Subject: [PATCH net-next 0/6] net: dsa: sja1105: phylink updates

From: "Russell King (Oracle)" <[email-masked]>
Date: Fri, 25 Feb 2022 11:55:42 +0000

Hi,

This series updates the phylink implementation in sja1105 to use the
supported_interfaces bitmap, convert to the mac_select_pcs() interface,
mark as non-legacy, and get rid of the validation method.

As a final step, enable switching between SGMII and 2500BASE-X as it
is a feature that Vladimir desires.

Specifically, the patches in this series:

1. Populates the supported_interfaces bitmap.
2. As a result of the supported_interfaces bitmap being populated,
   sja1105 no longer needs to check the interface mode as phylink
   will do this.
3. Switch away from using phylink_set_pcs(), using the mac_select_pcs()
   method instead.
4. Mark the driver as not-legacy
5. Fill in mac_capabilities using _exactly_ the same conditions as is
   currently used to decide which link modes to support, and convert
   to use phylink_generic_validate()
6. Add brand new support to permit switching between SGMII and
   2500BASE-X modes of operation as per Vladimir's single patch that
   performs steps 1, 2, 5 and 6 in one go.

There are some additional changes in Vladimir's single patch that I
have not included:

* validation of priv->phy_mode[] in sja1105_phylink_get_caps(). The
  driver has already validated the phy_mode for each port in
  sja1105_init_mii_settings(), and a failure here will prevent the
  driver reaching sja1105_phylink_get_caps().

* Changing the decisions on which mac_capabilities to set. Vladimir's
  patch always sets MAC_10FD | MAC_100FD | MAC_1000FD despite the
  current code clearly making the 1G speed conditional on the
  xmii_mode for the port. The change in decision making may be
  visible when in PHY_INTERFACE_MODE_INTERNAL mode, for which
  the phylink_generic_validate() will pass through all the MAC
  capabilities as ethtool link modes.

  Hence, if we have PHY_INTERFACE_MODE_INTERNAL but supports_rgmii[]
  or supports_sgmii[] is non-zero, currently we do not get 1G speeds.
  With Vladimir's additional change, we will get 1G speeds.

  While it is not clear whether that can happen, I feel changing the
  decision making should be a separate patch.

* The decision for MAC_2500FD is made differently -
  sja1105_init_mii_settings() allows PHY_INTERFACE_MODE_2500BASEX
  when supports_2500basex[] is non-zero, and is not based on any other
  condition such as supports_sgmii[] or supports_rgmii[]. Vladimir's
  patch makes it additionally conditional on those supports_.gmii[]
  settings, which is a functional change that should be made in a
  separate patch - and if desired, then sja1105_init_mii_settings()
  should also be updated at the same time.

Consequently, I believe that my previous objections to Vladimir's
single patch approach are well founded and justified, even through
Vladimir is the maintainer of this driver. I have no objection to
the additional changes, I just don't think they should all be wrapped
up into a single patch that converts the way validation is done _and_
also makes a bunch of other functional changes.

RFC->non-RFC: added Vladimir's Reviewed-by's, fixed the typo in the
commit message of patch 6, and removed the phrase at the end of a
comment as requested.

 drivers/net/dsa/sja1105/sja1105_main.c | 100 ++++++++++++++-------------------
 1 file changed, 42 insertions(+), 58 deletions(-)

-- 
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