Re: [PATCH v12 04/16] baseband/acc: introduce PMD for ACC200

[Thomas Monjalon <thomas@monjalon.net>]

31/10/2022 16:43, Chautru, Nicolas:
> From: Thomas Monjalon <thomas@monjalon.net>
> > 12/10/2022 19:59, Nicolas Chautru:
> > > +Bind PF UIO driver(s)
> > > +~~~~~~~~~~~~~~~~~~~~~
> > > +
> > > +Install the DPDK igb_uio driver, bind it with the PF PCI device ID
> > > +and use ``lspci`` to confirm the PF device is under use by ``igb_uio`` DPDK
> > UIO driver.
> > 
> > igb_uio is not recommended.
> > Please focus on VFIO first.
> > 
> > > +The igb_uio driver may be bound to the PF PCI device using one of two
> > > +methods for ACC200:
> > > +
> > > +
> > > +1. PCI functions (physical or virtual, depending on the use case) can
> > > +be bound to the UIO driver by repeating this command for every function.
> > > +
> > > +.. code-block:: console
> > > +
> > > +  cd <dpdk-top-level-directory>
> > > +  insmod ./build/kmod/igb_uio.ko
> > > +  echo "8086 57c0" > /sys/bus/pci/drivers/igb_uio/new_id
> > > +  lspci -vd8086:57c0
> > > +
> > > +
> > > +2. Another way to bind PF with DPDK UIO driver is by using the
> > > +``dpdk-devbind.py`` tool
> > > +
> > > +.. code-block:: console
> > > +
> > > +  cd <dpdk-top-level-directory>
> > > +  ./usertools/dpdk-devbind.py -b igb_uio 0000:f7:00.0
> > > +
> > > +where the PCI device ID (example: 0000:f7:00.0) is obtained using
> > > +lspci -vd8086:57c0
> > 
> > This binding is not specific to the driver.
> > It would be better to refer to the Linux guide instead of duplicating it again
> > and again.
> > 
> > > +In a similar way the PF may be bound with vfio-pci as any PCIe device.
> > 
> > You could mention igb_uio here.
> > Is there any advantage in using igb_uio?
> > 
> 
> Igb_uio is arguably easier to use to new user tend to start with it or specific ecosystem. This is typically the entry point (no iommu, no flr below the bonnet, no vfio token...) hence good to have a bit of handholding with a couple of lines capturing how to easily run a few tests. I don't believe this is too redundant to have these few lines compared to the help in bring to the user not having to double guess their steps. 
> More generally there are a number of module drivers combinations that are supported based on different deployments. We don't document in too much details for the details since that is not too ACC specific and there is more documentation no pf_bb_config repo for using the PMD from the VF.. 
> 
> Basically Thomas let us know more explicitly what you are suggesting as documentation update. You just want more emphasis on vfio-pci flow (which is fair, some of it documented on pf_bb_config including the vfio token passing but we can reproduce here as well) or something else? 

There are 2 things to change:
1/ igb_uio is going to be deprecated, so we must emphasize on VFIO
2/ for doc maintenance, it is better to have common steps described in one place.
If needed, you can change the common doc and refer to it.