diff options
| author | John Youn <johnyoun@synopsys.com> | 2016-05-19 17:26:12 -0700 |
|---|---|---|
| committer | Felipe Balbi <felipe.balbi@linux.intel.com> | 2016-06-20 12:32:44 +0300 |
| commit | 32db3d9437b6bd560daeef82a8325436a4ac3366 (patch) | |
| tree | 6ca6932e39750d5de1f013cef4904c25b290b40f /drivers | |
| parent | 89bc856e5a7462e47d90d5a3f5396bd5795efd0c (diff) | |
usb: dwc3: gadget: Account for max size in TRB space
The current calculation takes dep->trb_dequeue - dep->trb_enqueue to
find the TRB space left.
If you enqueue 1, that results in:
(u8) 0 - (u8) 1 = 0xff = 255 TRBs left.
This is correct if DWC3_TRB_NUM == 256.
If DWC3_TRB_NUM is less than 256 (but still a power of 2) you need to
mod the result by DWC3_TRB_NUM.
For example the same calculation with DWC3_TRB_NUM = 8, results in:
255 % 6 = 7 TRBs left.
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/usb/dwc3/gadget.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 663ea9ed5993..4dea3e08f95c 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -845,6 +845,7 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep, static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep) { struct dwc3_trb *tmp; + u8 trbs_left; /* * If enqueue & dequeue are equal than it is either full or empty. @@ -864,7 +865,10 @@ static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep) return DWC3_TRB_NUM - 1; } - return dep->trb_dequeue - dep->trb_enqueue; + trbs_left = dep->trb_dequeue - dep->trb_enqueue; + trbs_left %= DWC3_TRB_NUM; + + return trbs_left; } static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep, |