[PATCH v2 1/1] EDAC/i10nm: Skip the absent memory controllers

From: Qiuxu Zhuo
Date: Sun Jul 09 2023 - 21:38:10 EST


Some Sapphire Rapids workstations' absent memory controllers
still appear as PCIe devices that fool the i10nm_edac driver
and result in "shift exponent -66 is negative" call traces
from skx_get_dimm_info().

Skip the absent memory controllers to avoid the call traces.

Reported-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-edac/CAAd53p41Ku1m1rapeqb1xtD+kKuk+BaUW=dumuoF0ZO3GhFjFA@xxxxxxxxxxxxxx/T/#m5de16dce60a8c836ec235868c7c16e3fefad0cc2
Tested-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
Reported-by: Koba Ko <koba.ko@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-edac/SA1PR11MB71305B71CCCC3D9305835202892AA@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/T/#t
Tested-by: Koba Ko <koba.ko@xxxxxxxxxxxxx>
Fixes: d4dc89d069aa ("EDAC, i10nm: Add a driver for Intel 10nm server processors")
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
---
v1->v2:
- No function changes.
- s/exponet/exponent/ in the commit message.
- Add two tags of "Tested-by".

drivers/edac/i10nm_base.c | 54 +++++++++++++++++++++++++++++++++++----
1 file changed, 49 insertions(+), 5 deletions(-)

diff --git a/drivers/edac/i10nm_base.c b/drivers/edac/i10nm_base.c
index a897b6aff368..349ff6cfb379 100644
--- a/drivers/edac/i10nm_base.c
+++ b/drivers/edac/i10nm_base.c
@@ -658,13 +658,49 @@ static struct pci_dev *get_ddr_munit(struct skx_dev *d, int i, u32 *offset, unsi
return mdev;
}

+/**
+ * i10nm_imc_absent() - Check whether the memory controller @imc is absent
+ *
+ * @imc : The pointer to the structure of memory controller EDAC device.
+ *
+ * RETURNS : true if the memory controller EDAC device is absent, false otherwise.
+ */
+static bool i10nm_imc_absent(struct skx_imc *imc)
+{
+ u32 mcmtr;
+ int i;
+
+ switch (res_cfg->type) {
+ case SPR:
+ for (i = 0; i < res_cfg->ddr_chan_num; i++) {
+ mcmtr = I10NM_GET_MCMTR(imc, i);
+ edac_dbg(1, "ch%d mcmtr reg %x\n", i, mcmtr);
+ if (mcmtr != ~0)
+ return false;
+ }
+
+ /*
+ * Some workstations' absent memory controllers still
+ * appear as PCIe devices, misleading the EDAC driver.
+ * By observing that the MMIO registers of these absent
+ * memory controllers consistently hold the value of ~0.
+ *
+ * We identify a memory controller as absent by checking
+ * if its MMIO register "mcmtr" == ~0 in all its channels.
+ */
+ return true;
+ default:
+ return false;
+ }
+}
+
static int i10nm_get_ddr_munits(void)
{
struct pci_dev *mdev;
void __iomem *mbase;
unsigned long size;
struct skx_dev *d;
- int i, j = 0;
+ int i, lmc, j = 0;
u32 reg, off;
u64 base;

@@ -690,7 +726,7 @@ static int i10nm_get_ddr_munits(void)
edac_dbg(2, "socket%d mmio base 0x%llx (reg 0x%x)\n",
j++, base, reg);

- for (i = 0; i < res_cfg->ddr_imc_num; i++) {
+ for (lmc = 0, i = 0; i < res_cfg->ddr_imc_num; i++) {
mdev = get_ddr_munit(d, i, &off, &size);

if (i == 0 && !mdev) {
@@ -700,8 +736,6 @@ static int i10nm_get_ddr_munits(void)
if (!mdev)
continue;

- d->imc[i].mdev = mdev;
-
edac_dbg(2, "mc%d mmio base 0x%llx size 0x%lx (reg 0x%x)\n",
i, base + off, size, reg);

@@ -712,7 +746,17 @@ static int i10nm_get_ddr_munits(void)
return -ENODEV;
}

- d->imc[i].mbase = mbase;
+ d->imc[lmc].mbase = mbase;
+ if (i10nm_imc_absent(&d->imc[lmc])) {
+ pci_dev_put(mdev);
+ iounmap(mbase);
+ d->imc[lmc].mbase = NULL;
+ edac_dbg(2, "Skip absent mc%d\n", i);
+ continue;
+ } else {
+ d->imc[lmc].mdev = mdev;
+ lmc++;
+ }
}
}

--
2.17.1