linux-kernel - Re: [PATCH V8 09/10] cxl/mem: Retry reading CDAT on failure

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Date:   Wed, 27 Apr 2022 18:57:40 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     <ira.weiny@...el.com>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Alison Schofield <alison.schofield@...el.com>,
        "Vishal Verma" <vishal.l.verma@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>
Subject: Re: [PATCH V8 09/10] cxl/mem: Retry reading CDAT on failure

On Thu, 14 Apr 2022 13:32:36 -0700
ira.weiny@...el.com wrote:

> From: Ira Weiny <ira.weiny@...el.com>
> 
> 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

validated, retry if the CDAT read fails.

> fails.  For now 5 retries are implemented.
> 
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> 
> ---
> 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/pci.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index d7952156dd02..43cbc297079d 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -940,7 +940,7 @@ static void cxl_initialize_cdat_callbacks(struct cxl_dev_state *cxlds)
>  	cxlds->cdat_read_table = cxl_cdat_read_table;
>  }
>  
> -static int read_cdat_data(struct cxl_dev_state *cxlds)
> +static int __read_cdat_data(struct cxl_dev_state *cxlds)
>  {
>  	struct device *dev = cxlds->dev;
>  	size_t cdat_length;
> @@ -962,6 +962,21 @@ static int read_cdat_data(struct cxl_dev_state *cxlds)
>  	return ret;
>  }
>  
> +static void read_cdat_data(struct cxl_dev_state *cxlds)
> +{
> +	int retries = 5;
> +	int rc;
> +
> +	while (retries--) {
> +		rc = __read_cdat_data(cxlds);
> +		if (!rc)
> +			break;
> +		dev_err(cxlds->dev,
> +			"CDAT data read error rc=%d (retries %d)\n",
> +			rc, retries);
> +	}
> +}
> +
>  static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  {
>  	struct cxl_register_map map;
> @@ -1035,9 +1050,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	cxl_initialize_cdat_callbacks(cxlds);
>  
>  	/* Cache the data early to ensure is_visible() works */
> -	rc = read_cdat_data(cxlds);
> -	if (rc)
> -		dev_err(&pdev->dev, "CDAT data read error (%d)\n", rc);
> +	read_cdat_data(cxlds);
>  
>  	cxl_dvsec_ranges(cxlds);
>