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usb: xhci-mtk: add only one extra CS for FS/LS INTR

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[ Upstream commit 1bf661daf6b084bc4d753f55b54f35dc98709685 ]

In USB2 Spec:
"11.18.5 TT Response Generation
In general, there will be two (or more) complete-split
transactions scheduled for a periodic endpoint.
However, for interrupt endpoints, the maximum size of
the full-/low-speed transaction guarantees that it can
never require more than two complete-split transactions.
Two complete-split transactions are only required
when the transaction spans a microframe boundary."

Due to the maxp is 64, and less then 188 (at most in one
microframe), seems never span boundary, so use only one CS
for FS/LS interrupt transfer, this will save some bandwidth.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/5b9ff09f53d23cf9e5c5437db4ffc18b798bf60c.1615170625.git.chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 548011957d1d ("usb: xhci-mtk: relax TT periodic bandwidth allocation")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Chunfeng Yun 2021-03-08 10:51:53 +08:00 committed by Greg Kroah-Hartman
parent b1e11bc66c
commit a2566a8dc5
1 changed files with 3 additions and 7 deletions
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10
drivers/usb/host/xhci-mtk-sch.c
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@ -408,13 +408,11 @@ static int check_sch_tt(struct usb_device *udev,
{
struct mu3h_sch_tt *tt = sch_ep->sch_tt;
u32 extra_cs_count;
u32 fs_budget_start;
u32 start_ss, last_ss;
u32 start_cs, last_cs;
int i;
start_ss = offset % 8;
fs_budget_start = (start_ss + 1) % 8;
if (sch_ep->ep_type == ISOC_OUT_EP) {
last_ss = start_ss + sch_ep->cs_count - 1;
@ -450,16 +448,14 @@ static int check_sch_tt(struct usb_device *udev,
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 = (fs_budget_start == 6) ? 1 : 2;
extra_cs_count = 1;
cs_count += extra_cs_count;
if (cs_count > 7)
cs_count = 7; /* HW limit */
for (i = 0; i < cs_count + 2; i++) {
if (test_bit(offset + i, tt->ss_bit_map))
return -ERANGE;
}
if (test_bit(offset, tt->ss_bit_map))
return -ERANGE;
sch_ep->cs_count = cs_count;
/* one for ss, the other for idle */