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

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Message-Id: <20220607165018.860048093@linuxfoundation.org>
Date:   Tue,  7 Jun 2022 19:01:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Krzysztof Zach <krzysztof.zach@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dan Williams <dan.j.williams@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 551/879] cxl/pci: Make cxl_dvsec_ranges() failure not fatal to cxl_pci

From: Dan Williams <dan.j.williams@...el.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@...el.com>
Fixes: 560f78559006 ("cxl/pci: Retrieve CXL DVSEC memory info")
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Reviewed-by: Davidlohr Bueso <dave@...olabs.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@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.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