Subject: Re: [PATCH v2] fpga: zynq-fpga: Enable pm_runtime (suspend, resume)
To: Moritz Fischer <moritz.fischer@ettus.com>, <atull@opensource.altera.com>
References: <1447970832-774-1-git-send-email-moritz.fischer@ettus.com>
CC: <gregkh@linuxfoundation.org>, <michal.simek@xilinx.com>,
        <linux-kernel@vger.kernel.org>, <soren.brinkmann@xilinx.com>,
        <linux-arm-kernel@lists.infradead.org>
From: Mike Looijmans <mike.looijmans@topic.nl>
Organization: TOPIC
Message-ID: <564ECAE7.9060900@topic.nl>
Date: Fri, 20 Nov 2015 08:25:27 +0100
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﻿On 19-11-15 23:07, Moritz Fischer wrote:
> Replaced constant clock_{enable,disable} calls with pm_runtime
> hooks for suspend and resume to avoid constant clk_enable /
> clk_disable.
>
> Acked-by: Alan Tull <atull@opensource.altera.com>
> Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
> ---
> Changes:
>
> v1:
>    - Removed superfluous #ifdef CONFIG_PM as suggested by Michal
>    - Changed commit message to include suspend / resume
>    - Added Alan's Acked-by
>
>   drivers/fpga/zynq-fpga.c | 76 +++++++++++++++++++++++++++++++++++++-----------
>   1 file changed, 59 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/fpga/zynq-fpga.c b/drivers/fpga/zynq-fpga.c
> index c2fb412..3f5469d 100644
> --- a/drivers/fpga/zynq-fpga.c
> +++ b/drivers/fpga/zynq-fpga.c
> @@ -28,6 +28,7 @@
>   #include <linux/of_address.h>
>   #include <linux/of_irq.h>
>   #include <linux/pm.h>
> +#include <linux/pm_runtime.h>
>   #include <linux/regmap.h>
>   #include <linux/string.h>
>
> @@ -184,8 +185,8 @@ static int zynq_fpga_ops_write_init(struct fpga_manager *mgr, u32 flags,
>
>   	priv = mgr->priv;
>
> -	err = clk_enable(priv->clk);
> -	if (err)
> +	err = pm_runtime_get_sync(priv->dev);
> +	if (err < 0)
>   		return err;
>
>   	/* don't globally reset PL if we're doing partial reconfig */
> @@ -271,12 +272,12 @@ static int zynq_fpga_ops_write_init(struct fpga_manager *mgr, u32 flags,
>   	ctrl = zynq_fpga_read(priv, MCTRL_OFFSET);
>   	zynq_fpga_write(priv, MCTRL_OFFSET, (~MCTRL_PCAP_LPBK_MASK & ctrl));
>
> -	clk_disable(priv->clk);
> +	pm_runtime_put(priv->dev);
>
>   	return 0;
>
>   out_err:
> -	clk_disable(priv->clk);
> +	pm_runtime_put(priv->dev);
>
>   	return err;
>   }
> @@ -301,9 +302,8 @@ static int zynq_fpga_ops_write(struct fpga_manager *mgr,
>
>   	memcpy(kbuf, buf, count);
>
> -	/* enable clock */
> -	err = clk_enable(priv->clk);
> -	if (err)
> +	err = pm_runtime_get_sync(priv->dev);
> +	if (err < 0)
>   		goto out_free;
>
>   	zynq_fpga_write(priv, INT_STS_OFFSET, IXR_ALL_MASK);
> @@ -335,7 +335,7 @@ static int zynq_fpga_ops_write(struct fpga_manager *mgr,
>   		err = -EFAULT;
>   	}
>
> -	clk_disable(priv->clk);
> +	pm_runtime_put(priv->dev);
>
>   out_free:
>   	dma_free_coherent(priv->dev, in_count, kbuf, dma_addr);
> @@ -349,8 +349,8 @@ static int zynq_fpga_ops_write_complete(struct fpga_manager *mgr, u32 flags)
>   	int err;
>   	u32 intr_status;
>
> -	err = clk_enable(priv->clk);
> -	if (err)
> +	err = pm_runtime_get_sync(priv->dev);
> +	if (err < 0)
>   		return err;
>
>   	err = zynq_fpga_poll_timeout(priv, INT_STS_OFFSET, intr_status,
> @@ -358,7 +358,7 @@ static int zynq_fpga_ops_write_complete(struct fpga_manager *mgr, u32 flags)
>   				     INIT_POLL_DELAY,
>   				     INIT_POLL_TIMEOUT);
>
> -	clk_disable(priv->clk);
> +	pm_runtime_put(priv->dev);
>
>   	if (err)
>   		return err;
> @@ -385,12 +385,12 @@ static enum fpga_mgr_states zynq_fpga_ops_state(struct fpga_manager *mgr)
>
>   	priv = mgr->priv;
>
> -	err = clk_enable(priv->clk);
> -	if (err)
> +	err = pm_runtime_get_sync(priv->dev);
> +	if (err < 0)
>   		return FPGA_MGR_STATE_UNKNOWN;
>
>   	intr_status = zynq_fpga_read(priv, INT_STS_OFFSET);
> -	clk_disable(priv->clk);
> +	pm_runtime_put(priv->dev);
>
>   	if (intr_status & IXR_PCFG_DONE_MASK)
>   		return FPGA_MGR_STATE_OPERATING;
> @@ -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);
> +		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);
> +	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);

 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.

> +
> +	return 0;
> +}
> +
> +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);
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops zynq_fpga_pm_ops = {
> +	SET_RUNTIME_PM_OPS(zynq_fpga_runtime_suspend,
> +			   zynq_fpga_runtime_resume, NULL)
> +};
> +
>   #ifdef CONFIG_OF
>   static const struct of_device_id zynq_fpga_of_match[] = {
>   	{ .compatible = "xlnx,zynq-devcfg-1.0", },
> @@ -503,6 +544,7 @@ static struct platform_driver zynq_fpga_driver = {
>   	.driver = {
>   		.name = "zynq_fpga_manager",
>   		.of_match_table = of_match_ptr(zynq_fpga_of_match),
> +		.pm = &zynq_fpga_pm_ops,
>   	},
>   };
>
>


Kind regards,

Mike Looijmans
System Expert

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