Hi, On Wed, Jan 14, 2015 at 03:06:39PM -0500, Alan Stern wrote: > > > This patch fixes bug described here: > > > https://lkml.org/lkml/2014/12/22/185 > > > > > > Signed-off-by: Robert Baldyga <r.baldyga@xxxxxxxxxxx> > > > --- > > > > > > Changelog: > > > > > > v2: > > > - fixed comment from Paul Zimmerman > > > > > > v1: https://lkml.org/lkml/2015/1/13/186 > > > > > > drivers/usb/dwc2/core_intr.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/usb/dwc2/core_intr.c b/drivers/usb/dwc2/core_intr.c > > > index ad43c5b..02e3e2d 100644 > > > --- a/drivers/usb/dwc2/core_intr.c > > > +++ b/drivers/usb/dwc2/core_intr.c > > > @@ -476,13 +476,13 @@ irqreturn_t dwc2_handle_common_intr(int irq, void *dev) > > > u32 gintsts; > > > irqreturn_t retval = IRQ_NONE; > > > > > > + spin_lock(&hsotg->lock); > > > + > > > if (!dwc2_is_controller_alive(hsotg)) { > > > > This is really, really odd. Register accesses are atomic, so the lock > > isn't really doing anything. Besides, you're calling > > dwc2_is_controller_alive() from within the IRQ handler, so IRQs are > > already disabled. > > Spinlocks sometimes do more than you think. For instance, here the > lock prevents the register access from happening while some other CPU > is holding the lock. If a silicon quirk causes the register access to > interfere with other activities, this could be important. readl() (which is used by dwc2_is_controller_alive()) adds a memory barrier to the register accesses, that should force all register accesses the be correctly ordered. I fail to see how a silicon quirk could cause this and if, indeed, it does, I'd be more comfortable with a proper STARS tickect number from synopsys :-s Then again, I don't even have a device with this controller and it seems to only be a problem with Robert's setup, so maybe it's a silicon bug caused by whoever integrated dwc2 in his silicon. -- balbi
Attachment:
signature.asc
Description: Digital signature
