On Thu, 19 May 2016, Srinivas Kandagatla wrote:
> This patch protects system from crashing at shutdown in
> cases where usb host is not added yet from OTG controller driver.
> As ehci_setup() not done yet, so stop accessing registers or
> variables initialized as part of ehci_setup().
>
> The use case is simple, for boards like DB410c where the usb host
> or device functionality is decided based on the micro-usb cable
> presence. If the board boots up with micro-usb connected, the
> OTG driver like echi-msm would not add the usb host by default.
> However a system shutdown would go and access registers and
> uninitialized variables, resulting in below crash.
...
> Fixes 4bb3cad7125b ("usb: host: ehci-msm: Register usb shutdown function")
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> ---
> drivers/usb/host/ehci-hcd.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
> index ae1b6e6..a962b89 100644
> --- a/drivers/usb/host/ehci-hcd.c
> +++ b/drivers/usb/host/ehci-hcd.c
> @@ -368,6 +368,15 @@ static void ehci_shutdown(struct usb_hcd *hcd)
> {
> struct ehci_hcd *ehci = hcd_to_ehci(hcd);
>
> + /**
> + * Protect the system from crashing at system shutdown in cases where
> + * usb host is not added yet from OTG controller driver.
> + * As ehci_setup() not done yet, so stop accessing registers or
> + * variables initialized in ehci_setup()
> + */
> + if (!ehci->sbrn)
> + return;
> +
> spin_lock_irq(&ehci->lock);
> ehci->shutdown = true;
> ehci->rh_state = EHCI_RH_STOPPING;
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
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