On Thu, Sep 10, 2020 at 02:51:53PM +1200, Chris Packham wrote:
> The ehci controller found in some Broadcom switches with integrated SoCs
> has an issue which causes a soft lockup with large transfers like you
> see when running ext4 on USB3 flash drive.
>
> Port the fix from the Broadcom XLDK to increase the OUT_THRESHOLD to
> avoid the problem.
>
> Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
> ---
>
> I don't have much data on what this change does. I can say it is needed to
> avoid a soft lockup when using a USB3 Flash drive formatted has ext4 (USB2 +
> ext4 is OK, USB3 + fat is OK). I presume the affected combination ends up using
> larger transfers triggering the problem.
>
> The equivalent change in the Broadcom XLDK is
>
> if (IS_ENABLED(CONFIG_USB_EHCI_XGS_IPROC))
> ehci_writel(ehci, BCM_USB_FIFO_THRESHOLD,
> &ehci->regs->reserved4[6]);
>
> This is problematic because it would unconditionally apply to all ehci
> controllers whenever CONFIG_USB_EHCI_XGS_IPROC is enabled (also reserved4 only
> goes to 6 so technically it's indexing off the end of the array).
>
> I wasn't sure if I should add a new property or somehow detect the affected
> host controller. I settled on using of_device_is_compatible() as that seemed
> the simplest thing to do.
Reasonable.
> drivers/usb/host/ehci-platform.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/usb/host/ehci-platform.c b/drivers/usb/host/ehci-platform.c
> index 006c4f6188a5..0d2de8faa3c1 100644
> --- a/drivers/usb/host/ehci-platform.c
> +++ b/drivers/usb/host/ehci-platform.c
> @@ -53,6 +53,9 @@ struct ehci_platform_priv {
>
> static const char hcd_name[] = "ehci-platform";
>
> +#define bcm_iproc_insnreg01 hostpc
> +#define BCM_USB_FIFO_THRESHOLD 0x00800040
Minor nit: Since hostpc is nominally an array, IMO it would be a little
clearer to define bcm_iproc_insnreg01 as hostpc[0] and then do the
ehci_writel to &ehci->regs->bcm_iproc_insnreg01. That makes it look
more like an ordinary structure member.
Also IMO, it's better to put the #define's before the structure
definitions.
> +
> static int ehci_platform_reset(struct usb_hcd *hcd)
> {
> struct platform_device *pdev = to_platform_device(hcd->self.controller);
> @@ -358,6 +361,9 @@ static int ehci_platform_probe(struct platform_device *dev)
>
> device_wakeup_enable(hcd->self.controller);
> device_enable_async_suspend(hcd->self.controller);
> + if (of_device_is_compatible(dev->dev.of_node, "brcm,xgs-iproc-ehci"))
> + ehci_writel(ehci, BCM_USB_FIFO_THRESHOLD,
> + ehci->regs->bcm_iproc_insnreg01);
In theory, this should go before the usb_add_hcd() call because
afterward the controller is active. But you can't put it before
ehci->regs has been assigned, which happens in ehci_setup(). Probably
the best place is at the end of ehci_platform_reset().
Alan Stern
> platform_set_drvdata(dev, hcd);
>
> if (priv->quirk_poll)
> --
> 2.28.0
>
