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

[Russ Weight <russell.h.weight@intel.com>]

On 9/17/20 1:28 PM, Tom Rix wrote:
> 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@intel.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.
Good catch. I'll give priority to -EINVAL in the next version of the
patch, as it is more informative in the context of this function.
>
>>  	/* 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 ?
Yilun addressed this question in his previous response. This isessentially a
reference count for nested disable calls. Weonly do the enable if the
disable count has gone to zero, so this isn't an error condition.
>>  
>>  	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.
Yilun and Hao addressed this comment in their previous responses. We are using the
'__' prefix to indicate highlight the fact caller needs to use care in managing
the locking associated with these functions.

Thanks,
- Russ
>
> Tom
>
>>  
>>  void afu_mmio_region_init(struct dfl_feature_platform_data *pdata);