Re: [PATCH v9 8/9] cxl/port: Retry reading CDAT on failure

[Davidlohr Bueso <dave@xxxxxxxxxxxx>]

On Tue, 31 May 2022, ira.weiny@xxxxxxxxx wrote:

> From: Ira Weiny <ira.weiny@xxxxxxxxx>
>
> The CDAT read may fail for a number of reasons but mainly it is possible
> to get different parts of a valid state.  The checksum in the CDAT table
> protects against this.
>
> Now that the cdat data is validated issue a retries if the CDAT read
> fails.  For now 5 retries are implemented.
>
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> ---
> Changes from V8
> 	Move code to cxl/core/pci.c
>
> Changes from V6
> 	Move to pci.c
> 	Fix retries count
> 	Change to 5 retries
>
> Changes from V5:
> 	New patch -- easy to push off or drop.
> ---
> drivers/cxl/core/pci.c | 32 +++++++++++++++++++++-----------
> 1 file changed, 21 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index bb370df1cb6c..7f7dac9030a6 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -620,20 +620,18 @@ static int cxl_cdat_read_table(struct cxl_port *port,
> 	return rc;
> }
>
> -void read_cdat_data(struct cxl_port *port)
> +static int __read_cdat_data(struct cxl_port *port)
> {
> 	struct device *dev = &port->dev;
> 	size_t cdat_length;
> 	int ret;
>
> 	if (cxl_cdat_get_length(port, &cdat_length))
> -		return;
> +		return 0;
>
> 	port->cdat.table = devm_kzalloc(dev, cdat_length, GFP_KERNEL);
> -	if (!port->cdat.table) {
> -		ret = -ENOMEM;
> -		goto error;
> -	}
> +	if (!port->cdat.table)
> +		return -ENOMEM;
>
> 	port->cdat.length = cdat_length;
> 	ret = cxl_cdat_read_table(port, &port->cdat);
> @@ -641,12 +639,24 @@ void read_cdat_data(struct cxl_port *port)
> 		devm_kfree(dev, port->cdat.table);
> 		port->cdat.table = NULL;
> 		port->cdat.length = 0;
> -		ret = -EIO;
> -		goto error;
> +		return -EIO;
> 	}
>
> -	return;
> -error:
> -	dev_err(dev, "CDAT data read error (%d)\n", ret);
> +	return 0;
> +}
> +
> +void read_cdat_data(struct cxl_port *port)
> +{
> +	int retries = 5;
> +	int rc;
> +
> +	while (retries--) {
> +		rc = __read_cdat_data(port);
> +		if (!rc)
> +			break;
> +		dev_err(&port->dev,
> +			"CDAT data read error rc=%d (retries %d)\n",
> +			rc, retries);
> +	}
> }
> EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);


Better a single final error message after exhausting all retries
instead of each time.

Thanks,
Davidlohr