netdev - [PATCH net] gianfar: Don't force RGMII mode after reset, use defaults

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Date:   Tue, 12 Nov 2019 16:55:11 +0200
From:   Claudiu Manoil <claudiu.manoil@....com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, danielwa@...co.com
Subject: [PATCH net] gianfar: Don't force RGMII mode after reset, use defaults

We received reports that forcing the MAC into RGMII (1 Gbps)
interface mode after MAC reset occasionally disrupts operation
of PHYs capable only of 100Mbps, even after adjust_link kicks
in and re-adjusts the interface mode in MACCFG2 accordingly.
Instead of forcing MACCFG2 into RGMII mode, let's use the default
reset value of MACCFG2 (that leaves the IF_Mode field unset) and
let adjust_link configure the correct mode from the beginning.
MACCFG2_INIT_SETTINGS is dropped, only the PAD_CRC bit is preserved,
the remaining fields (IF_Mode and Duplex) are left for adjust_link.
Tested on boards with gigabit PHYs.

MACCFG2_INIT_SETTINGS is there since day one, but the issue
got visible after introducing the MAC reset and reconfig support,
which added MAC reset at runtime, at interface open.

Fixes: a328ac92d314 ("gianfar: Implement MAC reset and reconfig procedure")

Reported-by: Daniel Walker <danielwa@...co.com>
Signed-off-by: Claudiu Manoil <claudiu.manoil@....com>
---
 drivers/net/ethernet/freescale/gianfar.c | 3 ++-
 drivers/net/ethernet/freescale/gianfar.h | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 51ad864..0f4d13d 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -3173,7 +3173,8 @@ void gfar_mac_reset(struct gfar_private *priv)
 	gfar_write(&regs->minflr, MINFLR_INIT_SETTINGS);

 	/* Initialize MACCFG2. */
-	tempval = MACCFG2_INIT_SETTINGS;
+	tempval = gfar_read(&regs->maccfg2);
+	tempval |= MACCFG2_PAD_CRC;

 	/* eTSEC74 erratum: Rx frames of length MAXFRM or MAXFRM-1
 	 * are marked as truncated.  Avoid this by MACCFG2[Huge Frame]=1,
diff --git a/drivers/net/ethernet/freescale/gianfar.h b/drivers/net/ethernet/freescale/gianfar.h
index f472a6d..cc70e03 100644
--- a/drivers/net/ethernet/freescale/gianfar.h
+++ b/drivers/net/ethernet/freescale/gianfar.h
@@ -150,8 +150,8 @@ extern const char gfar_driver_version[];
 #define MACCFG1_SYNCD_TX_EN	0x00000002
 #define MACCFG1_TX_EN		0x00000001

-#define MACCFG2_INIT_SETTINGS	0x00007205
 #define MACCFG2_FULL_DUPLEX	0x00000001
+#define MACCFG2_PAD_CRC         0x00000004
 #define MACCFG2_IF              0x00000300
 #define MACCFG2_MII             0x00000100
 #define MACCFG2_GMII            0x00000200
-- 
2.7.4