From: Oleksij Rempel o.rempel@pengutronix.de
[ Upstream commit 6110dff776f7fa65c35850ef65b41d3b39e2fac2 ]
After the power-down bit is cleared, the chip internally triggers a global reset. According to the KSZ9031 documentation, we have to wait at least 1ms for the reset to finish.
If the chip is accessed during reset, read will return 0xffff, while write will be ignored. Depending on the system performance and MDIO bus speed, we may or may not run in to this issue.
This bug was discovered on an iMX6QP system with KSZ9031 PHY and attached PHY interrupt line. If IRQ was used, the link status update was lost. In polling mode, the link status update was always correct.
The investigation showed, that during a read-modify-write access, the read returned 0xffff (while the chip was still in reset) and corresponding write hit the chip _after_ reset and triggered (due to the 0xffff) another reset in an undocumented bit (register 0x1f, bit 1), resulting in the next write being lost due to the new reset cycle.
This patch fixes the issue by adding a 1...2 ms sleep after the genphy_resume().
Fixes: 836384d2501d ("net: phy: micrel: Add specific suspend") Signed-off-by: Oleksij Rempel o.rempel@pengutronix.de Reviewed-by: Andrew Lunn andrew@lunn.ch Reviewed-by: Florian Fainelli f.fainelli@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/phy/micrel.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/drivers/net/phy/micrel.c +++ b/drivers/net/phy/micrel.c @@ -29,6 +29,7 @@ #include <linux/micrel_phy.h> #include <linux/of.h> #include <linux/clk.h> +#include <linux/delay.h>
/* Operation Mode Strap Override */ #define MII_KSZPHY_OMSO 0x16 @@ -738,6 +739,12 @@ static int kszphy_resume(struct phy_devi
genphy_resume(phydev);
+ /* After switching from power-down to normal mode, an internal global + * reset is automatically generated. Wait a minimum of 1 ms before + * read/write access to the PHY registers. + */ + usleep_range(1000, 2000); + ret = kszphy_config_reset(phydev); if (ret) return ret;