[PATCH 5.18 551/879] cxl/pci: Make cxl_dvsec_ranges() failure not fatal to cxl_pci

Greg Kroah-Hartman
2022-06-08T00:38:26Z

From: Dan Williams <dan.j.williams@intel.com>

[ Upstream commit 36bfc6ad508af38f212cf5a38147d867fb3f80a8 ]

cxl_dvsec_ranges(), the helper for enumerating the presence of an active
legacy CXL.mem configuration on a CXL 2.0 Memory Expander, is not fatal
for cxl_pci because there is still value to enable mailbox operations
even if CXL.mem operation is disabled. Recall that the reason cxl_pci
does this initialization and not cxl_mem is to preserve the useful
property (for unit testing) that cxl_mem is cxl_memdev + mmio generic,
and does not require access to a 'struct pci_dev' to issue config
cycles.

Update 'struct cxl_endpoint_dvsec_info' to carry either a positive
number of non-zero size legacy CXL DVSEC ranges, or the negative error
code from __cxl_dvsec_ranges() in its @ranges member.

Reported-by: Krzysztof Zach <krzysztof.zach@intel.com>
Fixes: 560f78559006 ("cxl/pci: Retrieve CXL DVSEC memory info")
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lore.kernel.org/r/164730735869.3806189.4032428192652531946.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/cxl/pci.c | 27 ++++++++++++++++++---------
1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index c4941a3ca6a8..bb92853c3b93 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -462,13 +462,18 @@ static int wait_for_media_ready(struct cxl_dev_state *cxlds)
return 0;
}

-static int cxl_dvsec_ranges(struct cxl_dev_state *cxlds)
+/*
+ * Return positive number of non-zero ranges on success and a negative
+ * error code on failure. The cxl_mem driver depends on ranges == 0 to
+ * init HDM operation.
+ */
+static int __cxl_dvsec_ranges(struct cxl_dev_state *cxlds,
+ struct cxl_endpoint_dvsec_info *info)
{
- struct cxl_endpoint_dvsec_info *info = &cxlds->info;
struct pci_dev *pdev = to_pci_dev(cxlds->dev);
+ int hdm_count, rc, i, ranges = 0;
struct device *dev = &pdev->dev;
int d = cxlds->cxl_dvsec;
- int hdm_count, rc, i;
u16 cap, ctrl;

if (!d) {
@@ -545,10 +550,17 @@ static int cxl_dvsec_ranges(struct cxl_dev_state *cxlds)
};

if (size)
- info->ranges++;
+ ranges++;
}

- return 0;
+ return ranges;
+}
+
+static void cxl_dvsec_ranges(struct cxl_dev_state *cxlds)
+{
+ struct cxl_endpoint_dvsec_info *info = &cxlds->info;
+
+ info->ranges = __cxl_dvsec_ranges(cxlds, info);
}

static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
@@ -617,10 +629,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
if (rc)
return rc;

- rc = cxl_dvsec_ranges(cxlds);
- if (rc)
- dev_warn(&pdev->dev,
- "Failed to get DVSEC range information (%d)\n", rc);
+ cxl_dvsec_ranges(cxlds);

cxlmd = devm_cxl_add_memdev(cxlds);
if (IS_ERR(cxlmd))
--
2.35.1