linux-kernel - Re: [PATCH v7 2/6] iommu/arm-smmu: Add pm

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Date:   Tue, 13 Feb 2018 17:03:48 +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 2/6] iommu/arm-smmu: Add pm_runtime/sleep ops

Hi Vivek,

Thanks for the patch. Please see some comments inline.

On Wed, Feb 7, 2018 at 7:31 PM, Vivek Gautam
<vivek.gautam@...eaurora.org> wrote:
> From: Sricharan R <sricharan@...eaurora.org>
>
> The smmu needs to be functional only when the respective
> master's using it are active. The device_link feature
> helps to track such functional dependencies, so that the
> iommu gets powered when the master device enables itself
> using pm_runtime. So by adapting the smmu driver for
> runtime pm, above said dependency can be addressed.
>
> This patch adds the pm runtime/sleep callbacks to the
> driver and also the functions to parse the smmu clocks
> from DT and enable them in resume/suspend.
>
> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> Signed-off-by: Archit Taneja <architt@...eaurora.org>
> [vivek: Clock rework to request bulk of clocks]
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> ---
>  drivers/iommu/arm-smmu.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 54 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 69e7c60792a8..9e2f917e16c2 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -48,6 +48,7 @@
>  #include <linux/of_iommu.h>
>  #include <linux/pci.h>
>  #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/slab.h>
>  #include <linux/spinlock.h>
>
> @@ -205,6 +206,8 @@ struct arm_smmu_device {
>         u32                             num_global_irqs;
>         u32                             num_context_irqs;
>         unsigned int                    *irqs;
> +       struct clk_bulk_data            *clocks;
> +       int                             num_clks;

nit: Perhaps "num_clocks" to be consistent with "clocks"?

>
>         u32                             cavium_id_base; /* Specific to Cavium */
>
> @@ -1897,10 +1900,12 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
>  struct arm_smmu_match_data {
>         enum arm_smmu_arch_version version;
>         enum arm_smmu_implementation model;
> +       const char * const *clks;
> +       int num_clks;

nit: Perhaps s/clks/clocks/ here or s/clocks/clks/ in struct arm_smmu_device?

>  };
>
>  #define ARM_SMMU_MATCH_DATA(name, ver, imp)    \
> -static struct arm_smmu_match_data name = { .version = ver, .model = imp }
> +static const struct arm_smmu_match_data name = { .version = ver, .model = imp }
>
>  ARM_SMMU_MATCH_DATA(smmu_generic_v1, ARM_SMMU_V1, GENERIC_SMMU);
>  ARM_SMMU_MATCH_DATA(smmu_generic_v2, ARM_SMMU_V2, GENERIC_SMMU);
> @@ -2001,6 +2006,7 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev,
>         data = of_device_get_match_data(dev);
>         smmu->version = data->version;
>         smmu->model = data->model;
> +       smmu->num_clks = data->num_clks;
>
>         parse_driver_options(smmu);
>
> @@ -2039,6 +2045,28 @@ static void arm_smmu_bus_init(void)
>  #endif
>  }
>
> +static int arm_smmu_init_clks(struct arm_smmu_device *smmu)
> +{
> +       int i;
> +       int num = smmu->num_clks;
> +       const struct arm_smmu_match_data *data;
> +
> +       if (num < 1)
> +               return 0;
> +
> +       smmu->clocks = devm_kcalloc(smmu->dev, num,
> +                                   sizeof(*smmu->clocks), GFP_KERNEL);
> +       if (!smmu->clocks)
> +               return -ENOMEM;
> +
> +       data = of_device_get_match_data(smmu->dev);
> +
> +       for (i = 0; i < num; i++)
> +               smmu->clocks[i].id = data->clks[i];

I'd argue that arm_smmu_device_dt_probe() is a better place for all
the code above, since this function is called regardless of whether
the device is probed from DT or not. Going further,
arm_smmu_device_acpi_probe() could fill smmu->num_clks and ->clocks
using ACPI-like way (as opposed to OF match data) if necessary.

Best regards,
Tomasz