linux-kernel - RE: [PATCH v3 6/9] cxl/pci: Do not ignore PCI config read errors in match_add

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Message-ID: <63753bc4649dd_12cdff29498@dwillia2-xfh.jf.intel.com.notmuch>
Date:   Wed, 16 Nov 2022 11:36:36 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Robert Richter <rrichter@....com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Ira Weiny" <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>
CC:     <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "Davidlohr Bueso" <dave@...olabs.net>,
        Dave Jiang <dave.jiang@...el.com>,
        Robert Richter <rrichter@....com>
Subject: RE: [PATCH v3 6/9] cxl/pci: Do not ignore PCI config read errors in
 match_add_dports()

Robert Richter wrote:
> The link capabilities of a PCI device are read when enumerating its
> dports. This is done by reading the PCI config space. If that fails
> port enumeration ignores that error. However, reading the PCI config
> space should reliably work.
> 
> To reduce some complexity to the code flow when factoring out parts of
> the code in match_add_dports() for later reuse, change this to throw
> an error.
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/cxl/core/pci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 0dbbe8d39b07..8271b8abde7a 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -47,7 +47,7 @@ static int match_add_dports(struct pci_dev *pdev, void *data)

match_add_dports() never comes into play in the RCH topology case. There
are no switch ports to handle and CXL host-bridges are only ever dports
in the RCH case.

I will post the cxl_test enabling for an RCH topology so we can compare
notes there.