Messages in this thread | | | Date | Tue, 7 Dec 2010 22:55:47 -0600 | Subject | Re: Posted Write onto a PCI end point device using Linux | From | Robert Hancock <> |
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On Tue, Dec 7, 2010 at 9:57 PM, Sanka Piyaratna <cesanka@yahoo.com> wrote: > Hi Robert, > Could you please tell me how I can initiate a posted write towards a PCIe > endpoint with larger than 32 bit payload using Linux? > Thanks and regards,
You can try writeq to get a 64-bit payload, but I don't think it's available on all platforms. In particular with a 32-bit CPU, it may not be possible at all. If you need to send bigger payloads then you need to use DMA.
> > Sanka Piyaratna > > ________________________________ > From: Robert Hancock <hancockrwd@gmail.com> > To: Sanka Piyaratna <cesanka@yahoo.com> > Cc: linux-kernel@vger.kernel.org > Sent: Wed, 8 December, 2010 12:16:54 PM > Subject: Re: Posted Write onto a PCI end point device using Linux > > On 12/07/2010 05:29 AM, Sanka Piyaratna wrote: >> Hi, >> >> >> I am wondering whether it is possible to issue a posted write using the >> host >> computer's root complex towards an PCI express end point. I have done this >> using >> >> DMA in the past. However, if posted writes are possible that would save a >> lot of >> >> time and effort and would be quicker too. > > Writes from the CPU to PCI memory are always posted. However, the posted > write buffer size is usually quite limited and so this probably will > still cause CPU overhead when writing any significant amount of data > this way. > >
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