[PATCH 5.19 131/155] usb: xhci-mtk: relax TT periodic bandwidth allocation

Greg Kroah-Hartman
2022-09-06T14:17:12Z

From: Chunfeng Yun <chunfeng.yun@mediatek.com>

commit 8b13ea05117ffad4727b0971ed09122d5c91c4dc upstream.

Currently uses the worst case byte budgets on FS/LS bus bandwidth,
for example, for an isochronos IN endpoint with 192 bytes budget, it
will consume the whole 5 uframes(188 * 5) while the actual FS bus
budget should be just 192 bytes. It cause that many usb audio headsets
with 3 interfaces (audio input, audio output, and HID) cannot be
configured.
To improve it, changes to use "approximate" best case budget for FS/LS
bandwidth management. For the same endpoint from the above example,
the approximate best case budget is now reduced to (188 * 2) bytes.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/20220819080556.32215-1-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/host/xhci-mtk-sch.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)

--- a/drivers/usb/host/xhci-mtk-sch.c
+++ b/drivers/usb/host/xhci-mtk-sch.c
@@ -425,7 +425,6 @@ static int check_fs_bus_bw(struct mu3h_s

static int check_sch_tt(struct mu3h_sch_ep_info *sch_ep, u32 offset)
{
- u32 extra_cs_count;
u32 start_ss, last_ss;
u32 start_cs, last_cs;

@@ -461,18 +460,12 @@ static int check_sch_tt(struct mu3h_sch_
if (last_cs > 7)
return -ESCH_CS_OVERFLOW;

- if (sch_ep->ep_type == ISOC_IN_EP)
- extra_cs_count = (last_cs == 7) ? 1 : 2;
- else /* ep_type : INTR IN / INTR OUT */
- extra_cs_count = 1;
-
- cs_count += extra_cs_count;
if (cs_count > 7)
cs_count = 7; /* HW limit */

sch_ep->cs_count = cs_count;
- /* one for ss, the other for idle */
- sch_ep->num_budget_microframes = cs_count + 2;
+ /* ss, idle are ignored */
+ sch_ep->num_budget_microframes = cs_count;

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