sfc: handle limited FEC support

If the reported PHY capabilities do not include a given FEC mode, don't
 attempt to select that FEC mode anyway.  If the user tries to set a mode
 through ethtool that is not supported, return an error.
The _REQUESTED bits don't appear in the supported caps, but are implied
 by the corresponding FEC bits.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/sfc/mcdi_port_common.c

@@ -308,7 +308,7 @@ void efx_mcdi_phy_decode_link(struct efx_nic *efx,
  * Both RS and BASER (whether AUTO or not) means use FEC if cable and link
  * partner support it, preferring RS to BASER.
  */
-u32 ethtool_fec_caps_to_mcdi(u32 ethtool_cap)
+u32 ethtool_fec_caps_to_mcdi(u32 supported_cap, u32 ethtool_cap)
 {
 	u32 ret = 0;
 
@@ -316,17 +316,21 @@ u32 ethtool_fec_caps_to_mcdi(u32 ethtool_cap)
 		return 0;
 
 	if (ethtool_cap & ETHTOOL_FEC_AUTO)
-		ret |= (1 << MC_CMD_PHY_CAP_BASER_FEC_LBN) |
-		       (1 << MC_CMD_PHY_CAP_25G_BASER_FEC_LBN) |
-		       (1 << MC_CMD_PHY_CAP_RS_FEC_LBN);
-	if (ethtool_cap & ETHTOOL_FEC_RS)
+		ret |= ((1 << MC_CMD_PHY_CAP_BASER_FEC_LBN) |
+			(1 << MC_CMD_PHY_CAP_25G_BASER_FEC_LBN) |
+			(1 << MC_CMD_PHY_CAP_RS_FEC_LBN)) & supported_cap;
+	if (ethtool_cap & ETHTOOL_FEC_RS &&
+	    supported_cap & (1 << MC_CMD_PHY_CAP_RS_FEC_LBN))
 		ret |= (1 << MC_CMD_PHY_CAP_RS_FEC_LBN) |
 		       (1 << MC_CMD_PHY_CAP_RS_FEC_REQUESTED_LBN);
-	if (ethtool_cap & ETHTOOL_FEC_BASER)
-		ret |= (1 << MC_CMD_PHY_CAP_BASER_FEC_LBN) |
-		       (1 << MC_CMD_PHY_CAP_25G_BASER_FEC_LBN) |
-		       (1 << MC_CMD_PHY_CAP_BASER_FEC_REQUESTED_LBN) |
-		       (1 << MC_CMD_PHY_CAP_25G_BASER_FEC_REQUESTED_LBN);
+	if (ethtool_cap & ETHTOOL_FEC_BASER) {
+		if (supported_cap & (1 << MC_CMD_PHY_CAP_BASER_FEC_LBN))
+			ret |= (1 << MC_CMD_PHY_CAP_BASER_FEC_LBN) |
+			       (1 << MC_CMD_PHY_CAP_BASER_FEC_REQUESTED_LBN);
+		if (supported_cap & (1 << MC_CMD_PHY_CAP_25G_BASER_FEC_LBN))
+			ret |= (1 << MC_CMD_PHY_CAP_25G_BASER_FEC_LBN) |
+			       (1 << MC_CMD_PHY_CAP_25G_BASER_FEC_REQUESTED_LBN);
+	}
 	return ret;
 }
 
@@ -577,7 +581,7 @@ int efx_mcdi_phy_set_link_ksettings(struct efx_nic *efx, const struct ethtool_li
 		}
 	}
 
-	caps |= ethtool_fec_caps_to_mcdi(efx->fec_config);
+	caps |= ethtool_fec_caps_to_mcdi(phy_cfg->supported_cap, efx->fec_config);
 
 	rc = efx_mcdi_set_link(efx, caps, efx_get_mcdi_phy_flags(efx),
 			       efx->loopback_mode, 0);
@@ -645,12 +649,30 @@ int efx_mcdi_phy_get_fecparam(struct efx_nic *efx, struct ethtool_fecparam *fec)
 	return 0;
 }
 
+/* Basic validation to ensure that the caps we are going to attempt to set are
+ * in fact supported by the adapter.  Note that 'no FEC' is always supported.
+ */
+static int ethtool_fec_supported(u32 supported_cap, u32 ethtool_cap)
+{
+	if (ethtool_cap & ETHTOOL_FEC_OFF)
+		return 0;
+
+	if (ethtool_cap &&
+	    !ethtool_fec_caps_to_mcdi(supported_cap, ethtool_cap))
+		return -EINVAL;
+	return 0;
+}
+
 int efx_mcdi_phy_set_fecparam(struct efx_nic *efx, const struct ethtool_fecparam *fec)
 {
 	struct efx_mcdi_phy_data *phy_cfg = efx->phy_data;
 	u32 caps;
 	int rc;
 
+	rc = ethtool_fec_supported(phy_cfg->supported_cap, fec->fec);
+	if (rc)
+		return rc;
+
 	/* Work out what efx_mcdi_phy_set_link_ksettings() would produce from
 	 * saved advertising bits
 	 */
@@ -660,7 +682,7 @@ int efx_mcdi_phy_set_fecparam(struct efx_nic *efx, const struct ethtool_fecparam
 	else
 		caps = phy_cfg->forced_cap;
 
-	caps |= ethtool_fec_caps_to_mcdi(fec->fec);
+	caps |= ethtool_fec_caps_to_mcdi(phy_cfg->supported_cap, fec->fec);
 	rc = efx_mcdi_set_link(efx, caps, efx_get_mcdi_phy_flags(efx),
 			       efx->loopback_mode, 0);
 	if (rc)
@@ -699,7 +721,7 @@ int efx_mcdi_port_reconfigure(struct efx_nic *efx)
 		    ethtool_linkset_to_mcdi_cap(efx->link_advertising) :
 		    phy_cfg->forced_cap);
 
-	caps |= ethtool_fec_caps_to_mcdi(efx->fec_config);
+	caps |= ethtool_fec_caps_to_mcdi(phy_cfg->supported_cap, efx->fec_config);
 
 	return efx_mcdi_set_link(efx, caps, efx_get_mcdi_phy_flags(efx),
 				 efx->loopback_mode, 0);

drivers/net/ethernet/sfc/mcdi_port_common.h

@@ -41,7 +41,7 @@ u8 mcdi_to_ethtool_media(u32 media);
 void efx_mcdi_phy_decode_link(struct efx_nic *efx,
 			      struct efx_link_state *link_state,
 			      u32 speed, u32 flags, u32 fcntl);
-u32 ethtool_fec_caps_to_mcdi(u32 ethtool_cap);
+u32 ethtool_fec_caps_to_mcdi(u32 supported_cap, u32 ethtool_cap);
 u32 mcdi_fec_caps_to_ethtool(u32 caps, bool is_25g);
 void efx_mcdi_phy_check_fcntl(struct efx_nic *efx, u32 lpa);
 bool efx_mcdi_phy_poll(struct efx_nic *efx);