Re: FAILED: patch "[PATCH] PCI: dwc: Move interrupt acking into the proper callback" failed to apply to 4.14-stable tree

[Niklas Cassel <niklas.cassel@linaro.org>]

On Thu, Jan 17, 2019 at 09:58:43AM +0000, Marc Zyngier wrote:
> On 16/01/2019 23:43, Niklas Cassel wrote:
> > On Tue, Jan 15, 2019 at 09:24:37AM +0100, gregkh@linuxfoundation.org wrote:
> >>
> >> The patch below does not apply to the 4.14-stable tree.
> >> If someone wants it applied there, or to any other stable or longterm
> >> tree, then please email the backport, including the original git commit
> >> id to <stable@vger.kernel.org>.
> > 
> > Hello Marc,
> > 
> > You said that you were going to backport this to 4.14, right?
> 
> Me, or anyone else. Preferably someone who, like you, has the HW at hand (I don't).
> 
> > IIRC, you said something about creating a simple dw_pci_bottom_ack()
> > (since 4.14 lacks a ack() function).
> 
> Indeed. Something like this:
> 
> diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
> index bc3e2d8d0cce..f4f3eeee10af 100644
> --- a/drivers/pci/dwc/pcie-designware-host.c
> +++ b/drivers/pci/dwc/pcie-designware-host.c
> @@ -45,8 +45,19 @@ static int dw_pcie_wr_own_conf(struct pcie_port *pp, int where, int size,
>  	return dw_pcie_write(pci->dbi_base + where, size, val);
>  }
>  
> +static void dwc_irq_ack(struct irq_data *d)
> +{
> +	struct msi_desc *msi = irq_data_get_msi_desc(d);
> +	struct pcie_port *pp = msi_desc_to_pci_sysdata(msi);
> +	int pos = d->hwirq % 32;
> +	int i = d->hwirq / 32;
> +
> +	dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + i * 12, 4, BIT(pos));
> +}
> +

Thanks Marc.

This does not seem to work.
It appears that the ack function is never called.
I assume that this is because of:

irq_set_chip_and_handler(irq, &dw_msi_irq_chip, handle_simple_irq);

is it safe to simply change this to handle_edge_irq?
(Which seems to be the case after this after this driver's
MSI handling was heavily refactored in 4.17.)

I know that you were against reverting 8c934095fa2f ("PCI: dwc: Clear
MSI interrupt status after it is handled, not before") on mainline,
since that wouldn't hinder people from moving around stuff in the
future, but perhaps reverting this commit on 4.14 is safer than
changing the irq handler type?


Kind regards,
Niklas

>  static struct irq_chip dw_msi_irq_chip = {
>  	.name = "PCI-MSI",
> +	.irq_ack = dwc_irq_ack,
>  	.irq_enable = pci_msi_unmask_irq,
>  	.irq_disable = pci_msi_mask_irq,
>  	.irq_mask = pci_msi_mask_irq,
> @@ -72,8 +83,6 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
>  					    pos)) != 32) {
>  			irq = irq_find_mapping(pp->irq_domain, i * 32 + pos);
>  			generic_handle_irq(irq);
> -			dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + i * 12,
> -					    4, 1 << pos);
>  			pos++;
>  		}
>  	}
> 
> All I can say is that it compiles.
> 
> Thanks,
> 
> 	M.
> -- 
> Jazz is not dead. It just smells funny...