Re: [PATCH v11 3/7] PCI: dwc: Handle MSIs routed to multiple GIC interrupts

[Johan Hovold <johan@kernel.org>]

On Fri, May 20, 2022 at 09:31:10PM +0300, Dmitry Baryshkov wrote:
> On some of Qualcomm platforms each group of 32 MSI vectors is routed to the
> separate GIC interrupt. Implement support for such configurations by
> parsing "msi0" ... "msiN" interrupts and attaching them to the chained
> handler.
> 
> Note, that if DT doesn't list an array of MSI interrupts and uses single
> "msi" IRQ, the driver will limit the amount of supported MSI vectors
> accordingly (to 32).
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 58 +++++++++++++++++--
>  1 file changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index a076abe6611c..381bc24d5715 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -288,6 +288,43 @@ static void dw_pcie_msi_init(struct pcie_port *pp)
>  	dw_pcie_writel_dbi(pci, PCIE_MSI_ADDR_HI, upper_32_bits(msi_target));
>  }
>  
> +static const char * const split_msi_names[] = {
> +	"msi0", "msi1", "msi2", "msi3",
> +	"msi4", "msi5", "msi6", "msi7",
> +};
> +
> +static int dw_pcie_parse_split_msi_irq(struct pcie_port *pp)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct device *dev = pci->dev;
> +	struct platform_device *pdev = to_platform_device(dev);
> +	int irq;
> +	u32 ctrl;
> +
> +	irq = platform_get_irq_byname_optional(pdev, split_msi_names[0]);
> +	if (irq == -ENXIO)
> +		return -ENXIO;

You still need to check for other errors and -EPROBE_DEFER here.

> +
> +	pp->msi_irq[0] = irq;
> +
> +	/* Parse as many IRQs as described in the DTS. */

s/DTS/devicetree/

> +	for (ctrl = 1; ctrl < MAX_MSI_CTRLS; ctrl++) {
> +		irq = platform_get_irq_byname_optional(pdev, split_msi_names[ctrl]);
> +		if (irq == -ENXIO)
> +			break;
> +		if (irq < 0)
> +			return dev_err_probe(dev, irq,
> +					     "Failed to parse MSI IRQ '%s'\n",
> +					     split_msi_names[ctrl]);
> +
> +		pp->msi_irq[ctrl] = irq;
> +	}
> +
> +	pp->num_vectors = ctrl * MAX_MSI_IRQS_PER_CTRL;
> +
> +	return 0;
> +}
> +
>  static int dw_pcie_msi_host_init(struct pcie_port *pp)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> @@ -295,22 +332,34 @@ static int dw_pcie_msi_host_init(struct pcie_port *pp)
>  	struct platform_device *pdev = to_platform_device(dev);
>  	int ret;
>  	u32 ctrl, num_ctrls;
> +	bool has_split_msi_irq = false;

This one should go in the follow-on patch that starts using it.

> -	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
> -	for (ctrl = 0; ctrl < num_ctrls; ctrl++)
> +	for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++)
>  		pp->irq_mask[ctrl] = ~0;
>  
> +	if (!pp->msi_irq[0]) {
> +		ret = dw_pcie_parse_split_msi_irq(pp);
> +		if (ret < 0 && ret != -ENXIO)
> +			return ret;
> +	}
> +
> +	if (!pp->num_vectors)
> +		pp->num_vectors = MSI_DEF_NUM_VECTORS;

This works, but now you override num_vectors unconditionally when using
split msis (and not just when num_vectors is set to zero).

Is it work allowing to use num_vectors as a maximum as in previous
versions (if only for consistency)?

> +	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
> +
>  	if (!pp->msi_irq[0]) {
>  		int irq = platform_get_irq_byname_optional(pdev, "msi");
>  
>  		if (irq < 0) {
>  			irq = platform_get_irq(pdev, 0);
>  			if (irq < 0)
> -				return irq;
> +				return dev_err_probe(dev, irq, "Failed to parse MSI irq\n");
>  		}
>  		pp->msi_irq[0] = irq;
>  	}
>  
> +	dev_dbg(dev, "Using %d MSI vectors\n", pp->num_vectors);
> +
>  	pp->msi_irq_chip = &dw_pci_msi_bottom_irq_chip;
>  
>  	ret = dw_pcie_allocate_domains(pp);
> @@ -407,7 +456,8 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  				     of_property_read_bool(np, "msi-parent") ||
>  				     of_property_read_bool(np, "msi-map"));
>  
> -		if (!pp->num_vectors) {
> +		/* for the has_msi_ctrl the default assignment is handled inside dw_pcie_msi_host_init() */
> +		if (!pp->has_msi_ctrl && !pp->num_vectors) {
>  			pp->num_vectors = MSI_DEF_NUM_VECTORS;
>  		} else if (pp->num_vectors > MAX_MSI_IRQS) {
>  			dev_err(dev, "Invalid number of vectors\n");

Johan