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Date:   Wed, 3 Feb 2021 14:55:58 -0800
From:   Russ Weight <russell.h.weight@...el.com>
To:     "Wu, Hao" <hao.wu@...el.com>, "mdf@...nel.org" <mdf@...nel.org>,
        "linux-fpga@...r.kernel.org" <linux-fpga@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "trix@...hat.com" <trix@...hat.com>,
        "lgoncalv@...hat.com" <lgoncalv@...hat.com>,
        "Xu, Yilun" <yilun.xu@...el.com>,
        "Gerlach, Matthew" <matthew.gerlach@...el.com>
Subject: Re: [PATCH v3 1/1] fpga: dfl: afu: harden port enable logic



On 2/3/21 1:01 AM, Wu, Hao wrote:
>> Subject: [PATCH v3 1/1] fpga: dfl: afu: harden port enable logic
>>
>> 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>
>> ---
>> v3:
>>   - afu_port_err_clear() changed to prioritize port_enable failure over
>>     other a detected mismatch in port errors.
>>   - reorganized code in port_reset() to be more readable.
>> v2:
>>   - Fixed typo in commit message
>> ---
>>  drivers/fpga/dfl-afu-error.c |  8 ++++----
>>  drivers/fpga/dfl-afu-main.c  | 31 ++++++++++++++++++++++---------
>>  drivers/fpga/dfl-afu.h       |  2 +-
>>  3 files changed, 27 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/fpga/dfl-afu-error.c b/drivers/fpga/dfl-afu-error.c
>> index c4691187cca9..2ced610059cc 100644
>> --- a/drivers/fpga/dfl-afu-error.c
>> +++ b/drivers/fpga/dfl-afu-error.c
>> @@ -52,7 +52,7 @@ static int afu_port_err_clear(struct device *dev, u64 err)
>>  struct dfl_feature_platform_data *pdata = dev_get_platdata(dev);
>>  struct platform_device *pdev = to_platform_device(dev);
>>  void __iomem *base_err, *base_hdr;
>> -int ret = -EBUSY;
>> +int enable_ret = 0, ret = -EBUSY;
>>  u64 v;
>>
>>  base_err = dfl_get_feature_ioaddr_by_id(dev,
>> PORT_FEATURE_ID_ERROR);
>> @@ -102,12 +102,12 @@ static int afu_port_err_clear(struct device *dev, u64
>> err)
>>  /* Clear mask */
>>  __afu_port_err_mask(dev, false);
>>
>> -/* Enable the Port by clear the reset */
>> -__afu_port_enable(pdev);
>> +/* Enable the Port by clearing the reset */
>> +enable_ret = __afu_port_enable(pdev);
>>
>>  done:
>>  mutex_unlock(&pdata->lock);
>> -return ret;
>> +return enable_ret ? enable_ret : ret;
> Maybe we should add some error message to notify user, there are more errors happened,
> as some ret value is not returned.
It is the -EINVAL error case that would get lost if there was a double error.
This error indicates that the value written to sysfs by the user does not
correspond to the current port errors. This is not a hardware error, and could
even be a user error. Do you think a warning in the error log is needed here?

>
>>  }
>>
>>  static ssize_t errors_show(struct device *dev, struct device_attribute *attr,
>> diff --git a/drivers/fpga/dfl-afu-main.c b/drivers/fpga/dfl-afu-main.c
>> index 753cda4b2568..729eb306062e 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;
>>
>>  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");
> Maybe we can change dev_err message in port disable to "disable device" as well. : )
Thank you. I'll submit a new version of the patch with this fix.

- Russ
>
> Hao
>
>> +return -ETIMEDOUT;
>> +}
>> +
>> +return 0;
>> +}
>>
>>  /**
>>   * __afu_port_disable - disable a port by hold reset
>> @@ -111,9 +124,9 @@ static int __port_reset(struct platform_device *pdev)
>>
>>  ret = __afu_port_disable(pdev);
>>  if (!ret)
>> -__afu_port_enable(pdev);
>> +return ret;
>>
>> -return ret;
>> +return __afu_port_enable(pdev);
>>  }
>>
>>  static int port_reset(struct platform_device *pdev)
>> @@ -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);
>>
>>  void afu_mmio_region_init(struct dfl_feature_platform_data *pdata);
>> --
>> 2.25.1

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