Re: [PATCH 4/4] xHCI: Handle dwc3 erratum on USB3 HW LPM feature.

[Li Yang]

On Fri, Jan 5, 2018 at 4:00 AM Ran Wang <ran.wang_1@xxxxxxx> wrote:
>
> Synopsys STARS ticket: 90000969472(A-010131)
>
> Description: This erratum is applicable for the USB 3.0 Super
> Speed host mode operation. When the U2 timer expires while in
> U1 mode, the USB 3.0 controller completes a U1->U2 entry operation
> lasting three mac3_clk (24 ns). If the xHCI driver issues a
> U3 request during this operation, thecontroller drops this request.
>
> Impact: The controller ignores the request when the xHCI driver
> programs the U3 entry (PORTSC.PLS = U3).
>
> Workaround:
> 1. Before initiating U3 entry, save PORTPMSC.
> 2. Disable U2 entry by programming PORTPMSC[U2 Timeout] = h'FF.
> 3. After U3 entry, re-enable the U2 timer by programming PORTPMSC
> with the value saved in Step 1.

Hi Mathias,

Could you help to review this patch?

Hi Ran,

Since this is an dwc3 related hardware issue, can it be addressed in
the dwc3 layer instead of in the common xhci layer?

>
> Signed-off-by: Ran Wang <ran.wang_1@xxxxxxx>
> ---
>  drivers/usb/host/xhci-hub.c  |   22 ++++++++++++++++++++++
>  drivers/usb/host/xhci-plat.c |    6 +++++-
>  drivers/usb/host/xhci.h      |    1 +
>  3 files changed, 28 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index f070f94..a61185e 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -676,12 +676,34 @@ void xhci_set_link_state(struct xhci_hcd *xhci, __le32 __iomem **port_array,
>                                 int port_id, u32 link_state)
>  {
>         u32 temp;
> +       u32 portpmsc_u2_backup = 0;
> +
> +       /* Backup U2 timeout info before initiating U3 entry erratum A-010131 */
> +       if (xhci->shared_hcd->speed >= HCD_USB3 &&
> +                       link_state == USB_SS_PORT_LS_U3 &&
> +                       (xhci->quirks & XHCI_DIS_U1U2_WHEN_U3)) {
> +               portpmsc_u2_backup = readl(port_array[port_id] + PORTPMSC);
> +               portpmsc_u2_backup &= PORT_U2_TIMEOUT_MASK;
> +               temp = readl(port_array[port_id] + PORTPMSC);
> +               temp |= PORT_U2_TIMEOUT_MASK;
> +               writel(temp, port_array[port_id] + PORTPMSC);
> +       }
>
>         temp = readl(port_array[port_id]);
>         temp = xhci_port_state_to_neutral(temp);
>         temp &= ~PORT_PLS_MASK;
>         temp |= PORT_LINK_STROBE | link_state;
>         writel(temp, port_array[port_id]);
> +
> +       /* Restore U2 timeout info after U3 entry complete */
> +       if (xhci->shared_hcd->speed >= HCD_USB3 &&
> +                       link_state == USB_SS_PORT_LS_U3 &&
> +                       (xhci->quirks & XHCI_DIS_U1U2_WHEN_U3)) {
> +               temp = readl(port_array[port_id] + PORTPMSC);
> +               temp &= ~PORT_U2_TIMEOUT_MASK;
> +               temp |= portpmsc_u2_backup;
> +               writel(temp, port_array[port_id] + PORTPMSC);
> +       }
>  }
>
>  static void xhci_set_remote_wake_mask(struct xhci_hcd *xhci,
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 1969e56..616c56e 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -266,8 +266,12 @@ static int xhci_plat_probe(struct platform_device *pdev)
>         if (device_property_read_bool(sysdev, "usb2-lpm-disable"))
>                 xhci->quirks |= XHCI_HW_LPM_DISABLE;
>
> -       if (device_property_read_bool(sysdev, "usb3-lpm-capable"))
> +       if (device_property_read_bool(sysdev, "usb3-lpm-capable")) {
>                 xhci->quirks |= XHCI_LPM_SUPPORT;
> +               if (device_property_read_bool(sysdev,
> +                                       "snps,dis-u1u2-when-u3-quirk"))
> +                       xhci->quirks |= XHCI_DIS_U1U2_WHEN_U3;
> +       }
>
>         if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped"))
>                 xhci->quirks |= XHCI_BROKEN_PORT_PED;
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index b966cd8..9704779 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1835,6 +1835,7 @@ struct xhci_hcd {
>  /* Reserved. It was XHCI_U2_DISABLE_WAKE */
>  #define XHCI_ASMEDIA_MODIFY_FLOWCONTROL        (1 << 28)
>  #define XHCI_HW_LPM_DISABLE    (1 << 29)
> +#define XHCI_DIS_U1U2_WHEN_U3 (1 << 30)
>
>         unsigned int            num_active_eps;
>         unsigned int            limit_active_eps;
> --
> 1.7.1
>
> --
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