2023-05-08 07:16:32

by Siddharth Vadapalli

Subject: [PATCH net] net: phy: dp83867: add w/a for packet errors seen with short cables

From: Grygorii Strashko <[email protected]>

Introduce the W/A for packet errors seen with short cables (<1m) between
two DP83867 PHYs.

The W/A recommended by DM requires FFE Equalizer Configuration tuning by
writing value 0x0E81 to DSP_FFE_CFG register (0x012C), surrounded by hard
and soft resets as follows:

write_reg(0x001F, 0x8000); //hard reset
write_reg(DSP_FFE_CFG, 0x0E81);
write_reg(0x001F, 0x4000); //soft reset

Since DP83867 PHY DM says "Changing this register to 0x0E81, will not
affect Long Cable performance.", enable the W/A by default.

Fixes: 2a10154abcb7 ("net: phy: dp83867: Add TI dp83867 phy")
Signed-off-by: Grygorii Strashko <[email protected]>
Signed-off-by: Siddharth Vadapalli <[email protected]>
---

RFC patch at:
https://lore.kernel.org/r/[email protected]/

Changes since RFC patch:
- Change patch subject to PATCH net.
- Add Fixes tag.
- Check return value of phy_write_mmd().

drivers/net/phy/dp83867.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c
index d75f526a20a4..4eecc9531a6b 100644
--- a/drivers/net/phy/dp83867.c
+++ b/drivers/net/phy/dp83867.c
@@ -44,6 +44,7 @@
#define DP83867_STRAP_STS1 0x006E
#define DP83867_STRAP_STS2 0x006f
#define DP83867_RGMIIDCTL 0x0086
+#define DP83867_DSP_FFE_CFG 0X012C
#define DP83867_RXFCFG 0x0134
#define DP83867_RXFPMD1 0x0136
#define DP83867_RXFPMD2 0x0137
@@ -941,8 +942,22 @@ static int dp83867_phy_reset(struct phy_device *phydev)

usleep_range(10, 20);

- return phy_modify(phydev, MII_DP83867_PHYCTRL,
+ err = phy_modify(phydev, MII_DP83867_PHYCTRL,
DP83867_PHYCR_FORCE_LINK_GOOD, 0);
+ if (err < 0)
+ return err;
+
+ err = phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81);
+ if (err < 0)
+ return err;
+
+ err = phy_write(phydev, DP83867_CTRL, DP83867_SW_RESTART);
+ if (err < 0)
+ return err;
+
+ usleep_range(10, 20);
+
+ return 0;
}

static void dp83867_link_change_notify(struct phy_device *phydev)
--
2.25.1

2023-05-09 02:17:11

by Jakub Kicinski

Subject: Re: [PATCH net] net: phy: dp83867: add w/a for packet errors seen with short cables

Thanks for the patch! Some nit picks below..

On Mon, 8 May 2023 12:30:19 +0530 Siddharth Vadapalli wrote:
> + err = phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81);

Pleas wrap this line at 80 characters, there's no reason for it
to be this long.

And 0x prefix should not be in upper case, here and in the new define
you're adding.
--
pw-bot: cr

2023-05-09 04:45:34

by Siddharth Vadapalli

Subject: Re: [PATCH net] net: phy: dp83867: add w/a for packet errors seen with short cables

On 09/05/23 07:30, Jakub Kicinski wrote:
> Thanks for the patch! Some nit picks below..
>
> On Mon, 8 May 2023 12:30:19 +0530 Siddharth Vadapalli wrote:
>> + err = phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81);
>
> Pleas wrap this line at 80 characters, there's no reason for it
> to be this long.
>
> And 0x prefix should not be in upper case, here and in the new define
> you're adding.

Thank you for pointing out the issues. I will fix them and post the v2 patch.

--
Regards,
Siddharth.