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SubjectRE: [PATCH] PCI: layerscape: Add the SRIOV support in host side
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Hi Xiaowei,

> -----Original Message-----
> From: linux-arm-kernel <linux-arm-kernel-bounces@lists.infradead.org> On
> Behalf Of Xiaowei Bao
>
> > -----Original Message-----
> > From: Robin Murphy <robin.murphy@arm.com>
> > Sent: 2019年12月3日 23:20
> > To: Marc Zyngier <maz@kernel.org>; Xiaowei Bao <xiaowei.bao@nxp.com>
> > Cc: Roy Zang <roy.zang@nxp.com>; lorenzo.pieralisi@arm.com;
> > devicetree@vger.kernel.org; linux-pci@vger.kernel.org; Z.q. Hou
> > <zhiqiang.hou@nxp.com>; linux-kernel@vger.kernel.org; M.h. Lian
> > <minghuan.lian@nxp.com>; robh+dt@kernel.org;
> > linux-arm-kernel@lists.infradead.org; bhelgaas@google.com;
> > andrew.murray@arm.com; frowand.list@gmail.com; Mingkai Hu
> > <mingkai.hu@nxp.com>
> > Subject: Re: [PATCH] PCI: layerscape: Add the SRIOV support in host side
> >
> > On 03/12/2019 11:51 am, Marc Zyngier wrote:
> > > On 2019-12-03 01:42, Xiaowei Bao wrote:
> > >>> -----Original Message-----
> > >>> From: Marc Zyngier <maz@misterjones.org>
> > >>> Sent: 2019年12月2日 20:48
> > >>> To: Xiaowei Bao <xiaowei.bao@nxp.com>
> > >>> Cc: robh+dt@kernel.org; frowand.list@gmail.com; M.h. Lian
> > >>> <minghuan.lian@nxp.com>; Mingkai Hu <mingkai.hu@nxp.com>; Roy
> > Zang
> > >>> <roy.zang@nxp.com>; lorenzo.pieralisi@arm.com;
> > >>> andrew.murray@arm.com; bhelgaas@google.com;
> > >>> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org;
> > >>> linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> > >>> Z.q. Hou <zhiqiang.hou@nxp.com>
> > >>> Subject: Re: [PATCH] PCI: layerscape: Add the SRIOV support in host
> > >>> side
> > >>>
> > >>> On 2019-12-02 10:45, Xiaowei Bao wrote:
> > >>> > GIC get the map relations of devid and stream id from the msi-map
> > >>> > property of DTS, our platform add this property in u-boot base on
> > >>> > the PCIe device in the bus, but if enable the vf device in kernel,
> > >>> > the vf device msi-map will not set, so the vf device can't work,
> > >>> > this patch purpose is that manage the stream id and device id map
> > >>> > relations dynamically in kernel, and make the new PCIe device work
> in
> > kernel.
> > >>> >
> > >>> > Signed-off-by: Xiaowei Bao <xiaowei.bao@nxp.com>
> > >>> > ---
> > >>> >  drivers/of/irq.c                            |  9 +++
> > >>> >  drivers/pci/controller/dwc/pci-layerscape.c | 94
> > >>> > +++++++++++++++++++++++++++++
> > >>> >  drivers/pci/probe.c                         |  6 ++
> > >>> >  drivers/pci/remove.c                        |  6 ++
> > >>> >  4 files changed, 115 insertions(+)
> > >>> >
> > >>> > diff --git a/drivers/of/irq.c b/drivers/of/irq.c index
> > >>> > a296eaf..791e609 100644
> > >>> > --- a/drivers/of/irq.c
> > >>> > +++ b/drivers/of/irq.c
> > >>> > @@ -576,6 +576,11 @@ void __init of_irq_init(const struct
> > >>> >of_device_id
> > >>> > *matches)
> > >>> >      }
> > >>> >  }
> > >>> >
> > >>> > +u32 __weak ls_pcie_streamid_fix(struct device *dev, u32 rid) {
> > >>> > +    return rid;
> > >>> > +}
> > >>> > +
> > >>> >  static u32 __of_msi_map_rid(struct device *dev, struct
> > >>> >device_node **np,
> > >>> >                  u32 rid_in)
> > >>> >  {
> > >>> > @@ -590,6 +595,10 @@ static u32 __of_msi_map_rid(struct device
> > >>> >*dev, struct device_node **np,
> > >>> >          if (!of_map_rid(parent_dev->of_node, rid_in, "msi-map",
> > >>> >                  "msi-map-mask", np, &rid_out))
> > >>> >              break;
> > >>> > +
> > >>> > +    if (rid_out == rid_in)
> > >>> > +        rid_out = ls_pcie_streamid_fix(parent_dev, rid_in);
> > >>>
> > >>> Over my dead body. Get your firmware to properly program the LUT so
> > >>> that it presents the ITS with a reasonable topology. There is
> > >>> absolutely no way this kind of change makes it into the kernel.
> > >>
> > >> Sorry for this, I know it is not reasonable, but I have no other way,
> > >> as I know, ARM get the mapping of stream ID to request ID from the
> > >> msi-map property of DTS, if add a new device which need the stream ID
> > >> and try to get it from the msi-map of DTS, it will failed and not
> > >> work, yes? So could you give me a better advice to fix this issue, I
> > >> would really appreciate any comments or suggestions, thanks a lot.
> > >
> > > Why can't firmware expose an msi-map/msi-map-mask that has a large
> > > enough range to ensure mapping of VFs? What are the limitations of the
> > > LUT that would prevent this from being configured before the kernel
> > > boots?
>
> Thanks for your comments, yes, this is the root cause, we only have 16
> stream
> IDs for PCIe domain, this is the hardware limitation, if there have enough
> stream
> IDs, we can expose an msi-map/msi-map-mask for all PCIe devices in system,
> unfortunately, the stream IDs is not enough, I think other ARM vendor have
> same
> issue that they don't have enough stream IDs.
>
> Thanks
> Xiaowei
>
> >
> > Furthermore, note that this attempt isn't doing anything for the SMMU
> > Stream IDs, so the moment anyone tries to assign those VFs they're still
> going
> > to go bang anyway. Any firmware-based fixup for ID mappings, config
> space
> > addresses, etc. needs to be SR-IOV-aware and account for all *possible*
> > BDFs.
> >
> > On LS2085 at least, IIRC you can configure a single LUT entry to just
> translate
> > the Bus:Device identifier and pass some or all of the Function bits
> straight
> > through as the LSBs of the Stream ID, so I don't believe the relatively
> limited
> > number of LUT registers should be too much of an issue. For example,
> last
> > time I hacked on that I apparently had it set up statically like this:
> >
> > &pcie3 {
> > /* Squash 8:5:3 BDF down to 2:2:3 */
> > msi-map-mask = <0x031f>;
> > msi-map = <0x000 &its 0x00 0x20>,
> > <0x100 &its 0x20 0x20>,
> > <0x200 &its 0x40 0x20>,
> > <0x300 &its 0x60 0x20>;
> > };
>
> Thanks Robin, this is a effective way, but we only have total 16 stream
> IDs for PCIe domain,
> and only assign 4 stream IDs for each PCIe controller if the board have 4
> PCIe controllers,
> this is the root cause, I submitted this patch to dynamically manage these
> stream IDs,
> so that it looks like each PCIe controller has 16 stream IDs. I can
> dynamically allocate and
> release these stream IDs based on the PCIe devices in the current system.
> If use your method,
> we support up to 4 PCIe devices(2 PFs and 2 VFs), it will not achieve our
> purpose.
>

We allocate the Stream_IDs in a static fashion in u-boot, see [1], so if a user would need a larger range for PCI {s}he could adjust that in there. On most of our Layerscape chips the SMMU is configured to 5 bits for TBU_ID plus 10 bits for StreamID. Out of these 10 controllable bits we can effectively use 7 bits giving us a max range of 127 Stream_IDs.

[1] https://gitlab.denx.de/u-boot/u-boot/blob/master/arch/arm/include/asm/arch-fsl-layerscape/stream_id_lsch3.h

---
Best Regards, Laurentiu
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