[PATCH 2/3] staging: dwc2: add NAK holdoff patch from downstream Pi kernel

Matthijs Kooijman matthijs at stdin.nl
Mon Aug 12 07:35:50 UTC 2013


Hi Paul,

> Add the NAK holdoff patch from the downstream Raspberry Pi kernel.
> This allows the transfer scheduler to better handle "cheeky devices
> that just hold off using NAKs".

> @@ -365,6 +366,7 @@ struct dwc2_hsotg {
>  	u8 otg_port;
>  	u32 *frame_list;
>  	dma_addr_t frame_list_dma;
> +	int next_sched_frame;

This variable is still not really used, I think. Most of the mentions in
the patch are assignments, except for these two:

> +		if (list_empty(&hsotg->periodic_sched_inactive) ||
> +		    dwc2_frame_num_le(qh->sched_frame, hsotg->next_sched_frame))
> +			hsotg->next_sched_frame = qh->sched_frame;
> +
...
> +				if (!dwc2_frame_num_le(hsotg->next_sched_frame,
> +						       qh->sched_frame))
> +					hsotg->next_sched_frame =
> +							qh->sched_frame;

However, these two "uses" of the variable have only the single purpose
of updating the variable itself, no other behaviour is influenced by it.
In effect, the variable does not influence the code at all and can be
dropped, significantly simplifying this patch.

Gr.

Matthijs


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