Re: [RFC PATCH net-next v3 19/20] net: dsa: qca8k: pass switch_revision info to phy dev_flags

On Sat, May 08, 2021 at 12:33:53AM +0100, Russell King - ARM Linux admin wrote:

On Sat, May 08, 2021 at 01:26:02AM +0200, Ansuel Smith wrote:

quoted

On Thu, May 06, 2021 at 02:24:58PM +0300, Vladimir Oltean wrote:

quoted

On Wed, May 05, 2021 at 12:29:13AM +0200, Ansuel Smith wrote:

quoted

Define get_phy_flags to pass switch_Revision needed to tweak the
internal PHY with debug values based on the revision.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 drivers/net/dsa/qca8k.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index b4cd891ad35d..237e09bb1425 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c

@@ -1654,6 +1654,24 @@ qca8k_port_vlan_del(struct dsa_switch *ds, int port,
 	return ret;
 }
 
+static u32 qca8k_get_phy_flags(struct dsa_switch *ds, int port)
+{
+	struct qca8k_priv *priv = ds->priv;
+
+	pr_info("revision from phy %d", priv->switch_revision);

Log spam.

quoted

+	/* Communicate to the phy internal driver the switch revision.
+	 * Based on the switch revision different values needs to be
+	 * set to the dbg and mmd reg on the phy.
+	 * The first 2 bit are used to communicate the switch revision
+	 * to the phy driver.
+	 */
+	if (port > 0 && port < 6)
+		return priv->switch_revision;
+
+	return 0;
+}
+
 static enum dsa_tag_protocol
 qca8k_get_tag_protocol(struct dsa_switch *ds, int port,
 		       enum dsa_tag_protocol mp)

@@ -1687,6 +1705,7 @@ static const struct dsa_switch_ops qca8k_switch_ops = {
 	.phylink_mac_config	= qca8k_phylink_mac_config,
 	.phylink_mac_link_down	= qca8k_phylink_mac_link_down,
 	.phylink_mac_link_up	= qca8k_phylink_mac_link_up,
+	.get_phy_flags		= qca8k_get_phy_flags,
 };
 
 static int qca8k_read_switch_id(struct qca8k_priv *priv)

-- 
2.30.2

Florian, I think at one point you said that a correct user of
phydev->dev_flags should first check the PHY revision and not apply
dev_flags in blind, since they are namespaced to each PHY driver?
It sounds a bit circular to pass the PHY revision to the PHY through
phydev->dev_flags, either that or I'm missing some piece.

Just to make sure. This is the SWITCH revision not the PHY revision. It
was pointed out in old version that I should get this value from the PHY
regs but they are different values. This is why the dsa driver needs to
use the dev_flags to pass the SWITCH revision to the phy driver. Am I
implementing this in the wrong way and I should declare something to
pass this value in a more standard way? (anyway i'm pushing v4 so i
don't know if we should continue that there)

Vladimir is confused - it is not PHY revision at all, but the PHY
identifiers.

What was actually suggested was checking the PHY identifiers before
passing PHY-driver specific flags, so that we didn't end up setting
driver private flags that are intending for one driver, but end up
actually binding a different driver, and mis-interpreting the flags.

This is one of the problems of the current scheme: it's just a
meaningless opaque u32 variable with no defined structure to it that
the various PHY drivers themselves use in whatever way they see fit.
That is only fine to use _if_ you know for certain which driver is
going to bind ahead of time.

As I mentioned in direct reply to your patch, there was discussions
about this back in February, but they seem to have stalled.

Yes, I was indeed confused. My problem was mixing up the PHY OUI/device ID
and revision concepts in one big fuzzy notion. I remembered Heiner's
suggestion to do something similar to mv88e6xxx_mdio_read from here:
https://patchwork.kernel.org/project/netdevbpf/patch/20210423014741.11858-12-ansuelsmth@gmail.com/
(where the problem is that some internal PHYs are lacking a device
identifier) and thought that the problem here is the same.

Nonetheless, now it is clear to me that with care (don't set dev_flags
except for internal PHYs which are statically known), it is possible for
the PHY driver to have a larger identifier (PHY ID concatenated with
switch revision passed through dev_flags) based on which it can
configure the hardware.

Sorry.