linux-kernel - Re: [PATCH v2] fpga: zynq-fpga: Enable pm

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Message-ID: <565452DB.8000300@topic.nl>
Date:	Tue, 24 Nov 2015 13:06:51 +0100
From:	Mike Looijmans <mike.looijmans@...ic.nl>
To:	Moritz Fischer <moritz.fischer@...us.com>
CC:	Alan Tull <atull@...nsource.altera.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Michal Simek <michal.simek@...inx.com>,
	<linux-kernel@...r.kernel.org>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] fpga: zynq-fpga: Enable pm_runtime (suspend, resume)

On 23-11-15 23:02, Moritz Fischer wrote:
> Hi Mike,
>
> thanks for your feedback. I put what I think you suggested inline below.
>
> On Thu, Nov 19, 2015 at 11:25 PM, Mike Looijmans
> <mike.looijmans@...ic.nl> wrote:
>> On 19-11-15 23:07, Moritz Fischer wrote:
>
>>> @@ -457,19 +457,26 @@ static int zynq_fpga_probe(struct platform_device
>>> *pdev)
>>>                  return err;
>>>          }
>>>
>>> +       pm_runtime_get_noresume(&pdev->dev);
>>> +       pm_runtime_set_active(&pdev->dev);
>>> +       pm_runtime_enable(&pdev->dev);
>>> +
>>>          /* unlock the device */
>>>          zynq_fpga_write(priv, UNLOCK_OFFSET, UNLOCK_MASK);
>>>
>>> -       clk_disable(priv->clk);
>>>
>>>          err = fpga_mgr_register(dev, "Xilinx Zynq FPGA Manager",
>>>                                  &zynq_fpga_ops, priv);
>>>          if (err) {
>>>                  dev_err(dev, "unable to register FPGA manager");
>>> -               clk_unprepare(priv->clk);
>>> +               clk_disable_unprepare(priv->clk);
> - clk_disable_unprepare(priv->clk);
>>> +               pm_runtime_put_noidle(&pdev->dev);
>>> +               pm_runtime_disable(&pdev->dev);
>>>                  return err;
>>>          }
>>>
>>> +       pm_runtime_put(&pdev->dev);
>>> +
>>>          return 0;
>>>    }
>>>
>>> @@ -483,11 +490,45 @@ static int zynq_fpga_remove(struct platform_device
>>> *pdev)
>>>
>>>          fpga_mgr_unregister(&pdev->dev);
>>>
>>> -       clk_unprepare(priv->clk);
>>> +       pm_runtime_get_sync(&pdev->dev);
>>> +       clk_disable_unprepare(priv->clk);
> - clk_disable_unprepare(priv->clk);
>
>>> +       pm_runtime_put_noidle(&pdev->dev);
>>> +       pm_runtime_disable(&pdev->dev);
>>>
>>>          return 0;
>>>    }
>>>
>>> +static int __maybe_unused zynq_fpga_runtime_suspend(struct device *dev)
>>> +{
>>> +       struct zynq_fpga_priv *priv;
>>> +       struct fpga_manager *mgr;
>>> +
>>> +       mgr = dev_get_drvdata(dev);
>>> +       priv = mgr->priv;
>>> +
>>> +       clk_disable(priv->clk);
>
> - clk_disable(priv->clk)
> + clk_disable_unprepare(priv->clk)
>>
>>
>>  From what I understand, this call is done in a sleepable context, so you can
>> use clk_disable_unprepare here (and its counterpart in resume). And remove
>> the prepare at probe time and unprepare at removal.
>>
>> Not all clocks can implement atomic enable/disable, for example I2C and SPI
>> controlled clocks only implement the prepare/unprepare routines.
>>
>> I guess the "clk" here will always be a SOC provided one, so it won't make
>> any difference for the Zynq, but someone is likely to some day copy/paste
>> this driver and use it for some externally connected FPGA instead.
>
> To clarify. Is the above / below what you suggested?

Indeed, that's exactly what I meant.

>>> +static int __maybe_unused zynq_fpga_runtime_resume(struct device *dev)
>>> +{
>>> +       struct zynq_fpga_priv *priv;
>>> +       struct fpga_manager *mgr;
>>> +
>>> +       mgr = dev_get_drvdata(dev);
>>> +       priv = mgr->priv;
>>> +
>>> +       clk_enable(priv->clk);
>
> - clk_enable(priv->clk)
> + clk_prepare_enable(priv->clk)
>>> +
>>> +       return 0;
>>> +}
>>> +
>
> Cheers,
>
> Moritz
>



Kind regards,

Mike Looijmans
System Expert

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