On Mon, 1 Aug 2016, Marc Ohlf wrote:
> In ehci_turn_off_all_ports() all EHCI port register bits
> (except the PORT_RWC_BITS) are set to zero.
Even the PORT_WRC_BITS are set to 0. Oddly enough, the way to set
those bits to 0 is to write a 1 to them (see Table 2-16 in the EHCI
spec).
> On some hardware, this can lead to an system hang,
> when ehci_port_power() accesses the already cleaned registers.
>
> This patch changes the order of cleanup.
> First call ehci_port_power() which respects the current bits in
> port status registers
> and afterwards cleanup the hard way by setting everything else to zero.
>
> Signed-off-by: Marc Ohlf <ohlf@xxxxxxxxxx>
> ---
> drivers/usb/host/ehci-hcd.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
> index a962b89..1e5f529 100644
> --- a/drivers/usb/host/ehci-hcd.c
> +++ b/drivers/usb/host/ehci-hcd.c
> @@ -332,11 +332,11 @@ static void ehci_turn_off_all_ports(struct ehci_hcd *ehci)
> int port = HCS_N_PORTS(ehci->hcs_params);
>
> while (port--) {
> - ehci_writel(ehci, PORT_RWC_BITS,
> - &ehci->regs->port_status[port]);
> spin_unlock_irq(&ehci->lock);
> ehci_port_power(ehci, port, false);
> spin_lock_irq(&ehci->lock);
> + ehci_writel(ehci, PORT_RWC_BITS,
> + &ehci->regs->port_status[port]);
> }
> }
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
This should be marked for the -stable kernels as well.
Alan Stern
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