On Tue, 15 May 2012, Marek Vasut wrote:
> Dear Alan Stern,
>
> > On Tue, 15 May 2012, Marek Vasut wrote:
> > > This comes handy on the i.MX28 CPU, where the host IRQ also signalises
> > > that the disconnection detector shall be enabled/disabled on the PHY.
> > >
> > > Signed-off-by: Marek Vasut <marex@xxxxxxx>
> > > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> > > Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> > > Cc: Felipe Balbi <balbi@xxxxxx>
> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > > Cc: Linux USB <linux-usb@xxxxxxxxxxxxxxx>
> > > ---
> > >
> > > drivers/usb/chipidea/host.c | 4 ++++
> > > include/linux/usb/chipidea.h | 1 +
> > > 2 files changed, 5 insertions(+)
> > >
> > > diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
> > > index 9eacd21..97bb167 100644
> > > --- a/drivers/usb/chipidea/host.c
> > > +++ b/drivers/usb/chipidea/host.c
> > > @@ -94,6 +94,10 @@ static const struct hc_driver ci_ehci_hc_driver = {
> > >
> > > static irqreturn_t host_irq(struct ci13xxx *ci)
> > > {
> > >
> > > + if (ci->udc_driver->notify_event)
> > > + ci->udc_driver->notify_event(ci,
> > > + CI13XXX_CONTROLLER_HOST_IRQ_EVENT);
> > > +
> > >
> > > return usb_hcd_irq(ci->irq, ci->hcd);
> > >
> > > }
> >
> > This is a rather roundabout way of doing things. Why add a new
> > notifier mechanism when you can simply register another interrupt
> > handler for the same IRQ?
>
> You certainly can, but how would you access the EHCI registers from PHY driver?
The same way you get informed about ci above: The information would get
passed to the interrupt handler.
> They have separate memory resources. Because the notifier passes data figured
> out by reading the EHCI register (USBSTS, PCD bit) and tells PHY to
> enable/disable the disconnection detector accordingly.
I'm not sure I really understand the purpose of all this. Why does the
PHY driver need to know about every IRQ the host driver receives?
Also, since the code above is part of a _host_ driver, why does it call
through a pointer in ci->udc_driver -- does that even make sense in a
host-only situation? And why can't it call the PHY driver directly?
Alan Stern
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