[PATCH v2][for 4.14] xhci: allow TRACE to work with EVENT ring dequeue

[Adam Wallis]

On 9/25/2017 5:59 AM, Mathias Nyman wrote:
> On 22.09.2017 22:55, Adam Wallis wrote:
>> inc_deq() currently bails earlier for EVENT rings than the common return
>> point of the function, due to the fact that EVENT rings do not have
>> link TRBs. The unfortunate side effect of this is that the very useful
>> trace_xhci_inc_deq() function is not called/usable for EVENT ring
>> debug.
> 
> True, makes sense to trace the event ring deq ptr as well.
> 
>>
>> This patch provides a refactor by removing the multiple return exit
>> points into a single return which additionally allows for all rings to
>> use the trace function.
>>
>> Signed-off-by: Adam Wallis <awallis at codeaurora.org>
>> ---
>> Changes in v2: undo accidental line removal at end of patch
>>
>>   drivers/usb/host/xhci-ring.c | 32 ++++++++++++++++----------------
>>   1 file changed, 16 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
>> index a944365..3960ba9 100644
>> --- a/drivers/usb/host/xhci-ring.c
>> +++ b/drivers/usb/host/xhci-ring.c
>> @@ -171,23 +171,23 @@ static void inc_deq(struct xhci_hcd *xhci, struct
>> xhci_ring *ring)
>>       if (ring->type == TYPE_EVENT) {
>>           if (!last_trb_on_seg(ring->deq_seg, ring->dequeue)) {
>>               ring->dequeue++;
>> -            return;
>> +        } else {
>> +            if (last_trb_on_ring(ring, ring->deq_seg,
>> +                ring->dequeue))
>> +                ring->cycle_state ^= 1;
>> +            ring->deq_seg = ring->deq_seg->next;
>> +            ring->dequeue = ring->deq_seg->trbs;
>> +        }
>> +    } else {
>> +        /* All other rings have link trbs */
>> +        if (!trb_is_link(ring->dequeue)) {
>> +            ring->dequeue++;
>> +            ring->num_trbs_free++;
>> +        }
>> +        while (trb_is_link(ring->dequeue)) {
>> +            ring->deq_seg = ring->deq_seg->next;
>> +            ring->dequeue = ring->deq_seg->trbs;
> 
> The added level of indentation makes it a little bit messier.
> How about just using goto out; instead of return?
> 
> out:
>     trace_xhci_inc_deq(ring);

My first version of this patch (before submission) actually had gotos, but I
wasn't sure if you would accept. I agree that this will be much cleaner. v3
patch en route!

> 
> -Mathias
> 
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-- 
Adam Wallis
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.