On Fri, 5 Aug 2011, River Wang wrote:
> Sorry for missing diffstat line.
> ---------------------------------------------------------------
> From: Wang Zhi <zhi.wang@xxxxxxxxxxxxx>
> Date: Thu, 04 Aug 2011 21:51:57 -0700
> Subject: [PATCH]: USB: EHCI: Do not rely on PORT_SUSPEND to stop USB
> resuming in ehci_bus_resume().
>
> From EHCI Spec p.28 HC should clear PORT_SUSPEND when SW clears
> PORT_RESUME. In Intel Oaktrail platform, MPH (Multi-Port Host
> Controller) core clears PORT_SUSPEND directly when SW sets PORT_RESUME
> bit. If we rely on PORT_SUSPEND bit to stop USB resume, we will miss
> the action of clearing PORT_RESUME. This will cause unexpected long
> resume signal on USB bus.
>
> Signed-off-by: Wang Zhi <zhi.wang@xxxxxxxxxxxxx>
Basically okay, but see below.
> ---
> ehci-hub.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c
> index ea6184b..2f6cf9b 100644
> --- a/drivers/usb/host/ehci-hub.c
> +++ b/drivers/usb/host/ehci-hub.c
> @@ -343,7 +343,7 @@ static int ehci_bus_resume (struct usb_hcd *hcd)
> u32 temp;
> u32 power_okay;
> int i;
> - u8 resume_needed = 0;
> + unsigned long resume_needed = 0;
>
> if (time_before (jiffies, ehci->next_statechange))
> msleep(5);
> @@ -416,7 +416,7 @@ static int ehci_bus_resume (struct usb_hcd *hcd)
> if (test_bit(i, &ehci->bus_suspended) &&
> (temp & PORT_SUSPEND)) {
> temp |= PORT_RESUME;
> - resume_needed = 1;
> + set_bit(i, &resume_needed);
> }
> ehci_writel(ehci, temp, &ehci->regs->port_status [i]);
> }
> @@ -432,7 +432,7 @@ static int ehci_bus_resume (struct usb_hcd *hcd)
> while (i--) {
> temp = ehci_readl(ehci, &ehci->regs->port_status [i]);
> if (test_bit(i, &ehci->bus_suspended) &&
> - (temp & PORT_SUSPEND)) {
> + test_bit(i, &resume_needed)) {
You should remove the test_bit(i, &ehci->bus_suspended). The i bit
won't be set in resume_needed if it isn't also set in bus_suspended.
> temp &= ~(PORT_RWC_BITS | PORT_RESUME);
> ehci_writel(ehci, temp, &ehci->regs->port_status [i]);
> ehci_vdbg (ehci, "resumed port %d\n", i + 1);
Alan Stern
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