[2/2] usb: xhci-mtk: relax periodic TT bandwidth checking

Software bandwidth checking logics used by xhci-mtk puts
a quite heavy constraints to TT periodic endpoint allocations.

This patch provides a relaxed bandwidth calculation by
- Allowing multiple periodic transactions in a same microframe
  for a device with multiple interrupt endpoints.
- Using best case budget instead of maximum number of
  complete-split when calculating byte budgets on lower speed bus

Without this patch, a typical full speed audio headset with
3 periodic endpoints (audio isoc-in/out, input int-in) cannot be
configured with xhci-mtk.

Signed-off-by: Ikjoon Jang <ikjn@chromium.org>
---

 drivers/usb/host/xhci-mtk-sch.c | 68 ++++++++++-----------------------
 drivers/usb/host/xhci-mtk.h     |  2 -
 2 files changed, 20 insertions(+), 50 deletions(-)

On Tue, 2021-03-30 at 16:06 +0800, Ikjoon Jang wrote:
> Software bandwidth checking logics used by xhci-mtk puts

> a quite heavy constraints to TT periodic endpoint allocations.

> 

> This patch provides a relaxed bandwidth calculation by

> - Allowing multiple periodic transactions in a same microframe

>   for a device with multiple interrupt endpoints.

> - Using best case budget instead of maximum number of

>   complete-split when calculating byte budgets on lower speed bus

> 

> Without this patch, a typical full speed audio headset with

> 3 periodic endpoints (audio isoc-in/out, input int-in) cannot be

> configured with xhci-mtk.

> 

> Signed-off-by: Ikjoon Jang <ikjn@chromium.org>

> ---

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

I'll test it, thanks

> 

>  drivers/usb/host/xhci-mtk-sch.c | 68 ++++++++++-----------------------

>  drivers/usb/host/xhci-mtk.h     |  2 -

>  2 files changed, 20 insertions(+), 50 deletions(-)

> 

> diff --git a/drivers/usb/host/xhci-mtk-sch.c b/drivers/usb/host/xhci-mtk-sch.c

> index 0cb41007ec65..76827e48049a 100644

> --- a/drivers/usb/host/xhci-mtk-sch.c

> +++ b/drivers/usb/host/xhci-mtk-sch.c

> @@ -388,13 +388,17 @@ static void setup_sch_info(struct xhci_ep_ctx *ep_ctx,

>  		} else { /* INT_IN_EP or ISOC_IN_EP */

>  			bwb_table[0] = 0; /* start split */

>  			bwb_table[1] = 0; /* idle */

> +

> +			sch_ep->num_budget_microframes += 2;

> +			if (sch_ep->num_budget_microframes > sch_ep->esit)

> +				sch_ep->num_budget_microframes = sch_ep->esit;

>  			/*

>  			 * due to cs_count will be updated according to cs

>  			 * position, assign all remainder budget array

>  			 * elements as @bw_cost_per_microframe, but only first

>  			 * @num_budget_microframes elements will be used later

>  			 */

> -			for (i = 2; i < TT_MICROFRAMES_MAX; i++)

> +			for (i = 2; i < sch_ep->num_budget_microframes; i++)

>  				bwb_table[i] =	sch_ep->bw_cost_per_microframe;

>  		}

>  	}

> @@ -449,20 +453,17 @@ static void update_bus_bw(struct mu3h_sch_bw_info *sch_bw,

>  static int check_fs_bus_bw(struct mu3h_sch_ep_info *sch_ep, int offset)

>  {

>  	struct mu3h_sch_tt *tt = sch_ep->sch_tt;

> -	u32 num_esit, tmp;

> -	int base;

>  	int i, j;

> +	const int nr_lower_uframes =

> +		DIV_ROUND_UP(sch_ep->maxpkt, FS_PAYLOAD_MAX);

>  

> -	num_esit = XHCI_MTK_MAX_ESIT / sch_ep->esit;

> -	for (i = 0; i < num_esit; i++) {

> -		base = offset + i * sch_ep->esit;

> -

> +	for (i = offset; i < XHCI_MTK_MAX_ESIT; i += sch_ep->esit) {

>  		/*

>  		 * Compared with hs bus, no matter what ep type,

>  		 * the hub will always delay one uframe to send data

>  		 */

> -		for (j = 0; j < sch_ep->cs_count; j++) {

> -			tmp = tt->fs_bus_bw[base + j] + sch_ep->bw_cost_per_microframe;

> +		for (j = 0; j < nr_lower_uframes; j++) {

> +			u32 tmp = tt->fs_bus_bw[i + j + 1] + sch_ep->bw_cost_per_microframe;

>  			if (tmp > FS_PAYLOAD_MAX)

>  				return -ESCH_BW_OVERFLOW;

>  		}

> @@ -473,11 +474,9 @@ static int check_fs_bus_bw(struct mu3h_sch_ep_info *sch_ep, int offset)

>  

>  static int check_sch_tt(struct mu3h_sch_ep_info *sch_ep, u32 offset)

>  {

> -	struct mu3h_sch_tt *tt = sch_ep->sch_tt;

>  	u32 extra_cs_count;

>  	u32 start_ss, last_ss;

>  	u32 start_cs, last_cs;

> -	int i;

>  

>  	if (!sch_ep->sch_tt)

>  		return 0;

> @@ -494,10 +493,6 @@ static int check_sch_tt(struct mu3h_sch_ep_info *sch_ep, u32 offset)

>  		if (!(start_ss == 7 || last_ss < 6))

>  			return -ESCH_SS_Y6;

>  

> -		for (i = 0; i < sch_ep->cs_count; i++)

> -			if (test_bit(offset + i, tt->ss_bit_map))

> -				return -ESCH_SS_OVERLAP;

> -

>  	} else {

>  		u32 cs_count = DIV_ROUND_UP(sch_ep->maxpkt, FS_PAYLOAD_MAX);

>  

> @@ -524,19 +519,7 @@ static int check_sch_tt(struct mu3h_sch_ep_info *sch_ep, u32 offset)

>  		if (cs_count > 7)

>  			cs_count = 7; /* HW limit */

>  

> -		if (test_bit(offset, tt->ss_bit_map))

> -			return -ESCH_SS_OVERLAP;

> -

>  		sch_ep->cs_count = cs_count;

> -		/* one for ss, the other for idle */

> -		sch_ep->num_budget_microframes = cs_count + 2;

> -

> -		/*

> -		 * if interval=1, maxp >752, num_budge_micoframe is larger

> -		 * than sch_ep->esit, will overstep boundary

> -		 */

> -		if (sch_ep->num_budget_microframes > sch_ep->esit)

> -			sch_ep->num_budget_microframes = sch_ep->esit;

>  	}

>  

>  	return check_fs_bus_bw(sch_ep, offset);

> @@ -545,31 +528,18 @@ static int check_sch_tt(struct mu3h_sch_ep_info *sch_ep, u32 offset)

>  static void update_sch_tt(struct mu3h_sch_ep_info *sch_ep, bool used)

>  {

>  	struct mu3h_sch_tt *tt = sch_ep->sch_tt;

> -	u32 base, num_esit;

> -	int bw_updated;

> -	int bits;

> -	int i, j;

> -

> -	num_esit = XHCI_MTK_MAX_ESIT / sch_ep->esit;

> -	bits = (sch_ep->ep_type == ISOC_OUT_EP) ? sch_ep->cs_count : 1;

> +	int i, j, bw_updated;

> +	const int nr_lower_uframes =

> +		DIV_ROUND_UP(sch_ep->maxpkt, FS_PAYLOAD_MAX);

>  

>  	if (used)

>  		bw_updated = sch_ep->bw_cost_per_microframe;

>  	else

>  		bw_updated = -sch_ep->bw_cost_per_microframe;

>  

> -	for (i = 0; i < num_esit; i++) {

> -		base = sch_ep->offset + i * sch_ep->esit;

> -

> -		for (j = 0; j < bits; j++) {

> -			if (used)

> -				set_bit(base + j, tt->ss_bit_map);

> -			else

> -				clear_bit(base + j, tt->ss_bit_map);

> -		}

> -

> -		for (j = 0; j < sch_ep->cs_count; j++)

> -			tt->fs_bus_bw[base + j] += bw_updated;

> +	for (i = sch_ep->offset; i < XHCI_MTK_MAX_ESIT; i += sch_ep->esit) {

> +		for (j = 0; j < nr_lower_uframes; j++)

> +			tt->fs_bus_bw[i+ j + 1] += bw_updated;

>  	}

>  

>  	if (used)

> @@ -634,9 +604,11 @@ static int check_sch_bw(struct mu3h_sch_bw_info *sch_bw,

>  		if (min_bw > worst_bw) {

>  			min_bw = worst_bw;

>  			found = i;

> +			/* fastpath: bandwidth contributions to host is low

> +			 * when it's fs/ls */

> +			if (sch_ep->sch_tt || min_bw == 0)

> +				break;

>  		}

> -		if (min_bw == 0)

> -			break;

>  	}

>  

>  	/* check bandwidth */

> diff --git a/drivers/usb/host/xhci-mtk.h b/drivers/usb/host/xhci-mtk.h

> index 621ec1a85009..8a879f99ae1c 100644

> --- a/drivers/usb/host/xhci-mtk.h

> +++ b/drivers/usb/host/xhci-mtk.h

> @@ -20,12 +20,10 @@

>  #define XHCI_MTK_MAX_ESIT	64

>  

>  /**

> - * @ss_bit_map: used to avoid start split microframes overlay

>   * @fs_bus_bw: array to keep track of bandwidth already used for FS

>   * @ep_list: Endpoints using this TT

>   */

>  struct mu3h_sch_tt {

> -	DECLARE_BITMAP(ss_bit_map, XHCI_MTK_MAX_ESIT);

>  	u32 fs_bus_bw[XHCI_MTK_MAX_ESIT];

>  	struct list_head ep_list;

>  };