Re: [PATCH net-next v3 0/3] net: stmmac: Add PCI driver support for BCM8958x

[Jitendra Vegiraju <jitendra.vegiraju@broadcom.com>]

On Fri, Aug 2, 2024 at 3:02 AM Serge Semin <fancer.lancer@gmail.com> wrote:
>
> Hi Jitendra
>
> On Thu, Aug 01, 2024 at 08:18:19PM -0700, jitendra.vegiraju@broadcom.com wrote:
> > From: Jitendra Vegiraju <jitendra.vegiraju@broadcom.com>
> >
> > This patchset adds basic PCI ethernet device driver support for Broadcom
> > BCM8958x Automotive Ethernet switch SoC devices.
> >
> > This SoC device has PCIe ethernet MAC attached to an integrated ethernet
> > switch using XGMII interface. The PCIe ethernet controller is presented to
> > the Linux host as PCI network device.
> >
> > The following block diagram gives an overview of the application.
> >              +=================================+
> >              |       Host CPU/Linux            |
> >              +=================================+
> >                         || PCIe
> >                         ||
> >         +==========================================+
> >         |           +--------------+               |
> >         |           | PCIE Endpoint|               |
> >         |           | Ethernet     |               |
> >         |           | Controller   |               |
> >         |           |   DMA        |               |
> >         |           +--------------+               |
> >         |           |   MAC        |   BCM8958X    |
> >         |           +--------------+   SoC         |
> >         |               || XGMII                   |
> >         |               ||                         |
> >         |           +--------------+               |
> >         |           | Ethernet     |               |
> >         |           | switch       |               |
> >         |           +--------------+               |
> >         |             || || || ||                  |
> >         +==========================================+
> >                       || || || || More external interfaces
> >
> > The MAC block on BCM8958x is based on Synopsis XGMAC 4.00a core. This
> > driver uses common dwxgmac2 code where applicable.
>
> Thanks for submitting the series.
>
> I am curious how come Broadcom got to use an IP-core which hasn't
> been even announced by Synopsys. AFAICS the most modern DW XGMAC
> IP-core is of v3.xxa version:
>
> https://www.synopsys.com/dw/ipdir.php?ds=dwc_ether_xgmac
>
I am not sure why the 4.00a IP-code is not announced for general
availability yet.
The Synopsis documentation for this IP mentions 3.xx IP as reference
for this design and lists
new features for 4.00a.

> Are you sure that your device isn't equipped with some another DW MAC
> IP-core, like DW 25G Ethernet MAC? (which BTW is equipped with a new
> Hyper DMA engine with a capability to have up to 128/256 channels with
> likely indirect addressing.) Do I miss something?
>
Yes, I briefly mentioned the new DMA architecture in the commit log
for patch 1/3.
You are correct, the name for the new DMA engine is Hyper DMA. It
probably started with some 3.xx IP-Core.
This DW-MAC is capable of 25G, but this SOC is not using 25G support.

> * I'll join the patch set review after the weekend, sometime on the
> next week.
>
> -Serge(y)
>
> > Driver functionality specific to this MAC is implemented in dwxgmac4.c.
> > Management of integrated ethernet switch on this SoC is not handled by
> > the PCIe interface.
> > This SoC device has PCIe ethernet MAC directly attached to an integrated
> > ethernet switch using XGMII interface.
> >
> > v2->v3:
> >    Addressed v2 comments from Andrew, Jakub, Russel and Simon.
> >    Based on suggestion by Russel and Andrew, added software node to create
> >    phylink in fixed-link mode.
> >    Moved dwxgmac4 specific functions to new files dwxgmac4.c and dwxgmac4.h
> >    in stmmac core module.
> >    Reorganized the code to use the existing glue logic support for xgmac in
> >    hwif.c and override ops functions for dwxgmac4 specific functions.
> >    The patch is split into three parts.
> >      Patch#1 Adds dma_ops for dwxgmac4 in stmmac core
> >      Patch#2 Hooks in the hardware interface handling for dwxgmac4
> >      Patch#3 Adds PCI driver for BCM8958x device
> >
> > v1->v2:
> >    Minor fixes to address coding style issues.
> >    Sent v2 too soon by mistake, without waiting for review comments.
> >    Received feedback on this version.
> >    https://lore.kernel.org/netdev/20240511015924.41457-1-jitendra.vegiraju@broadcom.com/
> >
> > v1:
> >    https://lore.kernel.org/netdev/20240510000331.154486-1-jitendra.vegiraju@broadcom.com/
> >
> > Jitendra Vegiraju (3):
> >   Add basic dwxgmac4 support to stmmac core
> >   Integrate dwxgmac4 into stmmac hwif handling
> >   Add PCI driver support for BCM8958x
> >
> >  MAINTAINERS                                   |   8 +
> >  drivers/net/ethernet/stmicro/stmmac/Kconfig   |  11 +
> >  drivers/net/ethernet/stmicro/stmmac/Makefile  |   3 +-
> >  drivers/net/ethernet/stmicro/stmmac/common.h  |   4 +
> >  .../net/ethernet/stmicro/stmmac/dwmac-brcm.c  | 517 ++++++++++++++++++
> >  .../ethernet/stmicro/stmmac/dwxgmac2_dma.c    |  31 ++
> >  .../net/ethernet/stmicro/stmmac/dwxgmac4.c    | 142 +++++
> >  .../net/ethernet/stmicro/stmmac/dwxgmac4.h    |  84 +++
> >  drivers/net/ethernet/stmicro/stmmac/hwif.c    |  26 +-
> >  drivers/net/ethernet/stmicro/stmmac/hwif.h    |   1 +
> >  10 files changed, 825 insertions(+), 2 deletions(-)
> >  create mode 100644 drivers/net/ethernet/stmicro/stmmac/dwmac-brcm.c
> >  create mode 100644 drivers/net/ethernet/stmicro/stmmac/dwxgmac4.c
> >  create mode 100644 drivers/net/ethernet/stmicro/stmmac/dwxgmac4.h
> >
> > --
> > 2.34.1
> >
> >