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Date:   Sat, 9 May 2020 15:03:55 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc:     Maxime Ripard <mripard@...nel.org>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-media <linux-media@...r.kernel.org>,
        linux-sunxi@...glegroups.com,
        Jernej Škrabec <jernej.skrabec@...il.com>
Subject: Re: [linux-sunxi] [PATCH v2 2/2] media: cedrus: Implement runtime PM

On 5/5/20 7:53 AM, Ezequiel Garcia wrote:
> On Wed, 22 Apr 2020 at 01:00, Samuel Holland <samuel@...lland.org> wrote:
>>
>> This allows the VE clocks and PLL_VE to be disabled most of the time.
>> A runtime PM reference is held while streaming.
>>
>> Originally-by: Jernej Škrabec <jernej.skrabec@...il.com>
> 
> Originally-by is not documented, perhaps just go with Signed-off-by,
> as Jernej suggested.
> 
>> Signed-off-by: Samuel Holland <samuel@...lland.org>
>> ---
>>
>> v2: moved PM reference to cedrus_{start,stop}_streaming, based on an
>>     earlier patch by Jernej Skrabec. Removes the need for autosuspend.
>>     I tested this with running 2x v4l2-request-test in parallel.
>>
>> ---
>>  drivers/staging/media/sunxi/cedrus/cedrus.c   |   7 ++
>>  .../staging/media/sunxi/cedrus/cedrus_hw.c    | 106 ++++++++++++------
>>  .../staging/media/sunxi/cedrus/cedrus_hw.h    |   3 +
>>  .../staging/media/sunxi/cedrus/cedrus_video.c |  33 ++++--
>>  4 files changed, 104 insertions(+), 45 deletions(-)
>>
>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
>> index 05a85517ff60..bc27f9430eeb 100644
>> --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
>> @@ -16,6 +16,7 @@
>>  #include <linux/platform_device.h>
>>  #include <linux/module.h>
>>  #include <linux/of.h>
>> +#include <linux/pm.h>
>>
>>  #include <media/v4l2-device.h>
>>  #include <media/v4l2-ioctl.h>
>> @@ -551,12 +552,18 @@ static const struct of_device_id cedrus_dt_match[] = {
>>  };
>>  MODULE_DEVICE_TABLE(of, cedrus_dt_match);
>>
>> +static const struct dev_pm_ops cedrus_dev_pm_ops = {
>> +       SET_RUNTIME_PM_OPS(cedrus_hw_suspend,
>> +                          cedrus_hw_resume, NULL)
>> +};
>> +
>>  static struct platform_driver cedrus_driver = {
>>         .probe          = cedrus_probe,
>>         .remove         = cedrus_remove,
>>         .driver         = {
>>                 .name           = CEDRUS_NAME,
>>                 .of_match_table = of_match_ptr(cedrus_dt_match),
>> +               .pm             = &cedrus_dev_pm_ops,
>>         },
>>  };
>>  module_platform_driver(cedrus_driver);
>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_hw.c b/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
>> index daf5f244f93b..1744e6fcc999 100644
>> --- a/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
>> @@ -19,6 +19,7 @@
>>  #include <linux/dma-mapping.h>
>>  #include <linux/interrupt.h>
>>  #include <linux/clk.h>
>> +#include <linux/pm_runtime.h>
>>  #include <linux/regmap.h>
>>  #include <linux/reset.h>
>>  #include <linux/soc/sunxi/sunxi_sram.h>
>> @@ -140,6 +141,64 @@ static irqreturn_t cedrus_irq(int irq, void *data)
>>         return IRQ_HANDLED;
>>  }
>>
>> +int cedrus_hw_suspend(struct device *device)
>> +{
>> +       struct cedrus_dev *dev = dev_get_drvdata(device);
>> +
>> +       reset_control_assert(dev->rstc);
>> +
>> +       clk_disable_unprepare(dev->ram_clk);
>> +       clk_disable_unprepare(dev->mod_clk);
>> +       clk_disable_unprepare(dev->ahb_clk);
>> +
> 
> You can use clk_bulk API here.

Since this change is already tested, I'd prefer to do that as a separate patch.

>> +       return 0;
>> +}
>> +
>> +int cedrus_hw_resume(struct device *device)
>> +{
>> +       struct cedrus_dev *dev = dev_get_drvdata(device);
>> +       int ret;
>> +
>> +       ret = clk_prepare_enable(dev->ahb_clk);
>> +       if (ret) {
>> +               dev_err(dev->dev, "Failed to enable AHB clock\n");
>> +
>> +               return ret;
>> +       }
>> +
>> +       ret = clk_prepare_enable(dev->mod_clk);
>> +       if (ret) {
>> +               dev_err(dev->dev, "Failed to enable MOD clock\n");
>> +
>> +               goto err_ahb_clk;
>> +       }
>> +
>> +       ret = clk_prepare_enable(dev->ram_clk);
>> +       if (ret) {
>> +               dev_err(dev->dev, "Failed to enable RAM clock\n");
>> +
>> +               goto err_mod_clk;
>> +       }
>> +
>> +       ret = reset_control_reset(dev->rstc);
>> +       if (ret) {
>> +               dev_err(dev->dev, "Failed to apply reset\n");
>> +
>> +               goto err_ram_clk;
>> +       }
>> +
>> +       return 0;
>> +
>> +err_ram_clk:
>> +       clk_disable_unprepare(dev->ram_clk);
>> +err_mod_clk:
>> +       clk_disable_unprepare(dev->mod_clk);
>> +err_ahb_clk:
>> +       clk_disable_unprepare(dev->ahb_clk);
>> +
>> +       return ret;
>> +}
>> +
>>  int cedrus_hw_probe(struct cedrus_dev *dev)
>>  {
>>         const struct cedrus_variant *variant;
>> @@ -236,42 +295,17 @@ int cedrus_hw_probe(struct cedrus_dev *dev)
>>                 goto err_sram;
>>         }
>>
>> -       ret = clk_prepare_enable(dev->ahb_clk);
>> -       if (ret) {
>> -               dev_err(dev->dev, "Failed to enable AHB clock\n");
>> -
>> -               goto err_sram;
>> -       }
>> -
>> -       ret = clk_prepare_enable(dev->mod_clk);
>> -       if (ret) {
>> -               dev_err(dev->dev, "Failed to enable MOD clock\n");
>> -
>> -               goto err_ahb_clk;
>> -       }
>> -
>> -       ret = clk_prepare_enable(dev->ram_clk);
>> -       if (ret) {
>> -               dev_err(dev->dev, "Failed to enable RAM clock\n");
>> -
>> -               goto err_mod_clk;
>> -       }
>> -
>> -       ret = reset_control_reset(dev->rstc);
>> -       if (ret) {
>> -               dev_err(dev->dev, "Failed to apply reset\n");
>> -
>> -               goto err_ram_clk;
>> +       pm_runtime_enable(dev->dev);
>> +       if (!pm_runtime_enabled(dev->dev)) {
>> +               ret = cedrus_hw_resume(dev->dev);
>> +               if (ret)
>> +                       goto err_pm;
>>         }
>>
>>         return 0;
>>
>> -err_ram_clk:
>> -       clk_disable_unprepare(dev->ram_clk);
>> -err_mod_clk:
>> -       clk_disable_unprepare(dev->mod_clk);
>> -err_ahb_clk:
>> -       clk_disable_unprepare(dev->ahb_clk);
>> +err_pm:
>> +       pm_runtime_disable(dev->dev);
>>  err_sram:
>>         sunxi_sram_release(dev->dev);
>>  err_mem:
>> @@ -282,11 +316,9 @@ int cedrus_hw_probe(struct cedrus_dev *dev)
>>
>>  void cedrus_hw_remove(struct cedrus_dev *dev)
>>  {
>> -       reset_control_assert(dev->rstc);
>> -
>> -       clk_disable_unprepare(dev->ram_clk);
>> -       clk_disable_unprepare(dev->mod_clk);
>> -       clk_disable_unprepare(dev->ahb_clk);
>> +       pm_runtime_disable(dev->dev);
>> +       if (!pm_runtime_status_suspended(dev->dev))
>> +               cedrus_hw_suspend(dev->dev);
>>
>>         sunxi_sram_release(dev->dev);
>>
>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_hw.h b/drivers/staging/media/sunxi/cedrus/cedrus_hw.h
>> index 604ff932fbf5..45f641f0bfa2 100644
>> --- a/drivers/staging/media/sunxi/cedrus/cedrus_hw.h
>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_hw.h
>> @@ -22,6 +22,9 @@ void cedrus_engine_disable(struct cedrus_dev *dev);
>>  void cedrus_dst_format_set(struct cedrus_dev *dev,
>>                            struct v4l2_pix_format *fmt);
>>
>> +int cedrus_hw_suspend(struct device *device);
>> +int cedrus_hw_resume(struct device *device);
>> +
>>  int cedrus_hw_probe(struct cedrus_dev *dev);
>>  void cedrus_hw_remove(struct cedrus_dev *dev);
>>
>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
>> index ed3f511f066f..16d82309e7b6 100644
>> --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
>> @@ -13,6 +13,8 @@
>>   * Marek Szyprowski, <m.szyprowski@...sung.com>
>>   */
>>
>> +#include <linux/pm_runtime.h>
>> +
>>  #include <media/videobuf2-dma-contig.h>
>>  #include <media/v4l2-device.h>
>>  #include <media/v4l2-ioctl.h>
>> @@ -450,12 +452,24 @@ static int cedrus_start_streaming(struct vb2_queue *vq, unsigned int count)
>>                 return -EINVAL;
>>         }
>>
>> -       if (V4L2_TYPE_IS_OUTPUT(vq->type) &&
>> -           dev->dec_ops[ctx->current_codec]->start)
>> -               ret = dev->dec_ops[ctx->current_codec]->start(ctx);
>> +       if (V4L2_TYPE_IS_OUTPUT(vq->type)) {
>> +               ret = pm_runtime_get_sync(dev->dev);
> 
> It's entirely up to you, but you could do get_sync/put
> between .device_run, as everything should happen
> in the context of v4l2_m2m_ops.device_run.
> (In that case, I believe you'd want to enable autosuspend.)
> 
> Not sure there's much to gain from an power consumption
> pov, though.

Agreed. Either you have a short autosuspend delay, and get per-frame latency; or
a longer delay, and the hardware is on for the entire stream anyway. So I don't
think it's worth the overhead.

> With the Originally-by changed:
> 
> Reviewed-by: Ezequiel Garcia <ezequiel@...labora.com>
> 
> Thanks,
> Ezequiel
> 

Thanks,
Samuel

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