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.
Signed-off-by: Grygorii Strashko <[email protected]>
Signed-off-by: Siddharth Vadapalli <[email protected]>
---
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);
+
+ 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
On Tue, Apr 25, 2023 at 11:14:28AM +0530, Siddharth Vadapalli wrote:
> 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.
>
> Signed-off-by: Grygorii Strashko <[email protected]>
> Signed-off-by: Siddharth Vadapalli <[email protected]>
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 <[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.
>>
>> Signed-off-by: Grygorii Strashko <[email protected]>
>> Signed-off-by: Siddharth Vadapalli <[email protected]>
>
> 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
--
Regards,
Siddharth.
> >> @@ -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.
--
Regards,
Siddharth.