Re: [PATCH V2] usb: xhci: add support for performing fake doorbell

From: Hauke Mehrtens
Date: Mon Oct 17 2016 - 17:10:41 EST


On 10/17/2016 10:30 PM, RafaÅ MiÅecki wrote:
> From: RafaÅ MiÅecki <rafal@xxxxxxxxxx>
>
> Broadcom's Northstar XHCI controllers seem to need a special start
> procedure to work correctly. There isn't any official documentation of
> this, the problem is that controller doesn't detect any connected
> devices with default setup. Moreover connecting USB device to controller
> that doesn't run properly can cause SoC's watchdog issues.
>
> A workaround that was successfully tested on multiple devices is to
> perform a fake doorbell. This patch adds code for doing this and enables
> it on BCM4708 family.
>
> Signed-off-by: RafaÅ MiÅecki <rafal@xxxxxxxxxx>
> ---
> V2: Enable quirk for brcm,bcm4708 machines instead of adding separated binding
> for it. Thanks Rob for your comment on this.
> ---
> drivers/usb/host/xhci-plat.c | 6 +++++
> drivers/usb/host/xhci.c | 63 +++++++++++++++++++++++++++++++++++++++++---
> drivers/usb/host/xhci.h | 1 +
> 3 files changed, 67 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index ed56bf9..b01a3be 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -56,12 +56,18 @@ static int xhci_priv_init_quirk(struct usb_hcd *hcd)
>
> static void xhci_plat_quirks(struct device *dev, struct xhci_hcd *xhci)
> {
> + struct platform_device *pdev = to_platform_device(dev);
> + struct device_node *node = pdev->dev.of_node;
> +
> /*
> * As of now platform drivers don't provide MSI support so we ensure
> * here that the generic code does not try to make a pci_dev from our
> * dev struct in order to setup MSI
> */
> xhci->quirks |= XHCI_PLAT;
> +
> + if (node && of_machine_is_compatible("brcm,bcm4708"))
> + xhci->quirks |= XHCI_FAKE_DOORBELL;

Are you sure only the bcm4708 and similar SoCs are affected? Having here
a list with 3 or more checks would looks strange. I prefer your first patch.

@Florian do you know if other Broadcom SoC are affected by this problem
or are only Northstar SoCs affected?

Hauke