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

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Message-ID: <c0e07dbf-e19e-43b7-9c95-8025a12323b8@cornelisnetworks.com>
Date:   Fri, 15 Sep 2023 08:51:01 -0500
From:   Dean Luick <dean.luick@...nelisnetworks.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        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,
        linux-kernel@...r.kernel.org
Cc:     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 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.

> ---
>  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".



>               return_error = 1;
>               goto done;
>       }

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