RE: [RFC 2/2] pci-expender-bus:Add pcie-root-port to pxb-pcie under arm.

[miaoyubo]

> -----Original Message-----
> From: Daniel P. Berrangé [mailto:address@hidden]
> Sent: Monday, February 24, 2020 8:36 PM
> To: miaoyubo <address@hidden>
> Cc: address@hidden; address@hidden; address@hidden;
> Xiexiangyou <address@hidden>; address@hidden;
> address@hidden
> Subject: Re: [RFC 2/2] pci-expender-bus:Add pcie-root-port to pxb-pcie
> under arm.
> 
> On Sat, Feb 15, 2020 at 08:59:28AM +0000, miaoyubo wrote:
> >
> > > -----Original Message-----
> > > From: Daniel P. Berrangé [mailto:address@hidden]
> > > Sent: Friday, February 14, 2020 6:25 PM
> > > To: miaoyubo <address@hidden>
> > > Cc: address@hidden; address@hidden;
> > > address@hidden; address@hidden; Xiexiangyou
> > > <address@hidden>; address@hidden
> > > Subject: Re: [RFC 2/2] pci-expender-bus:Add pcie-root-port to
> > > pxb-pcie under arm.
> > >
> > > On Fri, Feb 14, 2020 at 07:25:43AM +0000, miaoyubo wrote:
> > > >
> > > > > -----Original Message-----
> > > > > From: Daniel P. Berrangé [mailto:address@hidden]
> > > > > Sent: Thursday, February 13, 2020 9:52 PM
> > > > > To: miaoyubo <address@hidden>
> > > > > Cc: address@hidden; address@hidden;
> > > > > address@hidden; address@hidden; Xiexiangyou
> > > > > <address@hidden>; address@hidden
> > > > > Subject: Re: [RFC 2/2] pci-expender-bus:Add pcie-root-port to
> > > > > pxb-pcie under arm.
> > > > >
> > > > > On Thu, Feb 13, 2020 at 03:49:52PM +0800, Yubo Miao wrote:
> > > > > > From: miaoyubo <address@hidden>
> > > > > >
> > > > > > Since devices could not directly plugged into pxb-pcie, under
> > > > > > arm, one pcie-root port is plugged into pxb-pcie. Due to the
> > > > > > bus for each pxb-pcie is defined as 2 in acpi dsdt tables(one
> > > > > > for pxb-pcie, one for pcie-root-port), only one device could
> > > > > > be plugged into
> > > one pxb-pcie.
> > > > >
> > > > > What is the cause of this arm specific requirement for pxb-pcie
> > > > > and more importantly can be fix it so that we don't need this patch ?
> > > > > I think it is highly undesirable to have such a per-arch
> > > > > difference in configuration of the pxb-pcie device. It means any
> > > > > mgmt app which already supports pxb-pcie will be broken and need
> to special case arm.
> > > > >
> > > >
> > > > Thanks for your reply, Without this patch, the pxb-pcie is also
> > > > useable, however, one extra pcie-root-port or pci-bridge or
> > > > something else need to be defined by mgmt. app. This patch will could
> be abandoned.
> > >
> > > That's not really answering my question. IIUC, this pxb-pcie device
> > > works fine on x86_64, and I want to know why it doesn't work on arm ?
> > > Requiring different setups by the mgmt apps is not at all nice
> > > because it will inevitably lead to broken arm setups. x86_64 gets
> > > far more testing & usage, developers won't realize arm is different.
> > >
> > >
> >
> > Thanks for replying. Currently, on x86_64, pxb-pcie devices is
> > presented in acpi tables but on arm, It is not, only one main host
> > bridge is presented for arm in acpi dsdt tables. That's why pxb-pcie
> > works on
> > x86_64 but doesn't work on arm. The patch 1/2 do the work to present
> > and allocate resources for pxb-pcie in arm.
> 
> Yes, this first patch makes sense
> 

Thanks for the comments, the patch has been updated to v4, pls check it.

> > For x86_64, if one device is going to be plugged into pxb-pcie, one
> > extra pcie-root-port or pci-bridge have to be defined and plugged on
> > pxb-pcie, then the device is plugged on the pcie-root-port or pci-bridge.
> 
> > This patch 2/2 just auto defined one pcie-root-port for arm. If this
> > patch abandoned, the usage of pxb-pcie would be the same with x86_64,
> > therefore, to keep the same step for x86 and arm, this patch 2/2 could
> > be abandonded.
> 
> Yes, I think abandoning this patch 2 is best. Applications that know how to
> use pxb-pcie on x86_64, will already do the right thing on arm too, once your
> first patch is merged.
> 

This patch has been abandoned since v3.

> Regards,
> Daniel
> --
> |: https://berrange.com      -o-
> https://www.flickr.com/photos/dberrange :|
> |: https://libvirt.org         -o-            https://fstop138.berrange.com :|
> |: https://entangle-photo.org    -o-
> https://www.instagram.com/dberrange :|


Regards,
Miao