On Tue, Oct 27, 2020 at 11:15:24AM +0200, Felipe Balbi wrote:
>
> Hi,
>
> Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx> writes:
>
> > In accordance with [1] the DWC_usb3 core sets the GUSB2PHYACCn.VStsDone
> > bit when the PHY vendor control access is done and clears it when the
> > application initiates a new transaction. The doc doesn't say anything
> > about the GUSB2PHYACCn.VStsBsy flag serving for the same purpose. Moreover
> > we've discovered that the VStsBsy flag can be cleared before the VStsDone
> > bit. So using the former as a signal of the PHY control registers
> > completion might be dangerous. Let's have the VStsDone flag utilized
> > instead then.
> >
> > [1] Synopsys DesignWare Cores SuperSpeed USB 3.0 xHCI Host Controller
> > Databook, 2.70a, December 2013, p.388
> >
> > Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/usb/dwc3/core.h | 1 +
> > drivers/usb/dwc3/ulpi.c | 2 +-
> > 2 files changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> > index 2f04b3e42bf1..8d5e5bba1bc2 100644
> > --- a/drivers/usb/dwc3/core.h
> > +++ b/drivers/usb/dwc3/core.h
> > @@ -284,6 +284,7 @@
> >
> > /* Global USB2 PHY Vendor Control Register */
> > #define DWC3_GUSB2PHYACC_NEWREGREQ BIT(25)
> > +#define DWC3_GUSB2PHYACC_DONE BIT(24)
> > #define DWC3_GUSB2PHYACC_BUSY BIT(23)
> > #define DWC3_GUSB2PHYACC_WRITE BIT(22)
> > #define DWC3_GUSB2PHYACC_ADDR(n) (n << 16)
> > diff --git a/drivers/usb/dwc3/ulpi.c b/drivers/usb/dwc3/ulpi.c
> > index e6e6176386a4..20f5d9aba317 100644
> > --- a/drivers/usb/dwc3/ulpi.c
> > +++ b/drivers/usb/dwc3/ulpi.c
> > @@ -24,7 +24,7 @@ static int dwc3_ulpi_busyloop(struct dwc3 *dwc)
> >
> > while (count--) {
> > reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYACC(0));
> > - if (!(reg & DWC3_GUSB2PHYACC_BUSY))
> > + if (reg & DWC3_GUSB2PHYACC_DONE)
>
> are you sure this works in all supported versions of the core?
I can't be sure about that since I've got only the 2.70a version of the
core. But as I said in the patch log it was a bit incorrect to use the
BUSY flag here in the first place. So if there is no IP core peculiarity
here which had been workarounded by polling the BUSY-flag, then I'd stick
with the DONE-flag in the busy-loop. In the former case I'd suggest to add
a useful comment why the BUSY-flag is required to be polled though...
-Sergey
>
> John, could you confirm this for us?
>
> thanks
>
> --
> balbi
