Re: [dpdk-dev] [PATCH v3 2/4] net/mrvl: add mrvl net pmd driver

[Tomasz Duszynski <tdu@semihalf.com>]

On Thu, Oct 05, 2017 at 06:29:12PM +0100, Ferruh Yigit wrote:
> On 10/5/2017 9:43 AM, Tomasz Duszynski wrote:
> > On Wed, Oct 04, 2017 at 05:59:11PM +0100, Ferruh Yigit wrote:
> >> On 10/4/2017 9:59 AM, Tomasz Duszynski wrote:
> >>> On Wed, Oct 04, 2017 at 01:24:27AM +0100, Ferruh Yigit wrote:
> >>>> On 10/3/2017 12:51 PM, Tomasz Duszynski wrote:
> >>>>> Add support for the Marvell PPv2 (Packet Processor v2) 1/10 Gbps adapter.
> >>>>> Driver is based on external, publicly available, light-weight Marvell
> >>>>> MUSDK library that provides access to network packet processor.
> >>>>>
> >>>>> Driver comes with support for the following features:
> >>>>>
> >>>>> * Speed capabilities
> >>>>> * Link status
> >>>>> * Queue start/stop
> >>>>> * MTU update
> >>>>> * Jumbo frame
> >>>>> * Promiscuous mode
> >>>>> * Allmulticast mode
> >>>>> * Unicast MAC filter
> >>>>> * Multicast MAC filter
> >>>>> * RSS hash
> >>>>> * VLAN filter
> >>>>> * CRC offload
> >>>>> * L3 checksum offload
> >>>>> * L4 checksum offload
> >>>>> * Packet type parsing
> >>>>> * Basic stats
> >>>>> * Stats per queue
> >>>>
> >>>> I have more detailed comments but in high level,
> >>>> what do you think splitting this patch into three patches:
> >>>> - Skeleton
> >>>> - Add Rx/Tx support
> >>>> - Add features, like MTU update or Promiscuous etc.. support
> >>> If it's how submission process works then I think you left me with no
> >>> other option than splitting driver into nice patchset :).
> >>
> >> No, there is no defined submission process.
> >>
> >>> On the other
> >>> hand driver is really a wrapper to MUSDK library and thus quite easy to
> >>> follow. What are the benefits of such 3-way split?
> >>
> >> To help others review/understand your code. Big code chunks are scary
> >> and I believe most of details gets lost in big code chunks.
> >>
> >> When someone from community wants to understand and update/improve/fix
> >> your code, to help them by logically split the code that their focus can
> >> go into more narrow part.
> >>
> >> But this also means some effort in your side, so some kind of balance is
> >> required.
> >>
> >> I think splitting patch into smaller logical part is helpful for others,
> >> what do you think, is it too much effort?
> >>
> >
> > Fair enough. I'll split the driver as suggested. A few specific
> > questions about functionality each patch should contain though.
> >
> > As for skeleton, I see others just put driver probing here.
> >
> > As for Rx/Tx support it seems that there's no common pattern.
> > Functionality like starting/stopping device, queues configuration
> > and all the other things related to Rx/Tx should be here as well?
>
> As you said there is no common pattern, but I think starting/stopping
> device, queues configuration can go into skeleton and mainly Rx/Tx burst
> functions can go into Rx/Tx patch.
> But please what you think more reasonable matters here.
>

ACK

> >
> > What's left are features which go into features-patch.
>
> Yes.
> And the .ini file, currently part of doc patch, can be part of this
> features patch, it is helps more to see the code add feature and doc
> documents it in same patch.
>

ACK

> >
> >>>>
> >>>>>
> >>>>> Driver was engineered cooperatively by Semihalf and Marvell teams.
> >>>>>
> >>>>> Semihalf:
> >>>>> Jacek Siuda <jck@semihalf.com>
> >>>>> Tomasz Duszynski <tdu@semihalf.com>
> >>>>>
> >>>>> Marvell:
> >>>>> Dmitri Epshtein <dima@marvell.com>
> >>>>> Natalie Samsonov <nsamsono@marvell.com>
> >>>>>
> >>>>> Signed-off-by: Jacek Siuda <jck@semihalf.com>
> >>>>> Signed-off-by: Tomasz Duszynski <tdu@semihalf.com>
> >>>>
> >>>> <...>
> >>>>
> >>>>> +static struct rte_vdev_driver pmd_mrvl_drv = {
> >>>>> +	.probe = rte_pmd_mrvl_probe,
> >>>>> +	.remove = rte_pmd_mrvl_remove,
> >>>>> +};
> >>>>> +
> >>>>> +RTE_PMD_REGISTER_VDEV(net_mrvl, pmd_mrvl_drv);
> >>>>
> >>>> Please help me understand.
> >>>>
> >>>> This driver implemented as virtual driver, because:
> >>>> With the help of custom kernel modules, musdk library already provides
> >>>> userspace datapath support. This PMD is an interface to musdk library.
> >>>> Is this correct?
> >>> That is right. Another reason this NIC is not PCI device.
> >>
> >> We support more bus now :). Out of curiosity, which bus is device on?
> >
> > Bus is called Aurora2. That's proprietary SoC interconnect fabric.
> >
> >>
> >>>>
> >>>> If so, just thinking loud:
> >>>> - Why not implement this PMD directly on top of kernel interface,
> >>>> removing musdk layer completely?
> >>>> - How big problem that this PMD depends on custom kernel code?
> >>> I think the main reason is that MUSDK is already used in different projects.
> >>> Keeping multiple codebases offering similar functionality would be quite
> >>> demanding in terms of extra work needed.
> >>>> - How library and custom kernel code delivered? For which platforms?
> >>> Kernel and library sources are hosted on publicly available repository.
> >>
> >> I guess it would be nice to highlight custom kernel with external
> >> patches is required. This is not mentioned in "Prerequisites" section of
> >> the document.
> >>
> >
> > ACK
> >
> >>> Driver was tested on Armada 7k/8k SoCs.
> >>
> >> Can you please provide link to the HW mentioned in documentation?
> >>
> >
> > You can find some info here:
> >
> > https://www.marvell.com/embedded-processors/armada-70xx/
> > https://www.marvell.com/embedded-processors/armada-80xx/
>
> Thanks, would you mind putting these links into driver documentation as
> well?

ACK

>
> >
> >>>>
> >>>> <....>
> >>>>
> >>>
> >>> --
> >>> - Tomasz Duszyński
> >>>
> >>
> >
> > --
> > - Tomasz Duszyński
> >
>

--
- Tomasz Duszyński