[PATCH RFC net-next v2 1/7] net: stmmac: add BASE-X support to integrated PCS
Maxime Chevallier
maxime.chevallier at bootlin.com
Wed Mar 4 02:25:20 PST 2026
Hello Russell,
On 04/03/2026 09:48, Russell King (Oracle) wrote:
> The integrated PCS supports 802.3z (BASE-X) modes when the Synopsys
> IP is coupled with an appropriate SerDes to provide the electrical
> interface. The PCS presents a TBI interface to the SerDes for this.
> Thus, the BASE-X related registers are only present when TBI mode is
> supported.
>
> dwmac-qcom-ethqos added support for using 2.5G with the integrated PCS
> by calling dwmac_ctrl_ane() directly.
>
> Add support for the following to the integrated PCS:
> - 1000BASE-X protocol unconditionally.
> - 2500BASE-X if the coupled SerDes supports 2.5G speed.
> - The above without autonegotiation.
> - If the PCS supports TBI, then optional BASE-X autonegotiation for each
> of the above.
>
> Signed-off-by: Russell King (Oracle) <rmk+kernel at armlinux.org.uk>
Haven't tested ofc, but this patch looks good to me (well, my knowledge
about 1000BaseX vs SGMII w.r.t aneg mostly comes from you in the first
place).
Reviewed-by: Maxime Chevallier <maxime.chevallier at bootlin.com>
Maxime
> ---
> .../net/ethernet/stmicro/stmmac/stmmac_pcs.c | 96 ++++++++++++++++++-
> .../net/ethernet/stmicro/stmmac/stmmac_pcs.h | 1 +
> include/linux/stmmac.h | 1 +
> 3 files changed, 95 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
> index 88fa359ea716..e606dfb85f94 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
> @@ -16,6 +16,27 @@
> #define GMAC_ANE_LPA 0x0c /* ANE link partener ability */
> #define GMAC_TBI 0x14 /* TBI extend status */
>
> +static unsigned int dwmac_integrated_pcs_inband_caps(struct phylink_pcs *pcs,
> + phy_interface_t interface)
> +{
> + struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
> + unsigned int ib_caps;
> +
> + if (phy_interface_mode_is_8023z(interface)) {
> + ib_caps = LINK_INBAND_DISABLE;
> +
> + /* If the PCS supports TBI/RTBI, then BASE-X negotiation is
> + * supported.
> + */
> + if (spcs->support_tbi_rtbi)
> + ib_caps |= LINK_INBAND_ENABLE;
> +
> + return ib_caps;
> + }
> +
> + return 0;
> +}
> +
> static int dwmac_integrated_pcs_enable(struct phylink_pcs *pcs)
> {
> struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
> @@ -36,7 +57,39 @@ static void dwmac_integrated_pcs_get_state(struct phylink_pcs *pcs,
> unsigned int neg_mode,
> struct phylink_link_state *state)
> {
> - state->link = false;
> + struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
> + u32 status, lpa;
> +
> + status = readl(spcs->base + GMAC_AN_STATUS);
> +
> + if (phy_interface_mode_is_8023z(state->interface)) {
> + /* For BASE-X modes, the PCS block supports the advertisement
> + * and link partner advertisement registers using standard
> + * 802.3 format. The status register also has the link status
> + * and AN complete bits in the same bit location. This will
> + * only be used when AN is enabled.
> + */
> + lpa = readl(spcs->base + GMAC_ANE_LPA);
> +
> + phylink_mii_c22_pcs_decode_state(state, neg_mode, status, lpa);
> + } else {
> + state->link = false;
> + }
> +}
> +
> +static int dwmac_integrated_pcs_config_aneg(struct stmmac_pcs *spcs,
> + phy_interface_t interface,
> + const unsigned long *advertising)
> +{
> + bool changed = false;
> + u32 adv;
> +
> + adv = phylink_mii_c22_pcs_encode_advertisement(interface, advertising);
> + if (readl(spcs->base + GMAC_ANE_ADV) != adv)
> + changed = true;
> + writel(adv, spcs->base + GMAC_ANE_ADV);
> +
> + return changed;
> }
>
> static int dwmac_integrated_pcs_config(struct phylink_pcs *pcs,
> @@ -46,13 +99,28 @@ static int dwmac_integrated_pcs_config(struct phylink_pcs *pcs,
> bool permit_pause_to_mac)
> {
> struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
> + bool changed = false, ane = true;
> +
> + /* Only configure the advertisement and allow AN in BASE-X mode if
> + * the core supports TBI/RTBI. AN will be filtered out by via phylink
> + * and the .pcs_inband_caps() method above.
> + */
> + if (phy_interface_mode_is_8023z(interface) &&
> + spcs->support_tbi_rtbi) {
> + ane = neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED;
> +
> + changed = dwmac_integrated_pcs_config_aneg(spcs, interface,
> + advertising);
> + }
>
> - dwmac_ctrl_ane(spcs->base, 0, 1, spcs->priv->hw->reverse_sgmii_enable);
> + dwmac_ctrl_ane(spcs->base, 0, ane,
> + spcs->priv->hw->reverse_sgmii_enable);
>
> - return 0;
> + return changed;
> }
>
> static const struct phylink_pcs_ops dwmac_integrated_pcs_ops = {
> + .pcs_inband_caps = dwmac_integrated_pcs_inband_caps,
> .pcs_enable = dwmac_integrated_pcs_enable,
> .pcs_disable = dwmac_integrated_pcs_disable,
> .pcs_get_state = dwmac_integrated_pcs_get_state,
> @@ -84,9 +152,18 @@ void stmmac_integrated_pcs_irq(struct stmmac_priv *priv, u32 status,
> int stmmac_integrated_pcs_get_phy_intf_sel(struct phylink_pcs *pcs,
> phy_interface_t interface)
> {
> + struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
> +
> if (interface == PHY_INTERFACE_MODE_SGMII)
> return PHY_INTF_SEL_SGMII;
>
> + if (phy_interface_mode_is_8023z(interface)) {
> + if (spcs->support_tbi_rtbi)
> + return PHY_INTF_SEL_TBI;
> + else
> + return PHY_INTF_SEL_SGMII;
> + }
> +
> return -EINVAL;
> }
>
> @@ -104,7 +181,20 @@ int stmmac_integrated_pcs_init(struct stmmac_priv *priv, unsigned int offset,
> spcs->int_mask = int_mask;
> spcs->pcs.ops = &dwmac_integrated_pcs_ops;
>
> + /* If the PCS supports extended status, then it supports BASE-X AN
> + * with a TBI interface to the SerDes. Otherwise, we can support
> + * BASE-X without AN using SGMII, which is required for qcom-ethqos.
> + */
> + if (readl(spcs->base + GMAC_AN_STATUS) & BMSR_ESTATEN)
> + spcs->support_tbi_rtbi = true;
> +
> __set_bit(PHY_INTERFACE_MODE_SGMII, spcs->pcs.supported_interfaces);
> + __set_bit(PHY_INTERFACE_MODE_1000BASEX, spcs->pcs.supported_interfaces);
> +
> + /* Only allow 2500BASE-X if the SerDes has support. */
> + if (priv->plat->flags & STMMAC_FLAG_SERDES_SUPPORTS_2500M)
> + __set_bit(PHY_INTERFACE_MODE_2500BASEX,
> + spcs->pcs.supported_interfaces);
>
> priv->integrated_pcs = spcs;
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
> index 23bbd4f10bf8..12ea87792fcb 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
> @@ -32,6 +32,7 @@ struct stmmac_pcs {
> void __iomem *base;
> u32 int_mask;
> struct phylink_pcs pcs;
> + bool support_tbi_rtbi;
> };
>
> static inline struct stmmac_pcs *
> diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> index 2fc169c7117e..3a99c4ef420c 100644
> --- a/include/linux/stmmac.h
> +++ b/include/linux/stmmac.h
> @@ -192,6 +192,7 @@ enum dwmac_core_type {
> #define STMMAC_FLAG_EN_TX_LPI_CLK_PHY_CAP BIT(12)
> #define STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY BIT(13)
> #define STMMAC_FLAG_KEEP_PREAMBLE_BEFORE_SFD BIT(14)
> +#define STMMAC_FLAG_SERDES_SUPPORTS_2500M BIT(15)
>
> struct mac_device_info;
>
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