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usb: dwc3: workaround: U1/U2 -> U0 transiton

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RTL revisions <1.83a have an issue where, depending
on the link partner, the USB link might do multiple
entry/exit of low power states before a transfer
takes place causing degraded throughput.

The suggested workaround is to clear bits
12:9 of DCTL register if we see a transition
from U1|U2 to U0 and only re-enable that on
a transfer complete IRQ and we have no pending
transfers on any of the enabled endpoints.

Signed-off-by: Felipe Balbi <balbi@ti.com>
This commit is contained in:
Felipe Balbi 2011-10-14 13:00:30 +03:00
parent d39ee7be2a
commit fae2b904aa
2 changed files with 76 additions and 2 deletions
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2
drivers/usb/dwc3/core.h
View file

@ -569,6 +569,7 @@ struct dwc3_hwparams {
* @regs_size: address space size
* @irq: IRQ number
* @num_event_buffers: calculated number of event buffers
* @u1u2: only used on revisions <1.83a for workaround
* @maximum_speed: maximum speed requested (mainly for testing purposes)
* @revision: revision register contents
* @mode: mode of operation
@ -614,6 +615,7 @@ struct dwc3 {
int irq;
u32 num_event_buffers;
u32 u1u2;
u32 maximum_speed;
u32 revision;
u32 mode;

76
drivers/usb/dwc3/gadget.c
View file

@ -1376,6 +1376,31 @@ static void dwc3_endpoint_transfer_complete(struct dwc3 *dwc,
dep->flags &= ~DWC3_EP_BUSY;
dep->res_trans_idx = 0;
}
/*
* WORKAROUND: This is the 2nd half of U1/U2 -> U0 workaround.
* See dwc3_gadget_linksts_change_interrupt() for 1st half.
*/
if (dwc->revision < DWC3_REVISION_183A) {
u32 reg;
int i;
for (i = 0; i < DWC3_ENDPOINTS_NUM; i++) {
struct dwc3_ep *dep = dwc->eps[i];
if (!(dep->flags & DWC3_EP_ENABLED))
continue;
if (!list_empty(&dep->req_queued))
return;
}
reg = dwc3_readl(dwc->regs, DWC3_DCTL);
reg |= dwc->u1u2;
dwc3_writel(dwc->regs, DWC3_DCTL, reg);
dwc->u1u2 = 0;
}
}
static void dwc3_gadget_start_isoc(struct dwc3 *dwc,
@ -1794,8 +1819,55 @@ static void dwc3_gadget_wakeup_interrupt(struct dwc3 *dwc)
static void dwc3_gadget_linksts_change_interrupt(struct dwc3 *dwc,
unsigned int evtinfo)
{
/* The fith bit says SuperSpeed yes or no. */
dwc->link_state = evtinfo & DWC3_LINK_STATE_MASK;
enum dwc3_link_state next = evtinfo & DWC3_LINK_STATE_MASK;
/*
* WORKAROUND: DWC3 Revisions <1.83a have an issue which, depending
* on the link partner, the USB session might do multiple entry/exit
* of low power states before a transfer takes place.
*
* Due to this problem, we might experience lower throughput. The
* suggested workaround is to disable DCTL[12:9] bits if we're
* transitioning from U1/U2 to U0 and enable those bits again
* after a transfer completes and there are no pending transfers
* on any of the enabled endpoints.
*
* This is the first half of that workaround.
*
* Refers to:
*
* STAR#9000446952: RTL: Device SS : if U1/U2 ->U0 takes >128us
* core send LGO_Ux entering U0
*/
if (dwc->revision < DWC3_REVISION_183A) {
if (next == DWC3_LINK_STATE_U0) {
u32 u1u2;
u32 reg;
switch (dwc->link_state) {
case DWC3_LINK_STATE_U1:
case DWC3_LINK_STATE_U2:
reg = dwc3_readl(dwc->regs, DWC3_DCTL);
u1u2 = reg & (DWC3_DCTL_INITU2ENA
| DWC3_DCTL_ACCEPTU2ENA
| DWC3_DCTL_INITU1ENA
| DWC3_DCTL_ACCEPTU1ENA);
if (!dwc->u1u2)
dwc->u1u2 = reg & u1u2;
reg &= ~u1u2;
dwc3_writel(dwc->regs, DWC3_DCTL, reg);
break;
default:
/* do nothing */
break;
}
}
}
dwc->link_state = next;
dev_vdbg(dwc->dev, "%s link %d\n", __func__, dwc->link_state);
}