Messages in this thread | | | Date | Tue, 9 May 2023 12:40:37 +0200 | Subject | Re: [PATCH net v2] net: phy: dp83867: add w/a for packet errors seen with short cables | From | Heiner Kallweit <> |
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On 09.05.2023 12:27, Siddharth Vadapalli wrote: > > > On 09/05/23 14:29, Heiner Kallweit wrote: >> On 09.05.2023 07:21, Siddharth Vadapalli wrote: >>> From: Grygorii Strashko <grygorii.strashko@ti.com> >>> >>> 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 <grygorii.strashko@ti.com> >>> Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com> >>> --- >>> >>> V1 patch at: >>> https://lore.kernel.org/r/20230508070019.356548-1-s-vadapalli@ti.com >>> >>> Changes since v1 patch: >>> - Wrap the line invoking phy_write_mmd(), limiting it to 80 characters. >>> - Replace 0X0E81 with 0x0e81 in the call to phy_write_mmd(). >>> - Replace 0X012C with 0x012c in the new define for DP83867_DSP_FFE_CFG. >>> >>> RFC patch at: >>> https://lore.kernel.org/r/20230425054429.3956535-2-s-vadapalli@ti.com/ >>> >>> 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 | 18 +++++++++++++++++- >>> 1 file changed, 17 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c >>> index d75f526a20a4..bbdcc595715d 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 +942,23 @@ 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; >>> + >> >> Would be good to add a comment here explaining what this magic write does. > > Sure. Is the following comment acceptable? > > "Configure the DSP Feedforward Equalizer Configuration register to improve short > cable (< 1 meter) performance. This will not affect long cable performance." > Sounds good. Important is just that the magic value write is explained, so that readers of the source code don't have to scroll through the commit history.
>> >>> + 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) >> >
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