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net: dsa: sja1105: enable internal pull-down for RX_DV/CRS_DV/RX_CTL and RX_ER

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Some boards do not have the RX_ER MII signal connected. Normally in such
situation, those pins would be grounded, but then again, some boards
left it electrically floating.

When sending traffic to those switch ports, one can see that the
N_SOFERR statistics counter is incrementing once per each packet. The
user manual states for this counter that it may count the number of
frames "that have the MII error input being asserted prior to or
up to the SOF delimiter byte". So the switch MAC is sampling an
electrically floating signal, and preventing proper traffic reception
because of that.

As a workaround, enable the internal weak pull-downs on the input pads
for the MII control signals. This way, a floating signal would be
internally tied to ground.

The logic levels of signals which _are_ externally driven should not be
bothered by this 40-50 KOhm internal resistor. So it is not an issue to
enable the internal pull-down unconditionally, irrespective of PHY
interface type (MII, RMII, RGMII, SGMII) and of board layout.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vladimir Oltean
2020-04-17 22:50:52 +03:00
committed by David S. Miller
parent 0fde6e3b55
commit 135e30180f
3 changed files with 54 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/dsa/sja1105/sja1105_spi.c
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@@ -443,6 +443,7 @@ static struct sja1105_regs sja1105et_regs = {
.rgu = 0x100440,
/* UM10944.pdf, Table 86, ACU Register overview */
.pad_mii_tx = {0x100800, 0x100802, 0x100804, 0x100806, 0x100808},
.pad_mii_rx = {0x100801, 0x100803, 0x100805, 0x100807, 0x100809},
.rmii_pll1 = 0x10000A,
.cgu_idiv = {0x10000B, 0x10000C, 0x10000D, 0x10000E, 0x10000F},
.mac = {0x200, 0x202, 0x204, 0x206, 0x208},
@@ -475,6 +476,7 @@ static struct sja1105_regs sja1105pqrs_regs = {
.rgu = 0x100440,
/* UM10944.pdf, Table 86, ACU Register overview */
.pad_mii_tx = {0x100800, 0x100802, 0x100804, 0x100806, 0x100808},
.pad_mii_rx = {0x100801, 0x100803, 0x100805, 0x100807, 0x100809},
.pad_mii_id = {0x100810, 0x100811, 0x100812, 0x100813, 0x100814},
.sgmii = 0x1F0000,
.rmii_pll1 = 0x10000A,