[PATCH 6.18 223/314] e1000e: clear DPG_EN after reset to avoid autonomous power-gating

Sasha Levin
2026-03-10T11:28:55Z

From: Vitaly Lifshits <vitaly.lifshits@intel.com>

[ Upstream commit 0942fc6d324eb9c6b16187b2aa994c0823557f06 ]

Panther Lake systems introduced an autonomous power gating feature for
the integrated Gigabit Ethernet in shutdown state (S5) state. As part of
it, the reset value of DPG_EN bit was changed to 1. Clear this bit after
performing hardware reset to avoid errors such as Tx/Rx hangs, or packet
loss/corruption.

Fixes: 0c9183ce61bc ("e1000e: Add support for the next LOM generation")
Signed-off-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Avigail Dahan <avigailx.dahan@intel.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/intel/e1000e/defines.h | 1 +
drivers/net/ethernet/intel/e1000e/ich8lan.c | 9 +++++++++
2 files changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000e/defines.h b/drivers/net/ethernet/intel/e1000e/defines.h
index ba331899d1861..d4a1041e456dc 100644
--- a/drivers/net/ethernet/intel/e1000e/defines.h
+++ b/drivers/net/ethernet/intel/e1000e/defines.h
@@ -33,6 +33,7 @@

/* Extended Device Control */
#define E1000_CTRL_EXT_LPCD 0x00000004 /* LCD Power Cycle Done */
+#define E1000_CTRL_EXT_DPG_EN 0x00000008 /* Dynamic Power Gating Enable */
#define E1000_CTRL_EXT_SDP3_DATA 0x00000080 /* Value of SW Definable Pin 3 */
#define E1000_CTRL_EXT_FORCE_SMBUS 0x00000800 /* Force SMBus mode */
#define E1000_CTRL_EXT_EE_RST 0x00002000 /* Reinitialize from EEPROM */
diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
index df4e7d781cb1c..f9328caefe44b 100644
--- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
+++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
@@ -4925,6 +4925,15 @@ static s32 e1000_reset_hw_ich8lan(struct e1000_hw *hw)
reg |= E1000_KABGTXD_BGSQLBIAS;
ew32(KABGTXD, reg);

+ /* The hardware reset value of the DPG_EN bit is 1.
+ * Clear DPG_EN to prevent unexpected autonomous power gating.
+ */
+ if (hw->mac.type >= e1000_pch_ptp) {
+ reg = er32(CTRL_EXT);
+ reg &= ~E1000_CTRL_EXT_DPG_EN;
+ ew32(CTRL_EXT, reg);
+ }
+
return 0;
}

--
2.51.0