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

[Carl Huang]

On 2020-12-10 03:48, Jeffrey Hugo wrote:
> 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.
Host needs to program msi_data to QCA6390 hardware components(lots of 
standard
rings), and this msi_data is used to generate MSI interrupt.  If kernel 
has
re-assigned msi_data to QCA6390 when irq migration happens, and this 
re-assigned
msi_data is written to QCA6390 PCIe config space only, standard rings 
still use
previous msi_data.


> > > 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?
Yes. This patch involves MHI module, so send it separately.
There is another patch set for QCA6390 to support one MSI vector.

> > > 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?
Not sure if per irq manner is needed for others, but ath11k doesn't need
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.
Yes, will document this field in V2.

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