linux-kernel - Re: [PATCH v2 1/1] fpga: dfl: afu: harden port enable logic

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Date:   Thu, 17 Sep 2020 13:28:22 -0700
From:   Tom Rix <trix@...hat.com>
To:     Russ Weight <russell.h.weight@...el.com>, mdf@...nel.org,
        linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     lgoncalv@...hat.com, yilun.xu@...el.com, hao.wu@...el.com,
        matthew.gerlach@...el.com
Subject: Re: [PATCH v2 1/1] fpga: dfl: afu: harden port enable logic


On 9/17/20 11:32 AM, Russ Weight wrote:
> Port enable is not complete until ACK = 0. Change
> __afu_port_enable() to guarantee that the enable process
> is complete by polling for ACK == 0.
>
> Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> ---
>  drivers/fpga/dfl-afu-error.c |  2 +-
>  drivers/fpga/dfl-afu-main.c  | 29 +++++++++++++++++++++--------
>  drivers/fpga/dfl-afu.h       |  2 +-
>  3 files changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/fpga/dfl-afu-error.c b/drivers/fpga/dfl-afu-error.c
> index c4691187cca9..0806532a3e9f 100644
> --- a/drivers/fpga/dfl-afu-error.c
> +++ b/drivers/fpga/dfl-afu-error.c
> @@ -103,7 +103,7 @@ static int afu_port_err_clear(struct device *dev, u64 err)
>  	__afu_port_err_mask(dev, false);
>  

There is an earlier bit that sets ret = -EINVAL.

This error will be lost or not handled well.

Right now it doesn't seem to be handled.

>  	/* Enable the Port by clear the reset */
> -	__afu_port_enable(pdev);
> +	ret = __afu_port_enable(pdev);
>  
>  done:
>  	mutex_unlock(&pdata->lock);
> diff --git a/drivers/fpga/dfl-afu-main.c b/drivers/fpga/dfl-afu-main.c
> index 753cda4b2568..f73b06cdf13c 100644
> --- a/drivers/fpga/dfl-afu-main.c
> +++ b/drivers/fpga/dfl-afu-main.c
> @@ -21,6 +21,9 @@
>  
>  #include "dfl-afu.h"
>  
> +#define RST_POLL_INVL 10 /* us */
> +#define RST_POLL_TIMEOUT 1000 /* us */
> +
>  /**
>   * __afu_port_enable - enable a port by clear reset
>   * @pdev: port platform device.
> @@ -32,7 +35,7 @@
>   *
>   * The caller needs to hold lock for protection.
>   */
> -void __afu_port_enable(struct platform_device *pdev)
> +int __afu_port_enable(struct platform_device *pdev)
>  {
>  	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
>  	void __iomem *base;
> @@ -41,7 +44,7 @@ void __afu_port_enable(struct platform_device *pdev)
>  	WARN_ON(!pdata->disable_count);
>  
>  	if (--pdata->disable_count != 0)
> -		return;
> +		return 0;
Is this really a success ? Maybe -EBUSY ?
>  
>  	base = dfl_get_feature_ioaddr_by_id(&pdev->dev, PORT_FEATURE_ID_HEADER);
>  
> @@ -49,10 +52,20 @@ void __afu_port_enable(struct platform_device *pdev)
>  	v = readq(base + PORT_HDR_CTRL);
>  	v &= ~PORT_CTRL_SFTRST;
>  	writeq(v, base + PORT_HDR_CTRL);
> -}
>  
> -#define RST_POLL_INVL 10 /* us */
> -#define RST_POLL_TIMEOUT 1000 /* us */
> +	/*
> +	 * HW clears the ack bit to indicate that the port is fully out
> +	 * of reset.
> +	 */
> +	if (readq_poll_timeout(base + PORT_HDR_CTRL, v,
> +			       !(v & PORT_CTRL_SFTRST_ACK),
> +			       RST_POLL_INVL, RST_POLL_TIMEOUT)) {
> +		dev_err(&pdev->dev, "timeout, failure to enable device\n");
> +		return -ETIMEDOUT;
> +	}
> +
> +	return 0;
> +}
>  
>  /**
>   * __afu_port_disable - disable a port by hold reset
> @@ -111,7 +124,7 @@ static int __port_reset(struct platform_device *pdev)
>  
>  	ret = __afu_port_disable(pdev);
>  	if (!ret)
> -		__afu_port_enable(pdev);
> +		ret = __afu_port_enable(pdev);
>  
>  	return ret;
>  }
> @@ -872,11 +885,11 @@ static int afu_dev_destroy(struct platform_device *pdev)
>  static int port_enable_set(struct platform_device *pdev, bool enable)
>  {
>  	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
> -	int ret = 0;
> +	int ret;
>  
>  	mutex_lock(&pdata->lock);
>  	if (enable)
> -		__afu_port_enable(pdev);
> +		ret = __afu_port_enable(pdev);
>  	else
>  		ret = __afu_port_disable(pdev);
>  	mutex_unlock(&pdata->lock);
> diff --git a/drivers/fpga/dfl-afu.h b/drivers/fpga/dfl-afu.h
> index 576e94960086..e5020e2b1f3d 100644
> --- a/drivers/fpga/dfl-afu.h
> +++ b/drivers/fpga/dfl-afu.h
> @@ -80,7 +80,7 @@ struct dfl_afu {
>  };
>  
>  /* hold pdata->lock when call __afu_port_enable/disable */
> -void __afu_port_enable(struct platform_device *pdev);
> +int __afu_port_enable(struct platform_device *pdev);
>  int __afu_port_disable(struct platform_device *pdev);

The other functions in this file have afu_*  since the __afu_port_enable/disable

are used other places would it make sense to remove the '__' prefix ?

If you think so, maybe a cleanup patch later.

Tom

>  
>  void afu_mmio_region_init(struct dfl_feature_platform_data *pdata);