linux-kernel - [PATCH v5 5/7] r8169: Reduce spinlock contention for the start of RTL8117

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Message-Id: <20231029183600.451694-5-mirsad.todorovac@alu.unizg.hr>
Date:   Sun, 29 Oct 2023 19:36:03 +0100
From:   Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To:     Jason Gunthorpe <jgg@...pe.ca>, Joerg Roedel <jroedel@...e.de>,
        Lu Baolu <baolu.lu@...ux.intel.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Heiner Kallweit <hkallweit1@...il.com>, nic_swsd@...ltek.com,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>,
        Marco Elver <elver@...gle.com>
Subject: [PATCH v5 5/7] r8169: Reduce spinlock contention for the start of RTL8117

Repeated calls to r8168_mac_ocp_write() and r8168_mac_ocp_modify()
in the startup of RTL8168ep involve implicit spin_lock_irqsave() and
spin_unlock_irqrestore() on each invocation.

This is avoided by grouping unlocked __r8168_mac_ocp_write() and
__r8168_mac_ocp_modify() primitives enclosed in the explicit
spin_lock_irqsave()/spin_unlock_irqrestore() pair.

Even if the lock is not contended, the check requires a LOCK CMPXCHG
or a similar instruction, which prevents all cores from accessing the
memory bus.

Fixes: 1287723aa139b ("r8169: add support for RTL8117")
Cc: Heiner Kallweit <hkallweit1@...il.com>
Cc: Marco Elver <elver@...gle.com>
Cc: nic_swsd@...ltek.com
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Link: https://lore.kernel.org/lkml/20231028005153.2180411-1-mirsad.todorovac@alu.unizg.hr/
Link: https://lore.kernel.org/lkml/20231028110459.2644926-1-mirsad.todorovac@alu.unizg.hr/
Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
---
v5:
 added unlocked primitives to allow mac ocs modify grouping
 applied coalescing of mac ocp writes/modifies for 8168ep and 8117
 some formatting fixes to please checkpatch.pl

v4:
 fixed complaints as advised by Heiner and checkpatch.pl
 split the patch into five sections to be more easily manipulated and reviewed
 introduced r8168_mac_ocp_write_seq()
 applied coalescing of mac ocp writes/modifies for 8168H, 8125 and 8125B

v3:
 removed register/mask pair array sentinels, so using ARRAY_SIZE().
 avoided duplication of RTL_W32() call code as advised by Heiner.

 drivers/net/ethernet/realtek/r8169_main.c | 24 ++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index 27016aaeb6a0..50fbacb05953 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -3348,7 +3348,15 @@ static void rtl_hw_start_8117(struct rtl8169_private *tp)
 		{ 0x19, 0x0040,	0x1100 },
 		{ 0x59, 0x0040,	0x1100 },
 	};
+
+	static const struct e_info_regdata e_info_8117_wr_1[] = {
+		{ 0xe63e, 0x0001 },
+		{ 0xe63e, 0x0000 },
+		{ 0xc094, 0x0000 },
+		{ 0xc09e, 0x0000 },
+	};
 	int rg_saw_cnt;
+	unsigned long flags;
 
 	rtl8168ep_stop_cmac(tp);
 	rtl_ephy_init(tp, e_info_8117);
@@ -3388,15 +3396,13 @@ static void rtl_hw_start_8117(struct rtl8169_private *tp)
 		r8168_mac_ocp_modify(tp, 0xd412, 0x0fff, sw_cnt_1ms_ini);
 	}
 
-	r8168_mac_ocp_modify(tp, 0xe056, 0x00f0, 0x0070);
-	r8168_mac_ocp_write(tp, 0xea80, 0x0003);
-	r8168_mac_ocp_modify(tp, 0xe052, 0x0000, 0x0009);
-	r8168_mac_ocp_modify(tp, 0xd420, 0x0fff, 0x047f);
-
-	r8168_mac_ocp_write(tp, 0xe63e, 0x0001);
-	r8168_mac_ocp_write(tp, 0xe63e, 0x0000);
-	r8168_mac_ocp_write(tp, 0xc094, 0x0000);
-	r8168_mac_ocp_write(tp, 0xc09e, 0x0000);
+	raw_spin_lock_irqsave(&tp->mac_ocp_lock, flags);
+	__r8168_mac_ocp_modify(tp, 0xe056, 0x00f0, 0x0070);
+	__r8168_mac_ocp_write(tp, 0xea80, 0x0003);
+	__r8168_mac_ocp_modify(tp, 0xe052, 0x0000, 0x0009);
+	__r8168_mac_ocp_modify(tp, 0xd420, 0x0fff, 0x047f);
+	__r8168_mac_ocp_write_seq(tp, e_info_8117_wr_1);
+	raw_spin_unlock_irqrestore(&tp->mac_ocp_lock, flags);
 
 	/* firmware is for MAC only */
 	r8169_apply_firmware(tp);
-- 
2.34.1