releases/6.13.7/hwmon-peci-dimmtemp-do-not-provide-fake-thresholds-data.patch

From 5797c04400ee117bfe459ff1e468d0ea38054ab4 Mon Sep 17 00:00:00 2001
From: Paul Fertser <fercerpav@gmail.com>
Date: Thu, 23 Jan 2025 15:20:02 +0300
Subject: hwmon: (peci/dimmtemp) Do not provide fake thresholds data

From: Paul Fertser <fercerpav@gmail.com>

commit 5797c04400ee117bfe459ff1e468d0ea38054ab4 upstream.

When an Icelake or Sapphire Rapids CPU isn't providing the maximum and
critical thresholds for particular DIMM the driver should return an
error to the userspace instead of giving it stale (best case) or wrong
(the structure contains all zeros after kzalloc() call) data.

The issue can be reproduced by binding the peci driver while the host is
fully booted and idle, this makes PECI interaction unreliable enough.

Fixes: 73bc1b885dae ("hwmon: peci: Add dimmtemp driver")
Fixes: 621995b6d795 ("hwmon: (peci/dimmtemp) Add Sapphire Rapids support")
Cc: stable@vger.kernel.org
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-by: Iwona Winiarska <iwona.winiarska@intel.com>
Link: https://lore.kernel.org/r/20250123122003.6010-1-fercerpav@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/hwmon/peci/dimmtemp.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

--- a/drivers/hwmon/peci/dimmtemp.c
+++ b/drivers/hwmon/peci/dimmtemp.c
@@ -127,8 +127,6 @@ static int update_thresholds(struct peci
 		return 0;
 
 	ret = priv->gen_info->read_thresholds(priv, dimm_order, chan_rank, &data);
-	if (ret == -ENODATA) /* Use default or previous value */
-		return 0;
 	if (ret)
 		return ret;
 
@@ -509,11 +507,11 @@ read_thresholds_icx(struct peci_dimmtemp
 
 	ret = peci_ep_pci_local_read(priv->peci_dev, 0, 13, 0, 2, 0xd4, &reg_val);
 	if (ret || !(reg_val & BIT(31)))
-		return -ENODATA; /* Use default or previous value */
+		return -ENODATA;
 
 	ret = peci_ep_pci_local_read(priv->peci_dev, 0, 13, 0, 2, 0xd0, &reg_val);
 	if (ret)
-		return -ENODATA; /* Use default or previous value */
+		return -ENODATA;
 
 	/*
 	 * Device 26, Offset 224e0: IMC 0 channel 0 -> rank 0
@@ -546,11 +544,11 @@ read_thresholds_spr(struct peci_dimmtemp
 
 	ret = peci_ep_pci_local_read(priv->peci_dev, 0, 30, 0, 2, 0xd4, &reg_val);
 	if (ret || !(reg_val & BIT(31)))
-		return -ENODATA; /* Use default or previous value */
+		return -ENODATA;
 
 	ret = peci_ep_pci_local_read(priv->peci_dev, 0, 30, 0, 2, 0xd0, &reg_val);
 	if (ret)
-		return -ENODATA; /* Use default or previous value */
+		return -ENODATA;
 
 	/*
 	 * Device 26, Offset 219a8: IMC 0 channel 0 -> rank 0