RE: [PATCH v2 2/2] usb: dwc3: Add workaround for host mode VBUS glitch when boot

[Ran Wang]

Hi Leo,

> -----Original Message-----
> From: Yang Li <pku.leo@xxxxxxxxx>
> Sent: Tuesday, February 26, 2019 05:29
> To: Ran Wang <ran.wang_1@xxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Rob Herring
> <robh+dt@xxxxxxxxxx>; Mark Rutland <mark.rutland@xxxxxxx>; Felipe Balbi
> <balbi@xxxxxxxxxx>; linux-usb@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 2/2] usb: dwc3: Add workaround for host mode VBUS
> glitch when boot
> 
> On Tue, Feb 19, 2019 at 1:24 AM Ran Wang <ran.wang_1@xxxxxxx> wrote:
> >
> > When DWC3 is set to host mode by programming register DWC3_GCTL, VBUS
> > (or its control signal) will be turned on immediately on related Root
> > Hub ports. Then, the VBUS is turned off for a little while(15us) when
> > do xhci reset (conducted by xhci driver) and back to normal finally,
> > we can observe a negative glitch of related signal happen.
> >
> > This VBUS glitch might cause some USB devices enumeration fail if
> > kernel boot with them connected. Such as
> > LS1012AFWRY/LS1043ARDB/LX2160AQDS /LS1088ARDB with Kingston 16GB
> > USB2.0/Kingston USB3.0/JetFlash Transcend 4GB USB2.0 drives. The fail
> > cases include enumerated as full-speed device or report wrong device
> descriptor, etc.
> >
> > One SW workaround which can fix this is by programing all xhci
> > PORTSC[PP] to 0 to turn off VBUS immediately after setting host mode
> > in DWC3 driver (per signal measurement result, it will be too late to
> > do it in xhci-plat.c or xhci.c). Then, after xhci reset complete in
> > xhci driver, PORTSC[PP]s' value will back to 1 automatically and VBUS
> > on at that time, no glitch happen and normal enumeration process has no
> impact.
> >
> > Signed-off-by: Ran Wang <ran.wang_1@xxxxxxx>
> > ---
> > Changes in v2:
> >   - Rename related property to 'snps,host-vbus-glitches'
> >   - Rename related dwc member to 'host_vbus_glitches'
> >   - Add member 'host_vbus_glitches' description in 'dwc3'
> >
> >  drivers/usb/dwc3/core.c |   47
> +++++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/usb/dwc3/core.h |   12 +++++++++++-
> >  2 files changed, 58 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c index
> > a1b126f..02d11bc 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -100,6 +100,41 @@ static int dwc3_get_dr_mode(struct dwc3 *dwc)
> >         return 0;
> >  }
> >
> > +/*
> > + * dwc3_power_of_all_roothub_ports - Power off all Root hub ports
> > + * @dwc3: Pointer to our controller context structure  */ static void
> > +dwc3_power_off_all_roothub_ports(struct dwc3 *dwc) {
> > +       int i, port_num;
> > +       u32 reg, op_regs_base, offset;
> > +       void __iomem            *xhci_regs;
> > +
> > +       /* xhci regs is not mapped yet, do it temperary here */
> > +       if (dwc->xhci_resources[0].start) {
> > +               xhci_regs = ioremap(dwc->xhci_resources[0].start,
> > +                               DWC3_XHCI_REGS_END);
> > +               if (IS_ERR(xhci_regs)) {
> > +                       dev_err(dwc->dev, "Failed to ioremap xhci_regs\n");
> > +                       return;
> > +               }
> > +
> > +               op_regs_base = HC_LENGTH(readl(xhci_regs));
> > +               reg = readl(xhci_regs + XHCI_HCSPARAMS1);
> > +               port_num = HCS_MAX_PORTS(reg);
> > +
> > +               for (i = 1; i <= port_num; i++) {
> > +                       offset = op_regs_base + XHCI_PORTSC_BASE +
> > + 0x10*(i-1);
> 
> Define the 0x10 as macro?  And why don't you have the initial value of i loop to
> be 0 to avoid the (i-1) here?

OK, thanks for pointing out.

> > +                       reg = readl(xhci_regs + offset);
> > +                       reg &= ~PORT_POWER;
> > +                       writel(reg, xhci_regs + offset);
> > +               }
> > +
> > +               iounmap(xhci_regs);
> > +       } else
> > +               dev_err(dwc->dev, "xhci base reg invalid\n"); }
> > +
> >  void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)  {
> >         u32 reg;
> > @@ -109,6 +144,15 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)
> >         reg |= DWC3_GCTL_PRTCAPDIR(mode);
> >         dwc3_writel(dwc->regs, DWC3_GCTL, reg);
> >
> > +       /*
> > +        * We have to power off all Root hub ports immediately after DWC3 set
> > +        * to host mode to avoid VBUS glitch happen when xhci get reset later.
> > +        */
> > +       if (dwc->host_vbus_glitches) {
> > +               if (mode == DWC3_GCTL_PRTCAP_HOST)
> > +                       dwc3_power_off_all_roothub_ports(dwc);
> > +       }
> > +
> >         dwc->current_dr_role = mode;
> >  }
> >
> > @@ -1306,6 +1350,9 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> >         dwc->dis_metastability_quirk = device_property_read_bool(dev,
> >                                 "snps,dis_metastability_quirk");
> >
> > +       dwc->host_vbus_glitches = device_property_read_bool(dev,
> > +                               "snps,host-vbus-glitches");
> > +
> >         dwc->lpm_nyet_threshold = lpm_nyet_threshold;
> >         dwc->tx_de_emphasis = tx_de_emphasis;
> >
> > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h index
> > df87641..9b3a7ed 100644
> > --- a/drivers/usb/dwc3/core.h
> > +++ b/drivers/usb/dwc3/core.h
> > @@ -606,6 +606,14 @@
> >  #define DWC3_OSTS_VBUSVLD              BIT(1)
> >  #define DWC3_OSTS_CONIDSTS             BIT(0)
> >
> > +/* Partial XHCI Register and Bit fields for quirk */
> > +#define XHCI_HCSPARAMS1                0x4
> > +#define XHCI_PORTSC_BASE       0x400
> > +#define PORT_POWER                     (1 << 9)
> > +#define HCS_MAX_PORTS(p)       (((p) >> 24) & 0x7f)
> > +#define XHCI_HC_LENGTH(p)      (((p)>>00)&0x00ff)
> > +#define HC_LENGTH(p)           XHCI_HC_LENGTH(p)
> > +
> >  /* Structures */
> >
> >  struct dwc3_trb;
> > @@ -1024,6 +1032,8 @@ struct dwc3_scratchpad_array {
> >   *     2       - No de-emphasis
> >   *     3       - Reserved
> >   * @dis_metastability_quirk: set to disable metastability quirk.
> > + * @host-vbus-glitches: set to avoid vbus glitch during
> > + *                      xhci reset.
> >   * @imod_interval: set the interrupt moderation interval in 250ns
> >   *                 increments or 0 to disable.
> >   */
> > @@ -1209,6 +1219,7 @@ struct dwc3 {
> >         unsigned                tx_de_emphasis:2;
> >
> >         unsigned                dis_metastability_quirk:1;
> > +       unsigned                host_vbus_glitches:1;
> >
> >         u16                     imod_interval;
> >  };
> > @@ -1217,7 +1228,6 @@ struct dwc3 {
> >  #define INCRX_UNDEF_LENGTH_BURST_MODE 1
> >
> >  #define work_to_dwc(w)         (container_of((w), struct dwc3, drd_work))
> > -
> 
> No need to remove the new line here.
 
OK, will fix it in next version patch

Regards,
Ran
> >  /*
> > ----------------------------------------------------------------------
> > ---- */
> >
> >  struct dwc3_event_type {
> > --
> > 1.7.1
> >
> 
>