linux-kernel - Re: [PATCH 1/2] usb: xhci-mtk: remove unnecessary assignments in periodic TT scheduler

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Date:   Wed, 31 Mar 2021 16:30:55 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Ikjoon Jang <ikjn@...omium.org>, Yaqii Wu <Yaqii.Wu@...iatek.com>
CC:     <linux-usb@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH 1/2] usb: xhci-mtk: remove unnecessary assignments in
 periodic TT scheduler

cc Yaqii Wu <Yaqii.Wu@...iatek.com>

I'll test it , thanks

On Tue, 2021-03-30 at 16:06 +0800, Ikjoon Jang wrote:
> Remove unnecessary variables in check_sch_bw().
> No functional changes, just for better readability.
> 
> Signed-off-by: Ikjoon Jang <ikjn@...omium.org>
> ---
> 
>  drivers/usb/host/xhci-mtk-sch.c | 52 +++++++++++++--------------------
>  1 file changed, 21 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-mtk-sch.c b/drivers/usb/host/xhci-mtk-sch.c
> index a59d1f6d4744..0cb41007ec65 100644
> --- a/drivers/usb/host/xhci-mtk-sch.c
> +++ b/drivers/usb/host/xhci-mtk-sch.c
> @@ -479,6 +479,9 @@ static int check_sch_tt(struct mu3h_sch_ep_info *sch_ep, u32 offset)
>  	u32 start_cs, last_cs;
>  	int i;
>  
> +	if (!sch_ep->sch_tt)
> +		return 0;
> +
>  	start_ss = offset % 8;
>  
>  	if (sch_ep->ep_type == ISOC_OUT_EP) {
> @@ -606,54 +609,41 @@ static u32 get_esit_boundary(struct mu3h_sch_ep_info *sch_ep)
>  static int check_sch_bw(struct mu3h_sch_bw_info *sch_bw,
>  			struct mu3h_sch_ep_info *sch_ep)
>  {
> -	u32 offset;
> -	u32 min_bw;
> -	u32 min_index;
> -	u32 worst_bw;
> -	u32 bw_boundary;
> -	u32 esit_boundary;
> -	u32 min_num_budget;
> -	u32 min_cs_count;
> -	int ret = 0;
> +	int i, found = -1;
> +	const u32 esit_boundary = get_esit_boundary(sch_ep);
> +	const u32 bw_boundary = get_bw_boundary(sch_ep->speed);
> +	u32 min_bw = ~0;
>  
>  	/*
>  	 * Search through all possible schedule microframes.
>  	 * and find a microframe where its worst bandwidth is minimum.
>  	 */
> -	min_bw = ~0;
> -	min_index = 0;
> -	min_cs_count = sch_ep->cs_count;
> -	min_num_budget = sch_ep->num_budget_microframes;
> -	esit_boundary = get_esit_boundary(sch_ep);
> -	for (offset = 0; offset < sch_ep->esit; offset++) {
> -		if (sch_ep->sch_tt) {
> -			ret = check_sch_tt(sch_ep, offset);
> -			if (ret)
> -				continue;
> -		}
> +	for (i = 0; i < sch_ep->esit; i++) {
> +		u32 worst_bw;
>  
> -		if ((offset + sch_ep->num_budget_microframes) > esit_boundary)
> +		if ((i + sch_ep->num_budget_microframes) > esit_boundary)
>  			break;
>  
> -		worst_bw = get_max_bw(sch_bw, sch_ep, offset);
> +		if (check_sch_tt(sch_ep, i))
> +			continue;
> +
> +		worst_bw = get_max_bw(sch_bw, sch_ep, i);
> +		if (worst_bw > bw_boundary)
> +			continue;
> +
>  		if (min_bw > worst_bw) {
>  			min_bw = worst_bw;
> -			min_index = offset;
> -			min_cs_count = sch_ep->cs_count;
> -			min_num_budget = sch_ep->num_budget_microframes;
> +			found = i;
>  		}
>  		if (min_bw == 0)
>  			break;
>  	}
>  
> -	bw_boundary = get_bw_boundary(sch_ep->speed);
>  	/* check bandwidth */
> -	if (min_bw > bw_boundary)
> -		return ret ? ret : -ESCH_BW_OVERFLOW;
> +	if (found < 0)
> +		return -ESCH_BW_OVERFLOW;
>  
> -	sch_ep->offset = min_index;
> -	sch_ep->cs_count = min_cs_count;
> -	sch_ep->num_budget_microframes = min_num_budget;
> +	sch_ep->offset = found;
>  
>  	return load_ep_bw(sch_bw, sch_ep, true);
>  }