Messages in this thread |  | | Date | Sat, 15 Oct 2016 09:39:24 -0700 | From | okaya@codeauro ... | Subject | Re: Why MSI is limited to 32 interrupts maximum |
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On 2016-10-15 06:30, Bharat Kumar Gogada wrote: >> On Sat, 15 Oct 2016 12:37:55 +0000 >> Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com> wrote: >> >> Hi Bharat, >> >> > Can anyone tell why MSI interrupts are limited to maximum 32 >> > interrupts, even though we have 16bit message data register ? >> >> That's the very definition of the original PCI MSI: Up to 32 >> consecutive interrupts >> per function, and a single doorbell address. >> MSI-X lifts that restriction and offers up to 2048 interrupts that do >> not have to >> be contiguous can target individual doorbells. Assuming your MSI >> controller >> advertises MSI-X support and that your devices do support it as well, >> you'll be >> able to enjoy those. >> > > Thanks Marc, so then only 5 bits of message data register will be > used, so what is the purpose rest of the bits ? >
Data field is used to indicate which interrupt number is used. It does not need to start at 0.
You have 32 consecutive interrupts starting from some arbitrary base.
>> > >> > Regards, >> > Bharat >> > >> > >> > This email and any attachments are intended for the sole use of the >> > named recipient(s) and contain(s) confidential information that may be >> > proprietary, privileged or copyrighted under applicable law. If you >> > are not the intended recipient, do not read, copy, or forward this >> > email message or any attachments. Delete this email message and any >> > attachments immediately. >> > >> >> Please fix your email not to carry such disclaimer (or use a private >> email address >> if you can't work around your company policy). Posting confidential >> information >> on a public mailing list feels a bit silly. >> >> Thanks, >> >> M. >> -- >> Without deviation from the norm, progress is not possible. > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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