Re: [PATCH] mhi: use irq_flags if client driver configures it

[Jeffrey Hugo]

On 12/9/2020 11:34 AM, Hemant Kumar wrote:
> On 12/7/20 7:55 PM, Carl Huang wrote:
> > If client driver has specified the irq_flags, mhi uses this specified
> > irq_flags. Otherwise, mhi uses default irq_flags.
> >
> > The purpose of this change is to support one MSI vector for QCA6390.
> > MHI will use one same MSI vector too in this scenario.
> >
> > In case of one MSI vector, IRQ_NO_BALANCING is needed when irq handler
> > is requested. The reason is if irq migration happens, the msi_data may
> > change too. However, the msi_data is already programmed to QCA6390
> > hardware during initialization phase. This msi_data inconsistence will
> > result in crash in kernel.

I'm confused as to how this happens.

> > Another issue is in case of one MSI vector, IRQF_NO_SUSPEND will trigger
> > WARNINGS because QCA6390 wants to disable the IRQ during the suspend.
> >
> > To avoid above two issues, QCA6390 driver specifies the irq_flags in case
> > of one MSI vector when mhi_register_controller is called.

Surely this change should be in a series where there is a following 
change which updates the QCA6390 driver?

> > Signed-off-by: Carl Huang <cjhuang@xxxxxxxxxxxxxx>
> > ---
> >   drivers/bus/mhi/core/init.c | 9 +++++++--
> >   include/linux/mhi.h         | 1 +
> >   2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
> > index 0ffdebd..5f74e1e 100644
> > --- a/drivers/bus/mhi/core/init.c
> > +++ b/drivers/bus/mhi/core/init.c
> > @@ -148,12 +148,17 @@ int mhi_init_irq_setup(struct mhi_controller 
> > *mhi_cntrl)
> >   {
> >       struct mhi_event *mhi_event = mhi_cntrl->mhi_event;
> >       struct device *dev = &mhi_cntrl->mhi_dev->dev;
> > +    unsigned long irq_flags = IRQF_SHARED | IRQF_NO_SUSPEND;
> >       int i, ret;
> > +    /* if client driver has set irq_flags, use it */
> > +    if (mhi_cntrl->irq_flags)
> > +        irq_flags = mhi_cntrl->irq_flags;
> Jeff if i remember correctly your use case also have one dedicated irq 
> line for all the MSIs, just want to confirm if you are fine with this 
> change ? i was wondering if any input check is required for irq_flags 
> passed by controller, or responsibility is on controller for any 
> undesired behavior. Like passing IRQF_SHARED and IRQF_ONESHOT when one 
> irq line is shared among multiple MSIs.

This feels a bit weird to me, but I don't think it'll cause a problem.

If we are allowing the controller to specify flags, should they be in a 
per irq manner?

> > +
> >       /* Setup BHI_INTVEC IRQ */
> >       ret = request_threaded_irq(mhi_cntrl->irq[0], mhi_intvec_handler,
> >                      mhi_intvec_threaded_handler,
> > -                   IRQF_SHARED | IRQF_NO_SUSPEND,
> > +                   irq_flags,
> >                      "bhi", mhi_cntrl);
> >       if (ret)
> >           return ret;
> > @@ -171,7 +176,7 @@ int mhi_init_irq_setup(struct mhi_controller 
> > *mhi_cntrl)
> >           ret = request_irq(mhi_cntrl->irq[mhi_event->irq],
> >                     mhi_irq_handler,
> > -                  IRQF_SHARED | IRQF_NO_SUSPEND,
> > +                  irq_flags,
> >                     "mhi", mhi_event);
> >           if (ret) {
> >               dev_err(dev, "Error requesting irq:%d for ev:%d\n",
> > diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> > index d4841e5..f039e58 100644
> > --- a/include/linux/mhi.h
> > +++ b/include/linux/mhi.h
> > @@ -442,6 +442,7 @@ struct mhi_controller {
> >       bool fbc_download;
> >       bool pre_init;
> >       bool wake_set;
> > +    unsigned long irq_flags;

You don't document this.  That gets a NACK from me.

> >   };
> >   /**
>
> Thanks,
> Hemant


--
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.