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Date: Tue, 13 Feb 2018 17:31:57 +0900 From: Tomasz Figa <tfiga@...omium.org> To: Vivek Gautam <vivek.gautam@...eaurora.org> Cc: "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg Roedel <joro@...tes.org>," <joro@...tes.org>, Rob Herring <robh+dt@...nel.org>, Mark Rutland <mark.rutland@....com>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Robin Murphy <robin.murphy@....com>, Will Deacon <will.deacon@....com>, Rob Clark <robdclark@...il.com>, "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, dri-devel <dri-devel@...ts.freedesktop.org>, freedreno@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>, Greg KH <gregkh@...uxfoundation.org>, sboyd@...eaurora.org, linux-arm-msm@...r.kernel.org Subject: Re: [PATCH v7 4/6] iommu/arm-smmu: Add the device_link between masters and smmu Hi Vivek, Thanks for the patch. Please see my comments inline. On Wed, Feb 7, 2018 at 7:31 PM, Vivek Gautam <vivek.gautam@...eaurora.org> wrote: > From: Sricharan R <sricharan@...eaurora.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@...eaurora.org> > Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org> > --- > drivers/iommu/arm-smmu.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > index c024f69c1682..c7e924d553bd 100644 > --- a/drivers/iommu/arm-smmu.c > +++ b/drivers/iommu/arm-smmu.c > @@ -215,6 +215,9 @@ struct arm_smmu_device { > > /* IOMMU core code handle */ > struct iommu_device iommu; > + > + /* runtime PM link to master */ > + struct device_link *link; > }; > > enum arm_smmu_context_fmt { > @@ -1425,6 +1428,17 @@ static int arm_smmu_add_device(struct device *dev) > > pm_runtime_put_sync(smmu->dev); > > + /* > + * Establish the link between smmu and master, so that the > + * smmu gets runtime enabled/disabled as per the master's > + * needs. > + */ > + smmu->link = device_link_add(dev, smmu->dev, DL_FLAG_PM_RUNTIME); > + if (!smmu->link) > + dev_warn(smmu->dev, > + "Unable to create device link between %s and %s\n", > + dev_name(smmu->dev), dev_name(dev)); How likely it is that the master can work normally even if the link add fails? Perhaps we should just return an error here? > + > return 0; > > out_rpm_put: > @@ -1449,6 +1463,8 @@ static void arm_smmu_remove_device(struct device *dev) > cfg = fwspec->iommu_priv; > smmu = cfg->smmu; > > + device_link_del(smmu->link); We allowed smmu->link in arm_smmu_add_device(), but here we don't check it. Looking at the code, device_link_del() doesn't seem to check either. Note that this problem would go away if we fail add_device on device_link_add() failure, as I suggested above, so no change would be necessary. Best regards, Tomasz
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