linux-kernel - Re: [Patch v15 2/5] iommu/arm-smmu: Invoke pm

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Date:   Thu, 30 Aug 2018 14:52:01 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Joerg Roedel <joro@...tes.org>, "robh+dt" <robh+dt@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Linux PM <linux-pm@...r.kernel.org>, sboyd@...nel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        alex.williamson@...hat.com,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Andy Gross <andy.gross@...aro.org>
Subject: Re: [Patch v15 2/5] iommu/arm-smmu: Invoke pm_runtime during probe,
 add/remove device

On Mon, Aug 27, 2018 at 4:27 PM Vivek Gautam
<vivek.gautam@...eaurora.org> wrote:
>
> From: Sricharan R <sricharan@...eaurora.org>
>
> The smmu device probe/remove and add/remove master device callbacks
> gets called when the smmu is not linked to its master, that is without
> the context of the master device. So calling runtime apis in those places
> separately.
>
> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> [vivek: Cleanup pm runtime calls]
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> Reviewed-by: Tomasz Figa <tfiga@...omium.org>
> Tested-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>
> Changes since v14:
>  - none.
>
>  drivers/iommu/arm-smmu.c | 101 +++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 93 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index a81224bc6637..23b4a60149b6 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c

[snip]

> @@ -2131,6 +2188,26 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>         if (err)
>                 return err;
>
> +       /*
> +        * We want to avoid touching dev->power.lock in fastpaths unless
> +        * it's really going to do something useful - pm_runtime_enabled()
> +        * can serve as an ideal proxy for that decision. So, conditionally
> +        * enable pm_runtime.
> +        */
> +       if (dev->pm_domain)
> +               pm_runtime_enable(dev);
> +
> +       err = arm_smmu_rpm_get(smmu);

We shouldn't be doing a runtime_get() yet, as this eventually calls
arm_smmu_device_reset().
arm_smmu_device_reset() should be called only after arm_smmu_device_cfg_probe().
So, I plan to replace the pm_runtime_get/put() calls in probe() with
simple clk_bulk_enable()
to let the driver initialize smmu, and at the end of the probe we can
disable the clocks and
enable runtime pm over the device to let it take care of the device further-on.

> +       if (err < 0)
> +               return err;
> +
> +       /* Enable clocks explicitly if runtime PM is disabled */
> +       if (!pm_runtime_enabled(dev)) {
> +               err = clk_bulk_enable(smmu->num_clks, smmu->clks);
> +               if (err)
> +                       return err;
> +       }
> +
>         err = arm_smmu_device_cfg_probe(smmu);
>         if (err)
>                 return err;

[snip]

Best regards
Vivek
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