dequeued in response to the first COMP_SHORT_PACKET event TRB).
> 
> Accordingly, the quirk handling and kernel log warning is moved to after
> the TD match check, in particular in order to avoid unnecessary warnings
> messages.
> 
> Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
> ---
>   drivers/usb/host/xhci-ring.c | 19 +++++++++++--------
>   1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 9741cdeea9d7..96680eb71a45 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -2376,14 +2376,6 @@ static int handle_tx_event(struct xhci_hcd *xhci,
>   	 * transfer type
>   	 */
>   	case COMP_SUCCESS:
> -		if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
> -			break;
> -		if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
> -			trb_comp_code = COMP_SHORT_PACKET;
> -		else
> -			xhci_warn_ratelimited(xhci,
> -					      "WARN Successful completion on short TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
> -					      slot_id, ep_index);
>   	case COMP_SHORT_PACKET:
>   		break;
>   	/* Completion codes for endpoint stopped state */
> @@ -2586,6 +2578,17 @@ static int handle_tx_event(struct xhci_hcd *xhci,
>   			skip_isoc_td(xhci, td, event, ep, &status);
>   			goto cleanup;
>   		}
> +
> +		if ((trb_comp_code == COMP_SUCCESS) &&
> +		    (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) != 0)) {
> +			if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
> +				trb_comp_code = COMP_SHORT_PACKET;
> +			else
> +				xhci_warn_ratelimited(xhci,
> +						      "WARN Successful completion on short TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
> +						      slot_id, ep_index);
> +		}
> +
>   		if (trb_comp_code == COMP_SHORT_PACKET)
>   			ep_ring->last_td_was_short = true;
>   		else
> 

I'd hate to rip out the success case from the switch statement where the other
completion codes are handled. We're still only making a choice about a warning
message

How about handling all COMP_SUCCESS cases with remaining data after a short
transfer as COMP_SHORT_PACKET by default?

The code below won't behave exactly the same as in your patch, but should
do the trick in your Renesas case as well. Can you try it out?

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9ebaa8e132a9..d23f7408c81f 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2381,7 +2381,8 @@ static int handle_tx_event(struct xhci_hcd *xhci,
         case COMP_SUCCESS:
                 if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
                         break;
-               if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
+               if (xhci->quirks & XHCI_TRUST_TX_LENGTH ||
+                   ep_ring->last_td_was_short)
                         trb_comp_code = COMP_SHORT_PACKET;
                 else
                         xhci_warn_ratelimited(xhci,
Eli Billauer Nov. 19, 2019, 11:48 a.m. UTC | #2 
Hello,

I've taken the liberty to add parentheses for sake of clarity, so I 
tested the following patch (against kernel 5.3.0) with my Resesas USB 
controller. And as expected, it does the job: The warnings are not printed.

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9741cdeea9d7..b062e3a19e95 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2378,7 +2378,8 @@ static int handle_tx_event(struct xhci_hcd *xhci,
      case COMP_SUCCESS:
          if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
              break;
-        if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
+        if ((xhci->quirks & XHCI_TRUST_TX_LENGTH) ||
+            ep_ring->last_td_was_short)
              trb_comp_code = COMP_SHORT_PACKET;
          else
              xhci_warn_ratelimited(xhci,

So it solves the problem for me, and hopefully for future Renesas 
controllers with the same issue.

Regards,
    Eli

On 18/11/19 18:08, Mathias Nyman wrote:
> On 13.11.2019 15.06, eli.billauer@gmail.com wrote:
>> From: Eli Billauer <eli.billauer@gmail.com>
>>
>> When an IN transfer ends with a short packet, the xHCI controller is
>> required to submit an event TRB with Completion Code COMP_SHORT_PACKET
>> against the data TRB that was in effect when the short packet 
>> arrived, as
>> well as any event TRBs it submits on behalf of this transfer.
>>
>> Alas, some controllers (e.g. Renesas) mark the subsequent events TRBs 
>> (if
>> any) with COMP_SUCCESS. As these subsequent event TRBs are useless, they
>> are ignored on the basis that they have no matching TD queued (it was
>> dequeued in response to the first COMP_SHORT_PACKET event TRB).
>>
>> Accordingly, the quirk handling and kernel log warning is moved to after
>> the TD match check, in particular in order to avoid unnecessary warnings
>> messages.
>>
>> Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
>> ---
>>   drivers/usb/host/xhci-ring.c | 19 +++++++++++--------
>>   1 file changed, 11 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
>> index 9741cdeea9d7..96680eb71a45 100644
>> --- a/drivers/usb/host/xhci-ring.c
>> +++ b/drivers/usb/host/xhci-ring.c
>> @@ -2376,14 +2376,6 @@ static int handle_tx_event(struct xhci_hcd *xhci,
>>        * transfer type
>>        */
>>       case COMP_SUCCESS:
>> -        if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
>> -            break;
>> -        if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
>> -            trb_comp_code = COMP_SHORT_PACKET;
>> -        else
>> -            xhci_warn_ratelimited(xhci,
>> -                          "WARN Successful completion on short TX 
>> for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
>> -                          slot_id, ep_index);
>>       case COMP_SHORT_PACKET:
>>           break;
>>       /* Completion codes for endpoint stopped state */
>> @@ -2586,6 +2578,17 @@ static int handle_tx_event(struct xhci_hcd *xhci,
>>               skip_isoc_td(xhci, td, event, ep, &status);
>>               goto cleanup;
>>           }
>> +
>> +        if ((trb_comp_code == COMP_SUCCESS) &&
>> +            (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) != 0)) {
>> +            if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
>> +                trb_comp_code = COMP_SHORT_PACKET;
>> +            else
>> +                xhci_warn_ratelimited(xhci,
>> +                              "WARN Successful completion on short 
>> TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
>> +                              slot_id, ep_index);
>> +        }
>> +
>>           if (trb_comp_code == COMP_SHORT_PACKET)
>>               ep_ring->last_td_was_short = true;
>>           else
>>
>
> I'd hate to rip out the success case from the switch statement where 
> the other
> completion codes are handled. We're still only making a choice about a 
> warning
> message
>
> How about handling all COMP_SUCCESS cases with remaining data after a 
> short
> transfer as COMP_SHORT_PACKET by default?
>
> The code below won't behave exactly the same as in your patch, but should
> do the trick in your Renesas case as well. Can you try it out?
>
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 9ebaa8e132a9..d23f7408c81f 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -2381,7 +2381,8 @@ static int handle_tx_event(struct xhci_hcd *xhci,
>         case COMP_SUCCESS:
>                 if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
>                         break;
> -               if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
> +               if (xhci->quirks & XHCI_TRUST_TX_LENGTH ||
> +                   ep_ring->last_td_was_short)
>                         trb_comp_code = COMP_SHORT_PACKET;
>                 else
>                         xhci_warn_ratelimited(xhci,
>
>
diff mbox series

Patch

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9741cdeea9d7..96680eb71a45 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2376,14 +2376,6 @@  static int handle_tx_event(struct xhci_hcd *xhci,
 	 * transfer type
 	 */
 	case COMP_SUCCESS:
-		if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
-			break;
-		if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
-			trb_comp_code = COMP_SHORT_PACKET;
-		else
-			xhci_warn_ratelimited(xhci,
-					      "WARN Successful completion on short TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
-					      slot_id, ep_index);
 	case COMP_SHORT_PACKET:
 		break;
 	/* Completion codes for endpoint stopped state */
@@ -2586,6 +2578,17 @@  static int handle_tx_event(struct xhci_hcd *xhci,
 			skip_isoc_td(xhci, td, event, ep, &status);
 			goto cleanup;
 		}
+
+		if ((trb_comp_code == COMP_SUCCESS) &&
+		    (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) != 0)) {
+			if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
+				trb_comp_code = COMP_SHORT_PACKET;
+			else
+				xhci_warn_ratelimited(xhci,
+						      "WARN Successful completion on short TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
+						      slot_id, ep_index);
+		}
+
 		if (trb_comp_code == COMP_SHORT_PACKET)
 			ep_ring->last_td_was_short = true;
 		else