linux-kernel - Re: [PATCH v18 1/5] iommu/arm-smmu: Add pm

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Message-ID: <20181130181536.GA15274@arm.com>
Date:   Fri, 30 Nov 2018 18:15:37 +0000
From:   Will Deacon <will.deacon@....com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
Cc:     Robin Murphy <robin.murphy@....com>, sboyd@...nel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        Joerg Roedel <joro@...tes.org>, robh+dt <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        open list <linux-kernel@...r.kernel.org>,
        alex.williamson@...hat.com,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>
Subject: Re: [PATCH v18 1/5] iommu/arm-smmu: Add pm_runtime/sleep ops

On Thu, Nov 29, 2018 at 08:25:20PM +0530, Vivek Gautam wrote:
> On Wed, Nov 28, 2018 at 10:07 PM Robin Murphy <robin.murphy@....com> wrote:
> >
> > On 28/11/2018 16:24, Stephen Boyd wrote:
> > > Quoting Vivek Gautam (2018-11-27 02:11:41)
> > >> @@ -1966,6 +1970,23 @@ static const struct of_device_id arm_smmu_of_match[] = {
> > >>   };
> > >>   MODULE_DEVICE_TABLE(of, arm_smmu_of_match);
> > >>
> > >> +static void arm_smmu_fill_clk_data(struct arm_smmu_device *smmu,
> > >> +                                  const char * const *clks)
> > >> +{
> > >> +       int i;
> > >> +
> > >> +       if (smmu->num_clks < 1)
> > >> +               return;
> > >> +
> > >> +       smmu->clks = devm_kcalloc(smmu->dev, smmu->num_clks,
> > >> +                                 sizeof(*smmu->clks), GFP_KERNEL);
> > >> +       if (!smmu->clks)
> > >> +               return;
> > >> +
> > >> +       for (i = 0; i < smmu->num_clks; i++)
> > >> +               smmu->clks[i].id = clks[i];
> > >
> > > Is this clk_bulk_get_all()?
> 
> From what I remember, and now I could go back to v7 and check [1], we parked
> clk_bulk_get out of OF's sole purview as we also have
> arm_smmu_device_acpi_probe() besides arm_smmu_device_dt_probe().
> 
> arm_smmu_device_dt_probe() could get the clocks from dt and fill in
> the clock bulk data, and
> similarly, arm_smmu_device_acpi_probe() could fill the clock bulk data
> by getting it from ACPI.
> 
> clk_bulk_get_all() seems like going only the OF way.
> Is there another way here to have something common between ACPI
> and OF, and then do the clk_bulk_get?

I'd say just go with clk_bulk_get_all() and if somebody really wants to
mess with the SMMU clocks on a system booted via ACPI, then it's their
problem to solve. My understanding is that the design of IORT makes this
next to impossible to solve anyway, because a static table is used and
therefore we're unable to run whatever ASL methods need to be invoked to
mess with the clocks.

Will