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Date:   Thu, 4 Feb 2021 01:38:18 +0000
From:   "Wu, Hao" <hao.wu@...el.com>
To:     "Weight, Russell H" <russell.h.weight@...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?

I think so, as there are actually two errors there, I feel it's better to let user know
their input is not accepted too than just keeping silence, right? as this error
should be triggered by user input?

Hao

> 
> >
> >>  }
> >>
> >>  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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