| Message ID | 20230425054429.3956535-2-s-vadapalli@ti.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | DP83867/DP83869 Ethernet PHY workaround/fix | expand |
On Tue, Apr 25, 2023 at 11:14:28AM +0530, 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. > > Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> > Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com> https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html Please set the tree in the Subject line to be net. Please also add a Fixes: tag, probably for the patch which added this driver. > --- > drivers/net/phy/dp83867.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c > index 5821f04c69dc..ba60cf35872e 100644 > --- a/drivers/net/phy/dp83867.c > +++ b/drivers/net/phy/dp83867.c > @@ -42,6 +42,7 @@ > #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 > @@ -934,8 +935,20 @@ 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; > + > + phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81); Maybe check the return code for errors? Andrew
On 25/04/23 17:35, Andrew Lunn wrote: > On Tue, Apr 25, 2023 at 11:14:28AM +0530, 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. >> >> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> >> Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com> > > https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html > > Please set the tree in the Subject line to be net. > Please also add a Fixes: tag, probably for the patch which added this driver. I will update the subject to "RFC PATCH net" and also add the "Fixes" tag in the v2 series. > > > > >> --- >> drivers/net/phy/dp83867.c | 15 ++++++++++++++- >> 1 file changed, 14 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c >> index 5821f04c69dc..ba60cf35872e 100644 >> --- a/drivers/net/phy/dp83867.c >> +++ b/drivers/net/phy/dp83867.c >> @@ -42,6 +42,7 @@ >> #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 >> @@ -934,8 +935,20 @@ 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; >> + >> + phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81); > > Maybe check the return code for errors? The return value of phy_write_mmd() doesn't have to be checked since it will be zero for the following reasons: The dp83867 driver does not have a custom .write_mmd method. Also, the dp83867 phy does not support clause 45. Due to this, within __phy_write_mmd(), the ELSE statement will be executed, which results in the return value being zero. > > Andrew
> >> @@ -934,8 +935,20 @@ 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; > >> + > >> + phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81); > > > > Maybe check the return code for errors? > > The return value of phy_write_mmd() doesn't have to be checked since it will be > zero for the following reasons: > The dp83867 driver does not have a custom .write_mmd method. Also, the dp83867 > phy does not support clause 45. Due to this, within __phy_write_mmd(), the ELSE > statement will be executed, which results in the return value being zero. Interesting. I would actually say __phy_write_mmd() is broken, and should be returning what __mdiobus_write() returns. You should assume it will get fixed, and check the return value. And it does no harm to check the return value. Andrew
On 26/04/23 18:06, Andrew Lunn wrote: >>>> @@ -934,8 +935,20 @@ 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; >>>> + >>>> + phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81); >>> >>> Maybe check the return code for errors? >> >> The return value of phy_write_mmd() doesn't have to be checked since it will be >> zero for the following reasons: >> The dp83867 driver does not have a custom .write_mmd method. Also, the dp83867 >> phy does not support clause 45. Due to this, within __phy_write_mmd(), the ELSE >> statement will be executed, which results in the return value being zero. > > Interesting. > > I would actually say __phy_write_mmd() is broken, and should be > returning what __mdiobus_write() returns. > > You should assume it will get fixed, and check the return value. And > it does no harm to check the return value. Thank you for clarifying. The reasoning behind the initial patch not checking the return value was: At all invocations of phy_write_mmd() in the dp83867 driver, at no place is the return value checked, which led me to analyze why that was the case. I noticed that it was due to the return value being guaranteed to be zero for this particular driver. Since the existing __phy_write_mmd() implementation is broken as pointed out by you, I will update this patch to check the return value. Also, I will probably add a cleanup patch as well, to fix this at all other invocations of phy_write_mmd() in the driver.
diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c index 5821f04c69dc..ba60cf35872e 100644 --- a/drivers/net/phy/dp83867.c +++ b/drivers/net/phy/dp83867.c @@ -42,6 +42,7 @@ #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 @@ -934,8 +935,20 @@ 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; + + phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_DSP_FFE_CFG, 0X0E81); + + 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)