Re: [PATCH 10/11] PCI: tegra194: Fix Endpoint MSI/MSI-X numbering

[Manikanta Maddireddy <mmaddireddy@nvidia.com>]

On 23/09/26 7:02 pm, Niklas Cassel wrote:
> On Wed, Sep 23, 2026 at 12:52:36PM +0530, Manikanta Maddireddy wrote:
>> pci_epc_raise_irq() passes MSI and MSI-X interrupt numbers in the
>> 1-N range. The Tegra MSI path rejected values above 32 but accepted
>> zero, which makes BIT(irq - 1) shift by a negative amount.
>>
>> The Tegra MSI-X path also wrote that 1-based number to the DWC MSI-X
>> doorbell. The doorbell expects a zero-based vector index, matching the
>> common DesignWare doorbell helper which programs interrupt_num - 1.
>>
>> Reject zero for both MSI and MSI-X, read the MSI-X table size directly
>> from the DWC capability, and write irq - 1 to the MSI-X doorbell.
>>
>> Also advertise MSI-X support in the Tegra Endpoint features so endpoint
>> functions can expose and exercise the Tegra MSI-X path.
>>
>> Fixes: c57247f940e8 ("PCI: tegra: Add support for PCIe endpoint mode in Tegra194")
>> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
>> ---
>>   drivers/pci/controller/dwc/pcie-tegra194.c | 25 ++++++++++++++++++----
>>   1 file changed, 21 insertions(+), 4 deletions(-)
> 
> 
> Subject: PCI: tegra194: Fix Endpoint MSI/MSI-X numbering
> 
> Makes it look like the MSI numbering was wrong. It wasn't.
> 
> Don't get me wrong, I think this change makes sense:
> 
>> @@ -2026,7 +2026,7 @@ static int tegra_pcie_ep_raise_intx_irq(struct tegra_pcie_dw *pcie, u16 irq)
>>   
>>   static int tegra_pcie_ep_raise_msi_irq(struct tegra_pcie_dw *pcie, u16 irq)
>>   {
>> -	if (unlikely(irq > 32))
>> +	if (unlikely(!irq || irq > 32))
>>   		return -EINVAL;
>>   
>>   	appl_writel(pcie, BIT(irq - 1), APPL_MSI_CTRL_1);
> 
> But that change should be in a separate commit IMO, as does not not actually
> fix any existing problem. All EPF drivers follow the pci_epc_raise_irq() kdoc,
> and currently call pci_epc_raise_irq() with a value in (1-N).
> 
> 
> 
> That way the commit message for fixing tegra_pcie_ep_raise_msix_irq() is
> also clearer, as you would not be talking about two separate paths in the
> same commit.
> 
> 
> Kind regards,
> Niklas


I’ll wait a few days for others to review it, then split the patch and 
send an updated version.

- Manikanta


-- 
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