Re: [PATCH 30/39] PCI: Bulk conversion to generic_handle_domain_irq()

[Marc Zyngier <maz@kernel.org>]

On Mon, 24 May 2021 14:28:42 +0100,
Rob Herring <robh@kernel.org> wrote:
> 
> On Mon, May 24, 2021 at 3:38 AM Marc Zyngier <maz@kernel.org> wrote:
> >
> > On Thu, 20 May 2021 18:47:06 +0100,
> > Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Thu, May 20, 2021 at 11:57 AM Marc Zyngier <maz@kernel.org> wrote:
> > > >
> > > > Wherever possible, replace constructs that match either
> > > > generic_handle_irq(irq_find_mapping()) or
> > > > generic_handle_irq(irq_linear_revmap()) to a single call to
> > > > generic_handle_domain_irq().
> > > >
> > > > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > > > ---
> > > >  drivers/pci/controller/dwc/pci-dra7xx.c        | 14 +++++---------
> > > >  drivers/pci/controller/dwc/pci-keystone.c      |  5 ++---
> > > >  .../pci/controller/dwc/pcie-designware-host.c  |  9 ++++-----
> > > >  drivers/pci/controller/dwc/pcie-uniphier.c     |  6 ++----
> > > >  .../controller/mobiveil/pcie-mobiveil-host.c   | 15 ++++++---------
> > > >  drivers/pci/controller/pci-aardvark.c          |  5 ++---
> > > >  drivers/pci/controller/pci-ftpci100.c          |  2 +-
> > > >  drivers/pci/controller/pci-tegra.c             |  8 +++-----
> > > >  drivers/pci/controller/pci-xgene-msi.c         |  9 +++------
> > > >  drivers/pci/controller/pcie-altera-msi.c       | 10 ++++------
> > > >  drivers/pci/controller/pcie-altera.c           | 10 ++++------
> > > >  drivers/pci/controller/pcie-brcmstb.c          |  9 ++++-----
> > > >  drivers/pci/controller/pcie-iproc-msi.c        |  4 +---
> > > >  drivers/pci/controller/pcie-mediatek-gen3.c    | 13 ++++---------
> > > >  drivers/pci/controller/pcie-mediatek.c         | 12 ++++--------
> > > >  drivers/pci/controller/pcie-microchip-host.c   | 18 +++++++-----------
> > > >  drivers/pci/controller/pcie-rcar-host.c        |  8 +++-----
> > > >  drivers/pci/controller/pcie-rockchip-host.c    |  8 +++-----
> > > >  drivers/pci/controller/pcie-xilinx-cpm.c       |  4 ++--
> > > >  drivers/pci/controller/pcie-xilinx-nwl.c       | 13 +++----------
> > > >  drivers/pci/controller/pcie-xilinx.c           |  9 ++++-----
> > > >  21 files changed, 71 insertions(+), 120 deletions(-)
> > >
> > >
> > > > diff --git a/drivers/pci/controller/pci-xgene-msi.c b/drivers/pci/controller/pci-xgene-msi.c
> > > > index 1c34c897a7e2..cf3832b905e8 100644
> > > > --- a/drivers/pci/controller/pci-xgene-msi.c
> > > > +++ b/drivers/pci/controller/pci-xgene-msi.c
> > > > @@ -291,8 +291,7 @@ static void xgene_msi_isr(struct irq_desc *desc)
> > > >         struct irq_chip *chip = irq_desc_get_chip(desc);
> > > >         struct xgene_msi_group *msi_groups;
> > > >         struct xgene_msi *xgene_msi;
> > > > -       unsigned int virq;
> > > > -       int msir_index, msir_val, hw_irq;
> > > > +       int msir_index, msir_val, hw_irq, ret;
> > > >         u32 intr_index, grp_select, msi_grp;
> > > >
> > > >         chained_irq_enter(chip, desc);
> > > > @@ -330,10 +329,8 @@ static void xgene_msi_isr(struct irq_desc *desc)
> > > >                          * CPU0
> > > >                          */
> > > >                         hw_irq = hwirq_to_canonical_hwirq(hw_irq);
> > > > -                       virq = irq_find_mapping(xgene_msi->inner_domain, hw_irq);
> > > > -                       WARN_ON(!virq);
> > > > -                       if (virq != 0)
> > > > -                               generic_handle_irq(virq);
> > > > +                       ret = generic_handle_domain_irq(xgene_msi->inner_domain, hw_irq);
> > > > +                       WARN_ON(ret);
> > >
> > > There's various error prints in some of the handlers. I think they
> > > should be moved to the core. I can't imagine handling the irq is ever
> > > optional.
> >
> > Printing stuff like this is a sure recipe for disaster, and there is
> > no way I'm moving such crap into core code.
> 
> Then why maintain such crap code? I'm fine with just removing. I just
> think we should have some consistency.

Then by any mean, remove it. I'd even be tempted to say "remove the
driver", but there is an XGene-1 box right behind me...

> 
> > If the interrupt handling
> > fails (most likely because there is no mapping for this interrupt), it
> > is the driver's responsibility to handle the error (either disabling
> > the input or the output of the secondary irqchip). There isn't much
> > the core code can do about it.
> 
> I would imagine the errors here would be the 'this should never
> happen' kind. Maybe a race with tearing down the domain. Seems to me
> the core code should be warning when the calling code has made
> mistakes.

The core code already returns an error, which is plenty. It doesn't
have the context to actually *do* anything, and I don't think moaning
on the console helps much.

The onus is firmly on the caller side to get their act together.

	M.

-- 
Without deviation from the norm, progress is not possible.