Re: [PATCH] powerpc/pci: Initialize msi_addr_mask for OF-created PCI devices

[Nilay Shroff <nilay@linux.ibm.com>]

On 2/19/26 11:01 PM, Bjorn Helgaas wrote:
> [+cc sparc folks, PCI enumeration via OF likely broken]
> 
> On Tue, Feb 17, 2026 at 11:15:26PM +0530, Nilay Shroff wrote:
>> Recent changes [1] replaced the use of no_64bit_msi with msi_addr_mask.
>> As a result, msi_addr_mask is now expected to be initialized to
>> DMA_BIT_MASK(64) when a pci_dev is set up. However, this initialization
>> was missed on powerpc due to differences in the device initialization
>> path compared to other architectures. Due to this, now pci device probe
>> method fails on powerpc system.
> 
> s/pci/PCI/ to match below.
Ack
> 
>> On powerpc systems, struct pci_dev instances are created from device
>> tree nodes via of_create_pci_dev(). Because msi_addr_mask was not
>> initialized there, it remained zero. Later, during MSI setup,
>> msi_verify_entries() validates the programmed MSI address against
>> pdev->msi_addr_mask. Since the mask was not set correctly, the
>> validation fails, causing PCI driver probe failures for devices on
>> powerpc systems.
>>
>> Initialize pdev->msi_addr_mask to DMA_BIT_MASK(64) in
>> of_create_pci_dev() so that MSI address validation succeeds and device
>> probe works as expected.
>>
>> [1] https://lore.kernel.org/all/20260129-pci-msi-addr-mask-v4-0-70da998f2750@iscas.ac.cn/
>>
>> Fixes: 386ced19e9a3 ("PCI/MSI: Convert the boolean no_64bit_msi flag to a DMA address mask")
>> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
> 
> Looks like this and a similar sparc fix need to be in v7.0.  Would be
> great if they could make v7.0-rc1 (Sunday), but that's pretty close.
> 
> Thomas, you merged 386ced19e9a3.  I'm happy to merge the powerpc and
> sparc fixes, given acks from you and the powerpc & sparc folks, or
> feel free to take them yourself.
> 
>> ---
>>  arch/powerpc/kernel/pci_of_scan.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/pci_of_scan.c b/arch/powerpc/kernel/pci_of_scan.c
>> index 756043dd06e9..26ec97ce6b40 100644
>> --- a/arch/powerpc/kernel/pci_of_scan.c
>> +++ b/arch/powerpc/kernel/pci_of_scan.c
>> @@ -211,6 +211,12 @@ struct pci_dev *of_create_pci_dev(struct device_node *node,
>>  	dev->current_state = PCI_UNKNOWN;	/* unknown power state */
>>  	dev->error_state = pci_channel_io_normal;
>>  	dev->dma_mask = 0xffffffff;
> 
> It's typical to add a blank line between the code above and the
> comment below, as was done in 386ced19e9a3.

Okay will fix this in v2.
> 
>> +	/*
>> +	 * Assume 64-bit addresses for MSI initially. Will be changed to 32-bit
>> +	 * if MSI (rather than MSI-X) capability does not have
>> +	 * PCI_MSI_FLAGS_64BIT. Can also be overridden by driver.
>> +	 */
>> +	dev->msi_addr_mask = DMA_BIT_MASK(64);
>>  
>>  	/* Early fixups, before probing the BARs */
>>  	pci_fixup_device(pci_fixup_early, dev);
>> -- 
>> 2.52.0
>>

Thanks,
--Nilay