[PATCH AUTOSEL 6.6 182/294] EDAC/ie31200: work around false positive build warning

Sasha Levin
2025-05-05T23:02:35Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit c29dfd661fe2f8d1b48c7f00590929c04b25bf40 ]

gcc-14 produces a bogus warning in some configurations:

drivers/edac/ie31200_edac.c: In function 'ie31200_probe1.isra':
drivers/edac/ie31200_edac.c:412:26: error: 'dimm_info' is used uninitialized [-Werror=uninitialized]
412 | struct dimm_data dimm_info[IE31200_CHANNELS][IE31200_DIMMS_PER_CHANNEL];
| ^~~~~~~~~
drivers/edac/ie31200_edac.c:412:26: note: 'dimm_info' declared here
412 | struct dimm_data dimm_info[IE31200_CHANNELS][IE31200_DIMMS_PER_CHANNEL];
| ^~~~~~~~~

I don't see any way the unintialized access could really happen here,
but I can see why the compiler gets confused by the two loops.

Instead, rework the two nested loops to only read the addr_decode
registers and then keep only one instance of the dimm info structure.

[Tony: Qiuxu pointed out that the "populate DIMM info" comment was left
behind in the refactor and suggested moving it. I deleted the comment
as unnecessry in front os a call to populate_dimm_info(). That seems
pretty self-describing.]

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/all/20250122065031.1321015-1-arnd@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/edac/ie31200_edac.c | 28 +++++++++++++---------------
1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/edac/ie31200_edac.c b/drivers/edac/ie31200_edac.c
index 56be8ef40f376..e3635fba63b49 100644
--- a/drivers/edac/ie31200_edac.c
+++ b/drivers/edac/ie31200_edac.c
@@ -405,10 +405,9 @@ static int ie31200_probe1(struct pci_dev *pdev, int dev_idx)
int i, j, ret;
struct mem_ctl_info *mci = NULL;
struct edac_mc_layer layers[2];
- struct dimm_data dimm_info[IE31200_CHANNELS][IE31200_DIMMS_PER_CHANNEL];
void __iomem *window;
struct ie31200_priv *priv;
- u32 addr_decode, mad_offset;
+ u32 addr_decode[IE31200_CHANNELS], mad_offset;

/*
* Kaby Lake, Coffee Lake seem to work like Skylake. Please re-visit
@@ -466,19 +465,10 @@ static int ie31200_probe1(struct pci_dev *pdev, int dev_idx)
mad_offset = IE31200_MAD_DIMM_0_OFFSET;
}

- /* populate DIMM info */
for (i = 0; i < IE31200_CHANNELS; i++) {
- addr_decode = readl(window + mad_offset +
+ addr_decode[i] = readl(window + mad_offset +
(i * 4));
- edac_dbg(0, "addr_decode: 0x%x\n", addr_decode);
- for (j = 0; j < IE31200_DIMMS_PER_CHANNEL; j++) {
- populate_dimm_info(&dimm_info[i][j], addr_decode, j,
- skl);
- edac_dbg(0, "size: 0x%x, rank: %d, width: %d\n",
- dimm_info[i][j].size,
- dimm_info[i][j].dual_rank,
- dimm_info[i][j].x16_width);
- }
+ edac_dbg(0, "addr_decode: 0x%x\n", addr_decode[i]);
}

/*
@@ -489,14 +479,22 @@ static int ie31200_probe1(struct pci_dev *pdev, int dev_idx)
*/
for (i = 0; i < IE31200_DIMMS_PER_CHANNEL; i++) {
for (j = 0; j < IE31200_CHANNELS; j++) {
+ struct dimm_data dimm_info;
struct dimm_info *dimm;
unsigned long nr_pages;

- nr_pages = IE31200_PAGES(dimm_info[j][i].size, skl);
+ populate_dimm_info(&dimm_info, addr_decode[j], i,
+ skl);
+ edac_dbg(0, "size: 0x%x, rank: %d, width: %d\n",
+ dimm_info.size,
+ dimm_info.dual_rank,
+ dimm_info.x16_width);
+
+ nr_pages = IE31200_PAGES(dimm_info.size, skl);
if (nr_pages == 0)
continue;

- if (dimm_info[j][i].dual_rank) {
+ if (dimm_info.dual_rank) {
nr_pages = nr_pages / 2;
dimm = edac_get_dimm(mci, (i * 2) + 1, j, 0);
dimm->nr_pages = nr_pages;
--
2.39.5