linux-kernel - Re: [PATCH v16 2/5] iommu/arm-smmu: Invoke pm

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Date:   Fri, 7 Sep 2018 18:16:37 +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>,
        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>,
        devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rob Clark <robdclark@...il.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>, sboyd@...nel.org,
        jcrouse@...eaurora.org, Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v16 2/5] iommu/arm-smmu: Invoke pm_runtime during probe,
 add/remove device

Hi Vivek,

On Thu, Aug 30, 2018 at 11:46 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.
> Global locks are also initialized before enabling runtime pm as the
> runtime_resume() calls device_reset() which does tlb_sync_global()
> that ultimately requires locks to be initialized.
>
> 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>
> ---
>  drivers/iommu/arm-smmu.c | 89 +++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 81 insertions(+), 8 deletions(-)
[snip]
> @@ -2215,10 +2281,17 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
>         if (!bitmap_empty(smmu->context_map, ARM_SMMU_MAX_CBS))
>                 dev_err(&pdev->dev, "removing device with active domains!\n");
>
> +       arm_smmu_rpm_get(smmu);
>         /* Turn the thing off */
>         writel(sCR0_CLIENTPD, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
> +       arm_smmu_rpm_put(smmu);
> +
> +       if (pm_runtime_enabled(smmu->dev))
> +               pm_runtime_force_suspend(smmu->dev);
> +       else
> +               clk_bulk_disable(smmu->num_clks, smmu->clks);
>
> -       clk_bulk_disable_unprepare(smmu->num_clks, smmu->clks);
> +       clk_bulk_unprepare(smmu->num_clks, smmu->clks);

Aren't we missing pm_runtime_disable() here? We'll have the enable
count unbalanced if the driver is removed and probed again.

Also, if we add pm_runtime_disable(), we can reorder things a bit and
simplify into:

       arm_smmu_rpm_get(smmu);

       /* Turn the thing off */
       writel(sCR0_CLIENTPD, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);

       if (pm_runtime_enabled())
               pm_runtime_disable();
        arm_smmu_rpm_put(smmu);

        clk_bulk_disable_unprepare(smmu->num_clks, smmu->clks);

Best regards,
Tomasz