MSCC_MS_SAM_FLOW_CTRL
vsc8584_macsec_phy_write(phydev, bank, MSCC_MS_SAM_FLOW_CTRL(idx), val);
val = vsc8584_macsec_phy_read(phydev, bank, MSCC_MS_SAM_FLOW_CTRL(idx));
vsc8584_macsec_phy_write(phydev, bank, MSCC_MS_SAM_FLOW_CTRL(idx), val);
val = vsc8584_macsec_phy_read(phydev, bank, MSCC_MS_SAM_FLOW_CTRL(idx));
vsc8584_macsec_phy_write(phydev, bank, MSCC_MS_SAM_FLOW_CTRL(idx), val);