[mythtv-users] DVB tuner not working in Xen PV guest

[Christian]

2011/7/24 Simon Hobson <linux at thehobsons.co.uk>

> I'm trying get a new version of MythTV running as a Xen PV guest.
> Host is Debian with Xen4.0.1 and kernel 2.6.32-5-xen-amd64, PV guest
> is also Debian with kernel 2.6.32-5-xen-amd64. I have a DVB-T tuner
> (HVR-1200, PCIe card) I am trying to use in the guest with
> pciback.hide etc. The whole thing is running on an HP Proliant
> Microserver I bought while HP had a mail-in rebate going.
>
> I've had a similar setup with an HVR 1100 under earlier versions of
> Xen, Linux, and MythTV for some time.
>
>
> If I boot the host without Xen, I can access the card with dvbtune
> and it lists the channels in a multiplex :
> ># dvbtune -f 801833000 -i
> >Using DVB card "NXP TDA10048HN DVB-T"
> >tuning DVB-T (in United Kingdom) to 801833000 Hz
> >polling....
> >Getting frontend event
> >FE_STATUS:
> >polling....
> >Getting frontend event
> >FE_STATUS: FE_HAS_SIGNAL FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI
> FE_HAS_SYNC
> >Bit error rate: 35
> >Signal strength: 65278
> >SNR: 246
> >FE_STATUS: FE_HAS_SIGNAL FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI
> FE_HAS_SYNC
> ><transponder type="T" freq="801833000">
> ><service id="4168" ca="0">
> ><description tag="0x48" type="1" provider_name="BBC" service_name="BBC
> ONE" />
> ><descriptor tag="0x73" data="66702e6262632e636f2e756b" text="fp.bbc.co.uk"
> />
> ><stream type="2" pid="101">
> ><stream_id id="1" />
> ></stream>
>
> And the card shows up in the boot log :
> >02:00.0 Multimedia video controller: Conexant Systems, Inc. CX23885
> >PCI Video and Audio Decoder (rev 02)
>
> I've hidden the card from Dom0 by adding "xen-pciback.hide=(02:00.0)"
> to the grub config.
>
>
> When I boot the guest, I can see it's tuner card
> >eddi kernel: [   25.348011] cx23885[0]/0: found at 0000:00:00.0,
> >rev: 2, irq: 16, latency: 0, mmio: 0xfe600000
>
> But if I try to access it with dvbtune, it can't detect any channels :
>
> ># dvbtune -f 801833000 -i
> >Using DVB card "NXP TDA10048HN DVB-T"
> >tuning DVB-T (in United Kingdom) to 801833000 Hz
> >polling....
> >Getting frontend event
> >FE_STATUS:
> >polling....
> >Getting frontend event
> >FE_STATUS: FE_HAS_SIGNAL FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI
> FE_HAS_SYNC
> >Bit error rate: 1965
> >Signal strength: 61680
> >SNR: 131
> >FE_STATUS: FE_HAS_SIGNAL FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI
> FE_HAS_SYNC
> ><transponder type="T" freq="801833000">
> >Nothing to read from fd_pat
> >Nothing to read from fd_sdt
> ></transponder>
>
> Now, that looks very much to me like it recognises there is a signal
> (HAS_SIGNAL, HAS_LOCK, and so on), but it cannot read any data.
>
> Does anyone have any suggestions what may be missing here ?
> Is the "mmio: 0xfe600000" significant, or does that get handled
> automatically with the pciback stuff ?
> --
> Simon Hobson
>
> Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
> author Gladys Hobson. Novels - poetry - short stories - ideal as
> Christmas stocking fillers. Some available as e-books.
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The PCI Passthrough guide at
http://wiki.xensource.com/xenwiki/XenPCIpassthrough states that
swiotlb=force and iommu=soft must be set as kernel boot options in the
domU.  Have you already tried hat?
Let me know if it works, I'm also interested in virtualizing my backend.
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