Re: [PATCH v2 2/5] PCI: dwc: Teach dwc core to parse additional MSI interrupts

[Bjorn Helgaas <helgaas@kernel.org>]

On Sat, Apr 23, 2022 at 04:39:36PM +0300, Dmitry Baryshkov wrote:
> DWC driver parses a single "msi" interrupt which gets fired when the EP
> sends an MSI interrupt, however for some devices (Qualcomm) devies MSI
> vectors are handled in groups of 32 vectors. Add support for parsing
> "split" MSI interrupts.

devies?  Maybe spurious?

> In addition to the "msi" interrupt, the code will lookup the "msi2",
> "msi3", etc. IRQs and use them for the MSI group interrupts. For
> backwards compatibility with existing DTS files, the code will not error
> out if any of these interrupts is missing. Instead it will limit itself
> to the amount of MSI group IRQs declared in the DT file.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 23 +++++++++++++++++++
>  drivers/pci/controller/dwc/pcie-designware.h  |  1 +
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 5d90009a0f73..ce7071095006 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -382,6 +382,29 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  				pp->msi_irq[0] = irq;
>  			}
>  
> +			if (pp->has_split_msi_irq) {
> +				char irq_name[] = "msiXXX";
> +				int irq;
> +
> +				for (ctrl = 1; ctrl < num_ctrls; ctrl++) {
> +					if (pp->msi_irq[ctrl])
> +						continue;
> +
> +					snprintf(irq_name, sizeof(irq_name), "msi%d", ctrl + 1);
> +					irq = platform_get_irq_byname_optional(pdev, irq_name);
> +					if (irq == -ENXIO) {
> +						num_ctrls = ctrl;
> +						pp->num_vectors = num_ctrls * MAX_MSI_IRQS_PER_CTRL;
> +						dev_warn(dev, "Limiting amount of MSI irqs to %d\n", pp->num_vectors);
> +						break;
> +					}
> +					if (irq < 0)
> +						return irq;
> +
> +					pp->msi_irq[ctrl] = irq;
> +				}
> +			}

This is getting pretty deeply nested, which means it's impractical to
fit in 80 columns like the rest of the file, which means it's ripe for
refactoring to reduce the indentation.

s/amount of/number of/
s/MSI irqs/MSI IRQs/

>  			pp->msi_irq_chip = &dw_pci_msi_bottom_irq_chip;
>  
>  			ret = dw_pcie_allocate_domains(pp);
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 9c1a38b0a6b3..3aa840a5b19c 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -179,6 +179,7 @@ struct dw_pcie_host_ops {
>  
>  struct pcie_port {
>  	bool			has_msi_ctrl:1;
> +	bool			has_split_msi_irq:1;
>  	u64			cfg0_base;
>  	void __iomem		*va_cfg0_base;
>  	u32			cfg0_size;
> -- 
> 2.35.1
>