Re: [PATCH v10 4/5] iommu/arm-smmu: Add the device_link between masters and smmu

From: Tomasz Figa <tfiga-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
To: Vivek Gautam <vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
Cc: Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	rafael.j.wysocki-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
	Linux Kernel Mailing List
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"open list:IOMMU DRIVERS"
	<iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>,
	Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	linux-arm-msm
	<linux-arm-msm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"list-Y9sIeH5OGRo@public.gmane.org:IOMMU DRIVERS
	<iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>,
	Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>,
	"
	<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH v10 4/5] iommu/arm-smmu: Add the device_link between masters and smmu
Date: Fri, 16 Mar 2018 15:41:29 +0900	[thread overview]
Message-ID: <CAAFQd5AAgCE7avK=bR45Kjd=LhJ-qe+kD1otPWPaXUo7_JR65g@mail.gmail.com> (raw)
In-Reply-To: <20180314081434.30875-5-vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

Hi Vivek,

On Wed, Mar 14, 2018 at 5:14 PM, Vivek Gautam
<vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> wrote:
> From: Sricharan R <sricharan-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
>
> Finally add the device link between the master device and
> smmu, so that the smmu gets runtime enabled/disabled only when the
> master needs it. This is done from add_device callback which gets
> called once when the master is added to the smmu.
>
> Signed-off-by: Sricharan R <sricharan-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> Signed-off-by: Vivek Gautam <vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> Reviewed-by: Tomasz Figa <tfiga-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> ---
>
> Changes since v9:
>  - Using device_link_del_dev() to delete the device link, instead of
>    doing it in two steps - device_link_find() to first find the link, and
>    then calling device_link_del().
>
>  drivers/iommu/arm-smmu.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 56a04ae80bf3..4cf270ffd449 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1460,10 +1460,31 @@ static int arm_smmu_add_device(struct device *dev)
>
>         iommu_device_link(&smmu->iommu, dev);
>
> +       if (pm_runtime_enabled(smmu->dev)) {
> +               struct device_link *link;
> +
> +               /*
> +                * Establish the link between smmu and master, so that the
> +                * smmu gets runtime enabled/disabled as per the master's
> +                * needs.
> +                */
> +               link = device_link_add(dev, smmu->dev, DL_FLAG_PM_RUNTIME);
> +               if (!link) {
> +                       dev_warn(smmu->dev,
> +                                "Unable to add link to the consumer %s\n",
> +                                dev_name(dev));
> +                       ret = -ENODEV;
> +                       goto out_unlink;
> +               }
> +       }

If it's an error, we should use dev_err(). Also, as per Robin's
comment for v9 could we make it as follows?

if (pm_runtime_enabled(smmu->dev) &&
    !device_link_add(dev, smmu->dev, DL_FLAG_PM_RUNTIME)) {
        dev_err(smmu->dev,
                         "Unable to add link to the consumer %s\n",
dev_name(dev));
        ret = -ENODEV;
        goto out_unlink;
}

Best regards,
Tomasz