linux-kernel - Re: [RFC PATCH v2 5/8] net: pcs: add driver for MediaTek USXGMII PCS

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Message-ID: <20231206105838.069ae288@device.home>
Date:   Wed, 6 Dec 2023 10:58:38 +0100
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Alexander Couzens <lynxis@...0.eu>,
        Qingfang Deng <dqfext@...il.com>,
        SkyLake Huang <SkyLake.Huang@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-phy@...ts.infradead.org
Subject: Re: [RFC PATCH v2 5/8] net: pcs: add driver for MediaTek USXGMII
 PCS

Hello Daniel,

On Wed, 6 Dec 2023 01:44:38 +0000
Daniel Golle <daniel@...rotopia.org> wrote:

> Add driver for USXGMII PCS found in the MediaTek MT7988 SoC and supporting
> USXGMII, 10GBase-R and 5GBase-R interface modes. In order to support
> Cisco SGMII, 1000Base-X and 2500Base-X via the also present LynxI PCS
> create a wrapped PCS taking care of the components shared between the
> new USXGMII PCS and the legacy LynxI PCS.
> 
> Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> ---

[...]

> +
> +static int mtk_usxgmii_pcs_config(struct phylink_pcs *pcs, unsigned int neg_mode,
> +				  phy_interface_t interface,
> +				  const unsigned long *advertising,
> +				  bool permit_pause_to_mac)
> +{
> +	struct mtk_usxgmii_pcs *mpcs = pcs_to_mtk_usxgmii_pcs(pcs);
> +	unsigned int an_ctrl = 0, link_timer = 0, xfi_mode = 0, adapt_mode = 0;
> +	bool mode_changed = false;

Reverse christmas tree ordering can be used here (longest lines first)

> +
> +	if (interface == PHY_INTERFACE_MODE_USXGMII) {
> +		an_ctrl = FIELD_PREP(USXGMII_AN_SYNC_CNT, 0x1FF) | USXGMII_AN_ENABLE;
> +		link_timer = FIELD_PREP(USXGMII_LINK_TIMER_IDLE_DETECT, 0x7B) |
> +			     FIELD_PREP(USXGMII_LINK_TIMER_COMP_ACK_DETECT, 0x7B) |
> +			     FIELD_PREP(USXGMII_LINK_TIMER_AN_RESTART, 0x7B);
> +		xfi_mode = FIELD_PREP(USXGMII_XFI_RX_MODE, USXGMII_XFI_MODE_10G) |
> +			   FIELD_PREP(USXGMII_XFI_TX_MODE, USXGMII_XFI_MODE_10G);
> +	} else if (interface == PHY_INTERFACE_MODE_10GBASER) {
> +		an_ctrl = FIELD_PREP(USXGMII_AN_SYNC_CNT, 0x1FF);
> +		link_timer = FIELD_PREP(USXGMII_LINK_TIMER_IDLE_DETECT, 0x7B) |
> +			     FIELD_PREP(USXGMII_LINK_TIMER_COMP_ACK_DETECT, 0x7B) |
> +			     FIELD_PREP(USXGMII_LINK_TIMER_AN_RESTART, 0x7B);
> +		xfi_mode = FIELD_PREP(USXGMII_XFI_RX_MODE, USXGMII_XFI_MODE_10G) |
> +			   FIELD_PREP(USXGMII_XFI_TX_MODE, USXGMII_XFI_MODE_10G);
> +		adapt_mode = USXGMII_RATE_UPDATE_MODE;
> +	} else if (interface == PHY_INTERFACE_MODE_5GBASER) {
> +		an_ctrl = FIELD_PREP(USXGMII_AN_SYNC_CNT, 0xFF);
> +		link_timer = FIELD_PREP(USXGMII_LINK_TIMER_IDLE_DETECT, 0x3D) |
> +			     FIELD_PREP(USXGMII_LINK_TIMER_COMP_ACK_DETECT, 0x3D) |
> +			     FIELD_PREP(USXGMII_LINK_TIMER_AN_RESTART, 0x3D);
> +		xfi_mode = FIELD_PREP(USXGMII_XFI_RX_MODE, USXGMII_XFI_MODE_5G) |
> +			   FIELD_PREP(USXGMII_XFI_TX_MODE, USXGMII_XFI_MODE_5G);
> +		adapt_mode = USXGMII_RATE_UPDATE_MODE;
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	adapt_mode |= FIELD_PREP(USXGMII_RATE_ADAPT_MODE, USXGMII_RATE_ADAPT_MODE_X1);
> +
> +	if (mpcs->interface != interface) {
> +		mpcs->interface = interface;
> +		mode_changed = true;
> +	}
> +
> +	mtk_usxgmii_reset(mpcs);
> +
> +	/* Setup USXGMII AN ctrl */
> +	mtk_m32(mpcs, RG_PCS_AN_CTRL0,
> +		USXGMII_AN_SYNC_CNT | USXGMII_AN_ENABLE,
> +		an_ctrl);
> +
> +	mtk_m32(mpcs, RG_PCS_AN_CTRL2,
> +		USXGMII_LINK_TIMER_IDLE_DETECT |
> +		USXGMII_LINK_TIMER_COMP_ACK_DETECT |
> +		USXGMII_LINK_TIMER_AN_RESTART,
> +		link_timer);
> +
> +	mpcs->neg_mode = neg_mode;
> +
> +	/* Gated MAC CK */
> +	mtk_m32(mpcs, RG_PHY_TOP_SPEED_CTRL1,
> +		USXGMII_MAC_CK_GATED, USXGMII_MAC_CK_GATED);
> +
> +	/* Enable interface force mode */
> +	mtk_m32(mpcs, RG_PHY_TOP_SPEED_CTRL1,
> +		USXGMII_IF_FORCE_EN, USXGMII_IF_FORCE_EN);
> +
> +	/* Setup USXGMII adapt mode */
> +	mtk_m32(mpcs, RG_PHY_TOP_SPEED_CTRL1,
> +		USXGMII_RATE_UPDATE_MODE | USXGMII_RATE_ADAPT_MODE,
> +		adapt_mode);
> +
> +	/* Setup USXGMII speed */
> +	mtk_m32(mpcs, RG_PHY_TOP_SPEED_CTRL1,
> +		USXGMII_XFI_RX_MODE | USXGMII_XFI_TX_MODE,
> +		xfi_mode);
> +
> +	usleep_range(1, 10);
> +
> +	/* Un-gated MAC CK */
> +	mtk_m32(mpcs, RG_PHY_TOP_SPEED_CTRL1, USXGMII_MAC_CK_GATED, 0);
> +
> +	usleep_range(1, 10);
> +
> +	/* Disable interface force mode for the AN mode */
> +	if (an_ctrl & USXGMII_AN_ENABLE)
> +		mtk_m32(mpcs, RG_PHY_TOP_SPEED_CTRL1, USXGMII_IF_FORCE_EN, 0);
> +
> +	return mode_changed;
> +}
> +

[...]

> +static void mtk_usxgmii_pcs_get_state(struct phylink_pcs *pcs,
> +				      struct phylink_link_state *state)
> +{
> +	struct mtk_usxgmii_pcs *mpcs = pcs_to_mtk_usxgmii_pcs(pcs);
> +
> +	/* Refresh USXGMII link status by toggling RG_PCS_AN_STATUS_UPDATE */
> +	mtk_m32(mpcs, RG_PCS_RX_STATUS0, RG_PCS_RX_STATUS_UPDATE,
> +		RG_PCS_RX_STATUS_UPDATE);
> +	ndelay(1020);
> +	mtk_m32(mpcs, RG_PCS_RX_STATUS0, RG_PCS_RX_STATUS_UPDATE, 0);
> +	ndelay(1020);
> +
> +	/* Read USXGMII link status */
> +	state->link = FIELD_GET(RG_PCS_RX_LINK_STATUS,
> +				mtk_r32(mpcs, RG_PCS_RX_STATUS0));
> +
> +	/* Continuously repeat re-configuration sequence until link comes up */
> +	if (!state->link) {
> +		mtk_usxgmii_pcs_config(pcs, mpcs->neg_mode,
> +				       state->interface, NULL, false);
> +		return;

.pcs_get_state() isn't called only for link state polling,but also when querying
the link state from ethtool, from phylink_ethtool_ksettings_get().

As mtk_usxgmii_pcs_config triggers a pcs reset and reconfiguration, won't this disrupt
the link ? 

Thanks,

Maxime