hwmon: (peci/dimmtemp) Do not provide fake thresholds data

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: 73bc1b8 ("hwmon: peci: Add dimmtemp driver")
Fixes: 621995b ("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>

Author: paulfertser

drivers/hwmon/peci/dimmtemp.c

@@ -127,8 +127,6 @@ static int update_thresholds(struct peci_dimmtemp *priv, int dimm_no)
 		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 *priv, int dimm_order, int chan_rank, u
 
 	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 *priv, int dimm_order, int chan_rank, u
 
 	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