linux-kernel - Re: [PATCH] PCI: dwc: Warn if the MSI ctrl doesn't have an associated platform IRQ in DT

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Message-ID: <43333e1f-dcc2-4691-9551-3c35ba04bf7b@riscstar.com>
Date: Thu, 30 Oct 2025 12:40:52 -0500
From: Alex Elder <elder@...cstar.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>,
 jingoohan1@...il.com, lpieralisi@...nel.org, kwilczynski@...nel.org
Cc: robh@...nel.org, bhelgaas@...gle.com, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: dwc: Warn if the MSI ctrl doesn't have an associated
 platform IRQ in DT

On 10/30/25 12:13 PM, Manivannan Sadhasivam wrote:
> The internal MSI controller in DWC IPs supports multiple MSI ctrls, each
> capable of receiving 32 MSI vectors per ctrl. And each MSI ctrl requires a
> dedicated MSI platform IRQ in devicetree to function. Otherwise, MSIs won't
> be received from the endpoints.
> 
> Currently, dw_pcie_msi_host_init() only registers the IRQ handler if the
> MSI ctrl has the associated MSI platform IRQ in DT. But it doesn't warn if
> the IRQ is not available. This may cause developers/users to believe that
> the platform supports MSI vectors from all MSI ctrls, but it doesn't.
> 
> This discrepancy can happen due to two reasons:
> 
> 1. Controller driver incorrectly set the dw_pcie_rp::num_vectors field.
> 2. DT missed specifying the MSI IRQs
> 
> To catch these, add a warning so that the above mentioned discrepancies
> could be reported and fixed accordingly.
> 
> Fixes: db388348acff ("PCI: dwc: Convert struct pcie_port.msi_irq to an array")
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>


Reviewed-by: Alex Elder <elder@...cstar.com>
Tested-by: Alex Elder <elder@...cstar.com>


> ---
>   drivers/pci/controller/dwc/pcie-designware-host.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 20c9333bcb1c..f163f5b6ad3d 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -357,6 +357,8 @@ int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
>   		if (pp->msi_irq[ctrl] > 0)
>   			irq_set_chained_handler_and_data(pp->msi_irq[ctrl],
>   						    dw_chained_msi_isr, pp);
> +		else
> +			dev_warn(dev, "MSI ctrl %d doesn't have platform IRQ in DT", ctrl);
>   	}
>   
>   	/*