Re: [PATCH 3/3] PCI: designware: Move interrupt acking into the proper callback

[Marc Zyngier <marc.zyngier@arm.com>]

On Tue, 4 Dec 2018 15:50:32 +0530
Kishon Vijay Abraham I <kishon@ti.com> wrote:

> Hi,
> 
> On 14/11/18 4:27 AM, Marc Zyngier wrote:
> > The write to the status register is really an ACK for the HW,
> > and should be treated as such by the driver. Let's move it to the
> > irq_ack callback, which will prevent people from moving it around
> > in order to paper over other bugs.
> > 
> > Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-host.c | 13 +++++++------
> >  1 file changed, 7 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> > index 0a76948ed49e..f06e67c60593 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > @@ -99,9 +99,6 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
> >  					       (i * MAX_MSI_IRQS_PER_CTRL) +
> >  					       pos);
> >  			generic_handle_irq(irq);
> > -			dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS +
> > -						(i * MSI_REG_CTRL_BLOCK_SIZE),
> > -					    4, 1 << pos);
> >  			pos++;
> >  		}
> >  	}
> > @@ -200,14 +197,18 @@ static void dw_pci_bottom_unmask(struct irq_data *data)
> >  
> >  static void dw_pci_bottom_ack(struct irq_data *d)
> >  {
> > -	struct msi_desc *msi = irq_data_get_msi_desc(d);
> > -	struct pcie_port *pp;
> > +	struct pcie_port *pp  = irq_data_get_irq_chip_data(d);
> > +	unsigned int res, bit, ctrl;
> >  	unsigned long flags;
> >  
> > -	pp = msi_desc_to_pci_sysdata(msi);
> > +	ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
> > +	res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
> > +	bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
> >  
> >  	raw_spin_lock_irqsave(&pp->lock, flags);
> >  
> > +	dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + res, 4, 1 << bit);  
> 
> This register should be written only if msi_irq_ack callback is not populated
> similar to other dw_pci_bottom_*() functions.

Why? This was so far unconditionally written, and my understanding is
that without this write, no further MSI can be delivered.

What makes you think otherwise?

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