Re: [PATCH v8 2/6] usb: host: xhci: plat: Add suspend quirk for dwc3 controller

[Brian Norris <briannorris@chromium.org>]

Hi,

On Mon, Jun 28, 2021 at 05:38:13PM +0530, Sandeep Maheswaram wrote:
> During suspend read the status of all port and make sure the PHYs
> are in the correct mode based on current speed.
> Phy interrupt masks are set based on this mode. Keep track of the mode
> of the HS PHY to be able to configure wakeup properly.
> 
> Also check during suspend if any wakeup capable devices are
> connected to the controller (directly or through hubs), if there
> are none set a flag to indicate that the PHY should be powered
> down during suspend.

...

> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c

> @@ -430,6 +431,39 @@ static int xhci_plat_remove(struct platform_device *dev)
>  
>  	return 0;
>  }
> +static void xhci_dwc3_suspend_quirk(struct usb_hcd *hcd)

nit: you need a blank line above this (in between functions).

> +{
> +	int i, num_ports;
> +	u32 reg;
> +	unsigned int ss_phy_mode = 0;
> +	struct dwc3 *dwc = dev_get_drvdata(hcd->self.controller->parent);
> +	struct xhci_hcd	*xhci_hcd = hcd_to_xhci(hcd);
> +
> +	dwc->hs_phy_mode = 0;
> +
> +	reg = readl(&xhci_hcd->cap_regs->hcs_params1);
> +	num_ports = HCS_MAX_PORTS(reg);
> +
> +	for (i = 0; i < num_ports; i++) {
> +		reg = readl(&xhci_hcd->op_regs->port_status_base + i * 0x04);
> +		if (reg & PORT_PE) {
> +			if (DEV_HIGHSPEED(reg) || DEV_FULLSPEED(reg))
> +				dwc->hs_phy_mode |= PHY_MODE_USB_HOST_HS;
> +			else if (DEV_LOWSPEED(reg))
> +				dwc->hs_phy_mode |= PHY_MODE_USB_HOST_LS;
> +
> +			if (DEV_SUPERSPEED(reg))
> +				ss_phy_mode |= PHY_MODE_USB_HOST_SS;
> +		}
> +	}
> +	phy_set_mode(dwc->usb2_generic_phy, dwc->hs_phy_mode);
> +	phy_set_mode(dwc->usb3_generic_phy, ss_phy_mode);
> +
> +	if (usb_wakeup_enabled_descendants(hcd->self.root_hub))
> +		dwc->phy_power_off = false;
> +	else
> +		dwc->phy_power_off = true;
> +}

This series breaks USB across S3 suspend/resume on Rockchip RK3399 Gru
platforms. Those platforms do not support USB wake (they power off many
of the relevant IP blocks in S3), and they *require* reconfiguring the
PHY on resume, but usb_wakeup_enabled_descendants() is returning
non-zero. If I revert patch 3, things work again.

Perhaps that's a Rockchip bug (should such platforms be disabling all PM
wakeup capabilities for their child hubs/devices?), but I'd much
appreciate resolving that before merging such a regression.

This also may be a sign that usb_wakeup_enabled_descendants() isn't
really the precise condition you should be using, if other platforms
aren't accurately reflecting feature support status in here.

Brian

P.S. In case it matters, I'm noticing this because earlier versions of
your patches (which have the same problem) are merged in our downstream
Chromium kernel tree.