On Wed, 2021-10-13 at 10:18 +0000, Philippe Schenker wrote:

On Wed, 2021-10-13 at 10:46 +0200, Matthias Schiffer wrote:

quoted

On Wed, 2021-10-13 at 08:25 +0000, Philippe Schenker wrote:

quoted

On Tue, 2021-10-12 at 12:34 +0200, Matthias Schiffer wrote:

quoted

It seems reasonable to fine-tune only some of the skew values when
using
one of the rgmii-*id PHY modes, and even when all skew values are
specified, using the correct ID PHY mode makes sense for
documentation
purposes. Such a configuration also appears in the binding docs in
Documentation/devicetree/bindings/net/micrel-ksz90x1.txt, so the
driver
should not warn about it.

I don't think your commit message is right. The rgmii-*id PHY modes
are
no longer just for documentation purposes on KSZ9031 PHY. They are
used
to set the skew-registers according to .

Yes, this was implemented in [1]. The commit message explicitly states
that fine-tuning is still possible using *-skew-ps.

quoted

The warning is there, that in case you override the skew registers
of
one of the modes rgmii-id, rgmii-txid, rgmii-rxid with *-skew-ps
settings in DT.

The "rgmii" mode should not be handled differently from "rgmii-*id" in
my opinion. Otherwise for a device that is basically "rgmii-id", but
requires slight fine-tuning, you have to set the mode to the incorrect
value "rgmii" in the DTS to avoid this warning.

Now I have understood your argument. But then I suggest to delete the
warning entirely as it completely changes its meaning with that patch.

Philippe

The KSZ9031 also supports MII and GMII though. I think it makes sense
to keep the warning for these cases (which is why I reworded the
warning the way I did).

quoted

quoted

Therefore I also think the warning is valuable and should be kept.
We
may want to reword it though.

Philippe

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/net/phy/micrel.c?id=bcf3440c6dd78bfe5836ec0990fe36d7b4bb7d20

quoted

quoted

Signed-off-by: Matthias Schiffer
[off-list ref]
---
 drivers/net/phy/micrel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index c330a5a9f665..03e58ebf68af 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c

@@ -863,9 +863,9 @@ static int ksz9031_config_init(struct

phy_device
*phydev)
                                MII_KSZ9031RN_TX_DATA_PAD_SKEW, 4,
                                tx_data_skews, 4, &update);
 
-               if (update && phydev->interface !=
PHY_INTERFACE_MODE_RGMII)
+               if (update && !phy_interface_is_rgmii(phydev))
                        phydev_warn(phydev,
-                                   "*-skew-ps values should be
used
only with phy-mode = \"rgmii\"\n");
+                                   "*-skew-ps values should be
used
only with RGMII PHY modes\n");
 
                /* Silicon Errata Sheet (DS80000691D or
DS80000692D):
                 * When the device links in the 1000BASE-T slave
mode
only,