lkml.org 
[lkml]   [2014]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] usb: xhci: Prefer endpoint context dequeue pointer over stopped_trb
Hi,

On 04/15/2014 09:42 PM, Julius Werner wrote:
> +hdegoede
>
>> I tried to apply this patch on top of 3.15-rc1, but it fails because of the
>> streams support added to xhci_find_new_dequeue_state()
>>
>> After some manual editing the interesting parts of
>> xhci_find_new_dequeue_state() looks like this:
>>
>> @@ -577,46 +568,57 @@ void xhci_find_new_dequeue_state(struct xhci_hcd
>> *xhci,
>> if (ep->ep_state & EP_HAS_STREAMS) {
>> struct xhci_stream_ctx *ctx =
>> &ep->stream_info->stream_ctx_array[stream_id];
>> - state->new_cycle_state = 0x1 &
>> le64_to_cpu(ctx->stream_ring);
>> + hw_dequeue = le64_to_cpu(ctx->stream_ring);
>> } else {
>> struct xhci_ep_ctx *ep_ctx
>>
>> = xhci_get_ep_ctx(xhci, dev->out_ctx, ep_index);
>> - state->new_cycle_state = 0x1 & le64_to_cpu(ep_ctx->deq);
>> + hw_dequeue = le64_to_cpu(ep_ctx->deq);
>> }
>>
>> + /* Find virtual address and segment of hardware dequeue pointer */
>>
>> + state->new_deq_seg = ep_ring->deq_seg;
>> + state->new_deq_ptr = ep_ring->dequeue;
>> + while (xhci_trb_virt_to_dma(state->new_deq_seg, state->new_deq_ptr)
>> + != (dma_addr_t)(hw_dequeue & ~0x1)) {
>> + next_trb(xhci, ep_ring, &state->new_deq_seg,
>> + &state->new_deq_ptr);
>> + if (state->new_deq_ptr == ep_ring->dequeue) {
>> + WARN_ON(1);
>> + return;
>> + }
>> + }
>>
>> Also the comparison of the dequeue pointers, using (hw_dequeue & ~0x1) might
>> have some troubles with streams. Endpoint context TR dequeue pointer LO
>> field has bits 3:1 reserved (probably zero) but stream context uses those
>> bits. Would it make sense to use (hw_dequeue & ~0xf) here instead?
>
> Ah, yes, looks like that patch wasn't in Linus' tree yet back when I
> wrote this. I think your merge looks pretty good... just use
> (hw_dequeue & ~0xf) instead of (hw_dequeue & ~0x1) to get the pointer
> as you said, and this should work fine.
>
>> But I'm still concerned about the dequeue pointer in the streams case.
>> streams may be nested, we might be pointing at another stream context
>> instead of the dequeue pointer.

Since I've not followed the entire discussion previously to this I cannot
really provide any useful feedback on this patch. Other then 2 remarks:

1) We don't use nested streams, so no need to worry about those
2) You're right that for streams to get the dequeue address you need
to mask with ~0xf

Regards,

Hans


\
 
 \ /
  Last update: 2014-04-15 23:01    [W:0.039 / U:92.580 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site