netdev - RE: [PATCH net-next 3/7] qed: Add support for RoCE hw init

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Date:   Tue, 18 Oct 2022 10:10:14 +0000
From:   Michal Kalderon <mkalderon@...vell.com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...vell.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: RE: [PATCH net-next 3/7] qed: Add support for RoCE hw init

> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: Tuesday, October 11, 2022 12:45 AM
> 
> [ping, updated Ariel's address]
> 
> On Fri, Oct 07, 2022 at 10:48:32AM -0500, Bjorn Helgaas wrote:
> > On Sat, Oct 01, 2016 at 09:59:57PM +0300, Yuval Mintz wrote:
> > > From: Ram Amrani <Ram.Amrani@...iumnetworks.com>
> > >
> > > This adds the backbone required for the various HW initalizations
> > > which are necessary for the qedr driver - FW notification, resource
> > > initializations, etc.
> > > ...
> >
> > > diff --git a/drivers/net/ethernet/qlogic/qed/qed_roce.c
> b/drivers/net/ethernet/qlogic/qed/qed_roce.c
> > > ...
> > > +	/* Check atomic operations support in PCI configuration space. */
> > > +	pci_read_config_dword(cdev->pdev,
> > > +			      cdev->pdev->pcie_cap + PCI_EXP_DEVCTL2,
> > > +			      &pci_status_control);
> > > +
> > > +	if (pci_status_control & PCI_EXP_DEVCTL2_LTR_EN)
> > > +		SET_FIELD(dev->dev_caps,
> QED_RDMA_DEV_CAP_ATOMIC_OP, 1);
> >
> > I don't understand this.
> >
> >   1) PCI_EXP_DEVCTL2 is a 16-bit register ("word"), not a 32-bit one
> >   ("dword").
> >
> >   2) QED_RDMA_DEV_CAP_ATOMIC_OP is set here but is not read
> anywhere
> >   in this patch.  Is it used by the qed device itself?
> >
> >   3) PCI_EXP_DEVCTL2_LTR_EN is for Latency Tolerance Reporting and is
> >   not related to atomic ops.  I don't know what
> >   QED_RDMA_DEV_CAP_ATOMIC_OP means, but possibly one of these
> was
> >   intended instead?
> >
> >     - PCI_EXP_DEVCAP2_ATOMIC_COMP32 means the device supports 32-
> bit
> >       AtomicOps as a completer.
> >     - PCI_EXP_DEVCAP2_ATOMIC_COMP64 means the device supports 64-
> bit
> >       AtomicOps as a completer.
> >     - PCI_EXP_DEVCAP2_ATOMIC_COMP128 means the device supports
> 128-bit
> >       AtomicOps as a completer.
> >     - PCI_EXP_DEVCTL2_ATOMIC_REQ means the device is allowed to
> >       initiate AtomicOps.
> >
> > (This code is now in qed_rdma.c)

Thanks for looking into this. 
This seems like redundant code and left-overs for supporting the atomic operation verb.
Atomic support is handled by: qedr_pci_set_atomic and introduced with a proper implementation by commit-SHA 20c3ff6114b0c

This code in qed_rdma.c can safely be removed.
Thanks,
Michal