From 66ef5adb75446627f8b6c26cd04f2adc86d4de56 Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Sat, 5 Sep 2026 15:02:32 +0200 Subject: [PATCH] net: ks8851: Fix receiver error in 100BASE-TX mode following software power-down KSZ8851 errata sheet DS80000716D-page 4 Module 3 [1] states that, when issuing a software power-down (PMECR[1:0] = 10) followed by a power-on (PMECR[1:0] = 00), the receiver circuit can fail to start properly preventing communication. The Transmitter will still send data, but no data will be received. The errata sheet also includes a workaround, which states that, it is recommended that the software power-down feature not be used. Implement that workaround and drop the entry into software power-down mode. The ks8851_write_mac_addr() calls entry into normal power-on mode at the very beginning of the function, therefore dropping the second call to enter software power-down mode is sufficient here. The ks8851_net_stop() can only be called after ks8851_net_start() was already called, and ks8851_net_start() also makes the MAC enter normal power-on mode, therefore it is also fine to drop the call to enter software power-down mode from ks8851_net_stop(). This will lead to a slight increase in power consumption, but it also fixes a sporadic reliability problem on at least KSZ8851-16MLL, which is where the problem was reported and this fix was tested. [1] https://ww1.microchip.com/downloads/en/DeviceDoc/80000716D.pdf Fixes: 3ba81f3ece3c ("net: Micrel KS8851 SPI network driver") Reviewed-by: Sebastian Andrzej Siewior Signed-off-by: Marek Vasut Link: https://patch.msgid.link/20260905130327.203851-1-marex@nabladev.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/micrel/ks8851_common.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/drivers/net/ethernet/micrel/ks8851_common.c b/drivers/net/ethernet/micrel/ks8851_common.c index 4afbb40bc0e4..d49f281c7867 100644 --- a/drivers/net/ethernet/micrel/ks8851_common.c +++ b/drivers/net/ethernet/micrel/ks8851_common.c @@ -143,9 +143,6 @@ static int ks8851_write_mac_addr(struct net_device *dev) ks8851_wrreg16(ks, KS_MAR(i), val); } - if (!netif_running(dev)) - ks8851_set_powermode(ks, PMECR_PM_SOFTDOWN); - ks8851_unlock(ks); return 0; @@ -478,8 +475,7 @@ static int ks8851_net_open(struct net_device *dev) * @dev: The device being closed. * * Called to close down a network device which has been active. Cancel any - * work, shutdown the RX and TX process and then place the chip into a low - * power state whilst it is not being used. + * work and shutdown the RX and TX process. */ static int ks8851_net_stop(struct net_device *dev) { @@ -506,8 +502,6 @@ static int ks8851_net_stop(struct net_device *dev) /* shutdown TX process */ ks8851_wrreg16(ks, KS_TXCR, 0x0000); - /* set powermode to soft power down to save power */ - ks8851_set_powermode(ks, PMECR_PM_SOFTDOWN); ks8851_unlock(ks); /* ensure any queued tx buffers are dumped */