From: jsg <jsg@openbsd.org>
Date: Thu, 23 Jun 2022 09:47:04 +0000 (+0000)
Subject: ungate DMA clock on >= tgp to avoid packet loss on Alder Lake
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=b3e30c103e1fbbcabc430d676b5da2c1e1e73281;p=openbsd

ungate DMA clock on >= tgp to avoid packet loss on Alder Lake
chicken bit set in linux but not documented anywhere I can find
ok claudio@
---

diff --git a/sys/dev/pci/if_em_hw.c b/sys/dev/pci/if_em_hw.c
index 727c431921d..6d230587e99 100644
--- a/sys/dev/pci/if_em_hw.c
+++ b/sys/dev/pci/if_em_hw.c
@@ -31,7 +31,7 @@
 
 *******************************************************************************/
 
-/* $OpenBSD: if_em_hw.c,v 1.115 2022/06/23 09:38:28 jsg Exp $ */
+/* $OpenBSD: if_em_hw.c,v 1.116 2022/06/23 09:47:04 jsg Exp $ */
 /*
  * if_em_hw.c Shared functions for accessing and configuring the MAC
  */
@@ -1846,6 +1846,13 @@ em_init_hw(struct em_softc *sc)
 		em_set_pci_ex_no_snoop(hw, snoop);
 	}
 
+	/* ungate DMA clock to avoid packet loss */
+	if (hw->mac_type >= em_pch_tgp) {
+		uint32_t fflt_dbg = E1000_READ_REG(hw, FFLT_DBG);
+		fflt_dbg |= (1 << 12);
+		E1000_WRITE_REG(hw, FFLT_DBG, fflt_dbg);
+	}
+
 	if (hw->device_id == E1000_DEV_ID_82546GB_QUAD_COPPER ||
 	    hw->device_id == E1000_DEV_ID_82546GB_QUAD_COPPER_KSP3) {
 		ctrl_ext = E1000_READ_REG(hw, CTRL_EXT);