linux-kernel - Re: [PATCH v2 04/10] drm/IB/hfi1: Use RMW accessors for changing LNKCTL2

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Date:   Fri, 15 Sep 2023 17:02:31 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Dean Luick <dean.luick@...nelisnetworks.com>
cc:     linux-pci@...r.kernel.org, Bjorn Helgaas <helgaas@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Lukas Wunner <lukas@...ner.de>,
        Alexandru Gagniuc <mr.nuke.me@...il.com>,
        Krishna chaitanya chundru <quic_krichai@...cinc.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Alex Deucher <alexdeucher@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v2 04/10] drm/IB/hfi1: Use RMW accessors for changing
 LNKCTL2

On Fri, 15 Sep 2023, Dean Luick wrote:
> On 9/15/2023 7:01 AM, Ilpo Järvinen wrote:
> > Don't assume that only the driver would be accessing LNKCTL2. In the
> > case of upstream (parent), the driver does not even own the device it's
> > changing the registers for.
> >
> > Use RMW capability accessors which do proper locking to avoid losing
> > concurrent updates to the register value. This change is also useful as
> > a cleanup.
> >
> > Suggested-by: Lukas Wunner <lukas@...ner.de>
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> 
> I believe the subject should begin with "RDMA/hfi1:", the current expectation for all devices in drivers/infiniband.

Thanks, I'll update it. I hadn't realized given the shortlogs of the other 
commits (no idea where I managed to get that "drm" from, but it's also 
gone now).

> > ---
> >  drivers/infiniband/hw/hfi1/pcie.c | 30 ++++++++----------------------
> >  1 file changed, 8 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/infiniband/hw/hfi1/pcie.c b/drivers/infiniband/hw/hfi1/pcie.c
> > index 08732e1ac966..60a177f52eb5 100644
> > --- a/drivers/infiniband/hw/hfi1/pcie.c
> > +++ b/drivers/infiniband/hw/hfi1/pcie.c
> > @@ -1212,14 +1212,11 @@ int do_pcie_gen3_transition(struct hfi1_devdata *dd)
> >                   (u32)lnkctl2);
> >       /* only write to parent if target is not as high as ours */
> >       if ((lnkctl2 & PCI_EXP_LNKCTL2_TLS) < target_vector) {
> > -             lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
> > -             lnkctl2 |= target_vector;
> > -             dd_dev_info(dd, "%s: ..new link control2: 0x%x\n", __func__,
> > -                         (u32)lnkctl2);
> > -             ret = pcie_capability_write_word(parent,
> > -                                              PCI_EXP_LNKCTL2, lnkctl2);
> > +             ret = pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL2,
> > +                                                      PCI_EXP_LNKCTL2_TLS,
> > +                                                      target_vector);
> >               if (ret) {
> > -                     dd_dev_err(dd, "Unable to write to PCI config\n");
> > +                     dd_dev_err(dd, "Unable to change PCI target speed\n");
> 
> To differentiate from the dev_err below, add "parent", i.e. "Unable to change parent PCI target speed".
> 
> 
> >                       return_error = 1;
> >                       goto done;
> >               }
> > @@ -1228,22 +1225,11 @@ int do_pcie_gen3_transition(struct hfi1_devdata *dd)
> >       }
> >
> >       dd_dev_info(dd, "%s: setting target link speed\n", __func__);
> > -     ret = pcie_capability_read_word(dd->pcidev, PCI_EXP_LNKCTL2, &lnkctl2);
> > +     ret = pcie_capability_clear_and_set_word(dd->pcidev, PCI_EXP_LNKCTL2,
> > +                                              PCI_EXP_LNKCTL2_TLS,
> > +                                              target_vector);
> >       if (ret) {
> > -             dd_dev_err(dd, "Unable to read from PCI config\n");
> > -             return_error = 1;
> > -             goto done;
> > -     }
> > -
> > -     dd_dev_info(dd, "%s: ..old link control2: 0x%x\n", __func__,
> > -                 (u32)lnkctl2);
> > -     lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
> > -     lnkctl2 |= target_vector;
> > -     dd_dev_info(dd, "%s: ..new link control2: 0x%x\n", __func__,
> > -                 (u32)lnkctl2);
> > -     ret = pcie_capability_write_word(dd->pcidev, PCI_EXP_LNKCTL2, lnkctl2);
> > -     if (ret) {
> > -             dd_dev_err(dd, "Unable to write to PCI config\n");
> > +             dd_dev_err(dd, "Unable to change PCI target speed\n");
> 
> To differentiate from the dev_err above, add "device", i.e. "Unable to change device PCI target speed".

Okay, I'll change those. Thanks for taking a look.

-- 
 i.