PCI UDD Questions

Jan Kiszka jan.kiszka at siemens.com
Wed Mar 6 18:38:47 CET 2019

On 06.03.19 12:24, Philippe Gerum via Xenomai wrote:
> On 3/2/19 1:25 PM, Jeff Webb via Xenomai wrote:
>> I could also avoid using the PCI command register entirely and just write to a device-specific mask bit in my peripheral, but I would rather implement a generic solution if there is not a performance penalty for using the PCI command register.
> I don't think that using the PCI layer would be cheaper than tweaking
> some bit in your device. The former involves a serialization on
> pci_lock, then a read-update-write sequence to send the
> masking/unmasking command to the bus layer. Sending the acknowledge to
> the device in order to stop it from interrupting is the usual way for rt
> sources.

Plus PCI config accesses (which are needed for generic INTx masking) are 
generally more expensive than device register accesses. So don't use them for 
masking, whenever possible.


Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

More information about the Xenomai mailing list