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Date: Wed, 21 Feb 2024 09:31:56 +0000
From: "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>
To: Vladimir Oltean <vladimir.oltean@....com>, "netdev@...r.kernel.org"
<netdev@...r.kernel.org>
CC: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, Sean Anderson <sean.anderson@...o.com>, Russell King
<linux@...linux.org.uk>, Zachary Goldstein
<zachary.goldstein@...current-rt.com>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net] net: dpaa: fman_memac: accept phy-interface-type =
"10gbase-r" in the device tree
> -----Original Message-----
> From: Vladimir Oltean <vladimir.oltean@....com>
> Sent: Wednesday, February 21, 2024 12:35 AM
> To: netdev@...r.kernel.org
> Cc: David S. Miller <davem@...emloft.net>; Eric Dumazet
> <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
> <pabeni@...hat.com>; Madalin Bucur <madalin.bucur@....com>; Sean
> Anderson <sean.anderson@...o.com>; Russell King <linux@...linux.org.uk>;
> Zachary Goldstein <zachary.goldstein@...current-rt.com>; linux-
> kernel@...r.kernel.org
> Subject: [PATCH net] net: dpaa: fman_memac: accept phy-interface-type =
> "10gbase-r" in the device tree
>
> Since commit 5d93cfcf7360 ("net: dpaa: Convert to phylink"), we support
> the "10gbase-r" phy-mode through a driver-based conversion of "xgmii",
> but we still don't actually support it when the device tree specifies
> "10gbase-r" proper.
>
> This is because boards such as LS1046A-RDB do not define pcs-handle-names
> (for whatever reason) in the ethernet@...00 device tree node, and the
> code enters through this code path:
>
> err = of_property_match_string(mac_node, "pcs-handle-names", "xfi");
> // code takes neither branch and falls through
> if (err >= 0) {
> (...)
> } else if (err != -EINVAL && err != -ENODATA) {
> goto _return_fm_mac_free;
> }
>
> (...)
>
> /* For compatibility, if pcs-handle-names is missing, we assume this
> * phy is the first one in pcsphy-handle
> */
> err = of_property_match_string(mac_node, "pcs-handle-names",
> "sgmii");
> if (err == -EINVAL || err == -ENODATA)
> pcs = memac_pcs_create(mac_node, 0); // code takes this
> branch
> else if (err < 0)
> goto _return_fm_mac_free;
> else
> pcs = memac_pcs_create(mac_node, err);
>
> // A default PCS is created and saved in "pcs"
>
> // This determination fails and mistakenly saves the default PCS
> // memac->sgmii_pcs instead of memac->xfi_pcs, because at this
> // stage, mac_dev->phy_if == PHY_INTERFACE_MODE_10GBASER.
> if (err && mac_dev->phy_if == PHY_INTERFACE_MODE_XGMII)
> memac->xfi_pcs = pcs;
> else
> memac->sgmii_pcs = pcs;
>
> In other words, in the absence of pcs-handle-names, the default
> xfi_pcs assignment logic only works when in the device tree we have
> PHY_INTERFACE_MODE_XGMII.
>
> By reversing the order between the fallback xfi_pcs assignment and the
> "xgmii" overwrite with "10gbase-r", we are able to support both values
> in the device tree, with identical behavior.
>
> Currently, it is impossible to make the s/xgmii/10gbase-r/ device tree
> conversion, because it would break forward compatibility (new device
> tree with old kernel). The only way to modify existing device trees to
> phy-interface-mode = "10gbase-r" is to fix stable kernels to accept this
> value and handle it properly.
>
> One reason why the conversion is desirable is because with pre-phylink
> kernels, the Aquantia PHY driver used to warn about the improper use
> of PHY_INTERFACE_MODE_XGMII [1]. It is best to have a single (latest)
> device tree that works with all supported stable kernel versions.
>
> Note that the blamed commit does not constitute a regression per se.
> Older stable kernels like 6.1 still do not work with "10gbase-r", but
> for a different reason. That is a battle for another time.
>
> [1] https://lore.kernel.org/netdev/20240214-ls1046-dts-use-10gbase-r-v1-1-
> 8c2d68547393@...current-rt.com/
>
> Fixes: 5d93cfcf7360 ("net: dpaa: Convert to phylink")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
> .../net/ethernet/freescale/fman/fman_memac.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fman/fman_memac.c
> b/drivers/net/ethernet/freescale/fman/fman_memac.c
> index e30bf75b1d48..0996759907a8 100644
> --- a/drivers/net/ethernet/freescale/fman/fman_memac.c
> +++ b/drivers/net/ethernet/freescale/fman/fman_memac.c
> @@ -1076,6 +1076,14 @@ int memac_initialization(struct mac_device
> *mac_dev,
> unsigned long capabilities;
> unsigned long *supported;
>
> + /* The internal connection to the serdes is XGMII, but this isn't
> + * really correct for the phy mode (which is the external connection).
> + * However, this is how all older device trees say that they want
> + * 10GBASE-R (aka XFI), so just convert it for them.
> + */
> + if (mac_dev->phy_if == PHY_INTERFACE_MODE_XGMII)
> + mac_dev->phy_if = PHY_INTERFACE_MODE_10GBASER;
> +
> mac_dev->phylink_ops = &memac_mac_ops;
> mac_dev->set_promisc = memac_set_promiscuous;
> mac_dev->change_addr = memac_modify_mac_address;
> @@ -1142,7 +1150,7 @@ int memac_initialization(struct mac_device *mac_dev,
> * (and therefore that xfi_pcs cannot be set). If we are defaulting to
> * XGMII, assume this is for XFI. Otherwise, assume it is for SGMII.
> */
> - if (err && mac_dev->phy_if == PHY_INTERFACE_MODE_XGMII)
> + if (err && mac_dev->phy_if == PHY_INTERFACE_MODE_10GBASER)
> memac->xfi_pcs = pcs;
> else
> memac->sgmii_pcs = pcs;
> @@ -1156,14 +1164,6 @@ int memac_initialization(struct mac_device
> *mac_dev,
> goto _return_fm_mac_free;
> }
>
> - /* The internal connection to the serdes is XGMII, but this isn't
> - * really correct for the phy mode (which is the external connection).
> - * However, this is how all older device trees say that they want
> - * 10GBASE-R (aka XFI), so just convert it for them.
> - */
> - if (mac_dev->phy_if == PHY_INTERFACE_MODE_XGMII)
> - mac_dev->phy_if = PHY_INTERFACE_MODE_10GBASER;
> -
> /* TODO: The following interface modes are supported by (some)
> hardware
> * but not by this driver:
> * - 1000BASE-KX
> --
> 2.34.1
Thank you for the detailed description of the situation.
Acked-by: Madalin Bucur <madalin.bucur@....nxp.com>
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