linux-kernel - Re: [PATCH V12 8/9] cxl/port: Retry reading CDAT on failure

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Date:   Wed, 29 Jun 2022 20:40:27 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Alison Schofield <alison.schofield@...el.com>,
        Lukas Wunner <lukas@...ner.de>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>
Subject: Re: [PATCH V12 8/9] cxl/port: Retry reading CDAT on failure

On Tue, Jun 28, 2022 at 03:57:20PM +0100, Jonathan Cameron wrote:
> On Mon, 27 Jun 2022 21:15:26 -0700
> ira.weiny@...el.com wrote:
> 

[snip]

> >  
> > -/**
> > - * read_cdat_data - Read the CDAT data on this port
> > - * @port: Port to read data from
> > - *
> > - * This call will sleep waiting for responses from the DOE mailbox.
> > - */
> > -void read_cdat_data(struct cxl_port *port)
> > +static int __read_cdat_data(struct cxl_port *port)
> >  {
> >  	static struct pci_doe_mb *cdat_mb;
> >  	struct device *dev = &port->dev;
> >  	struct device *uport = port->uport;
> >  	size_t cdat_length;
> > -	int ret;
> > +	int ret = 0;
> Fairly sure there isn't a path in which ret isn't set...
> 

Yep.

> 
> Mixing ret and rc is a bit inconsistent, maybe scrub patch set for
> one or the other. (My fault originally I think :)

Ok PCI uses both ret and rc.  :-(  But CXL seems to be consistent with rc.  So
I've used rc with the new series which I think satisfies both subsystems.

Thanks again for the detail review of the series.  Hopefully there will be a
new version out tomorrow.
Ira

> 
> 
> >  
> >  	cdat_mb = find_cdat_mb(uport);
> >  	if (!cdat_mb) {
> >  		dev_dbg(dev, "No CDAT mailbox\n");
> > -		return;
> > +		return -EIO;
> >  	}
> >  
> >  	port->cdat_sup = true;
> >  
> >  	if (cxl_cdat_get_length(dev, cdat_mb, &cdat_length)) {
> >  		dev_dbg(dev, "No CDAT length\n");
> > -		return;
> > +		return -EIO;
> >  	}
> >  
> >  	port->cdat.table = devm_kzalloc(dev, cdat_length, GFP_KERNEL);
> >  	if (!port->cdat.table)
> > -		return;
> > +		return -ENOMEM;
> >  
> >  	port->cdat.length = cdat_length;
> >  	ret = cxl_cdat_read_table(dev, cdat_mb, &port->cdat);
> > @@ -658,5 +652,30 @@ void read_cdat_data(struct cxl_port *port)
> >  		port->cdat.length = 0;
> >  		dev_err(dev, "CDAT data read error\n");
> >  	}
> > +
> > +	return ret;
> > +}
> > +
> > +/**
> > + * read_cdat_data - Read the CDAT data on this port
> > + * @port: Port to read data from
> > + *
> > + * This call will sleep waiting for responses from the DOE mailbox.
> > + */
> > +void read_cdat_data(struct cxl_port *port)
> > +{
> > +	int retries = 5;
> > +	int rc;
> > +
> > +	while (retries--) {
> > +		rc = __read_cdat_data(port);
> > +		if (!rc)
> > +			return;
> > +		dev_dbg(&port->dev,
> > +			"CDAT data read error rc=%d (retries %d)\n",
> > +			rc, retries);
> > +	}
> > +	dev_err(&port->dev, "CDAT data read failed after %d retries\n",
> > +		retries);
> >  }
> >  EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);
>