36 lines
1.3 KiB
Diff
36 lines
1.3 KiB
Diff
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From: Russell King <rmk+kernel@armlinux.org.uk>
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Date: Thu, 5 Jan 2017 00:23:40 +0000
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Subject: [PATCH] net: phy: don't double-read clause 45 status register
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One of the design decisions behind the link status bit in the status
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register is that it latches low on link loss. This is so that link loss
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events are not missed. Double-reading the status register means that we
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always read the current state of the link, clearing any link loss event.
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This can cause problems - for example, if the link has negotiated a
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different set of operating parameters, these will not be communicated
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to the MAC as the PHY state machine will still think that the link has
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remained active.
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Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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---
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--- a/drivers/net/phy/phy-c45.c
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+++ b/drivers/net/phy/phy-c45.c
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@@ -143,12 +143,9 @@ int genphy_c45_read_link(struct phy_devi
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devad = __ffs(mmd_mask);
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mmd_mask &= ~BIT(devad);
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- val = phy_read_mmd(phydev, devad, MDIO_STAT1);
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- if (val < 0)
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- return val;
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-
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- /* Read twice because link state is latched and a
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- * read moves the current state into the register
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+ /* The link state is latched low so that momentary link
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+ * drops can be detected. Do not double-read the status
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+ * register if the link is down.
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*/
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val = phy_read_mmd(phydev, devad, MDIO_STAT1);
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if (val < 0)
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