[PATCH net-next] net: phy: prefer 1000baseT over 1000baseKX

The PHY settings table is supposed to be sorted by descending match
priority - in other words, earlier entries are preferred over later
entries.

The order of 1000baseKX/Full and 1000baseT/Full is such that we
prefer 1000baseKX/Full over 1000baseT/Full, but 1000baseKX/Full is
a lot rarer than 1000baseT/Full, and thus is much less likely to
be preferred.

This causes phylink problems - it means a fixed link specifying a
speed of 1G and full duplex gets an ethtool linkmode of 1000baseKX/Full
rather than 1000baseT/Full as would be expected - and since we offer
userspace a software emulation of a conventional copper PHY, we want
to offer copper modes in preference to anything else. However, we do
still want to allow the rarer modes as well.

Hence, let's reorder these two modes to prefer copper.

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Russell King (Oracle) <redacted>
---
 drivers/net/phy/phy-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index 2870c33b8975..271fc01f7f7f 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c

@@ -162,11 +162,11 @@ static const struct phy_setting settings[] = {
 	PHY_SETTING(   2500, FULL,   2500baseT_Full		),
 	PHY_SETTING(   2500, FULL,   2500baseX_Full		),
 	/* 1G */
-	PHY_SETTING(   1000, FULL,   1000baseKX_Full		),
 	PHY_SETTING(   1000, FULL,   1000baseT_Full		),
 	PHY_SETTING(   1000, HALF,   1000baseT_Half		),
 	PHY_SETTING(   1000, FULL,   1000baseT1_Full		),
 	PHY_SETTING(   1000, FULL,   1000baseX_Full		),
+	PHY_SETTING(   1000, FULL,   1000baseKX_Full		),
 	/* 100M */
 	PHY_SETTING(    100, FULL,    100baseT_Full		),
 	PHY_SETTING(    100, FULL,    100baseT1_Full		),

-- 
2.30.2

On Wed, Dec 08, 2021 at 11:36:30AM +0000, Russell King (Oracle) wrote:

The PHY settings table is supposed to be sorted by descending match
priority - in other words, earlier entries are preferred over later
entries.

The order of 1000baseKX/Full and 1000baseT/Full is such that we
prefer 1000baseKX/Full over 1000baseT/Full, but 1000baseKX/Full is
a lot rarer than 1000baseT/Full, and thus is much less likely to
be preferred.

This causes phylink problems - it means a fixed link specifying a
speed of 1G and full duplex gets an ethtool linkmode of 1000baseKX/Full
rather than 1000baseT/Full as would be expected - and since we offer
userspace a software emulation of a conventional copper PHY, we want
to offer copper modes in preference to anything else. However, we do
still want to allow the rarer modes as well.

Hence, let's reorder these two modes to prefer copper.

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Russell King (Oracle) <redacted>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew

On 12/8/21 3:36 AM, Russell King (Oracle) wrote:

The PHY settings table is supposed to be sorted by descending match
priority - in other words, earlier entries are preferred over later
entries.

The order of 1000baseKX/Full and 1000baseT/Full is such that we
prefer 1000baseKX/Full over 1000baseT/Full, but 1000baseKX/Full is
a lot rarer than 1000baseT/Full, and thus is much less likely to
be preferred.

This causes phylink problems - it means a fixed link specifying a
speed of 1G and full duplex gets an ethtool linkmode of 1000baseKX/Full
rather than 1000baseT/Full as would be expected - and since we offer
userspace a software emulation of a conventional copper PHY, we want
to offer copper modes in preference to anything else. However, we do
still want to allow the rarer modes as well.

Hence, let's reorder these two modes to prefer copper.

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Russell King (Oracle) <redacted>

Reported-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski [off-list ref]:

On Wed, 08 Dec 2021 11:36:30 +0000 you wrote:

The PHY settings table is supposed to be sorted by descending match
priority - in other words, earlier entries are preferred over later
entries.

The order of 1000baseKX/Full and 1000baseT/Full is such that we
prefer 1000baseKX/Full over 1000baseT/Full, but 1000baseKX/Full is
a lot rarer than 1000baseT/Full, and thus is much less likely to
be preferred.

[...]

Here is the summary with links:
  - [net-next] net: phy: prefer 1000baseT over 1000baseKX
    https://git.kernel.org/netdev/net-next/c/f20f94f7f52c

You are awesome, thank you!
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