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[2a01:c22:7655:7200:7d37:a922:8b7f:288b]) by smtp.googlemail.com with ESMTPSA id b16-20020a170906195000b0094e96e46cc0sm1055184eje.69.2023.05.09.01.59.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 May 2023 01:59:39 -0700 (PDT) Message-ID: <7a53f0d3-3e9a-4024-6b19-72ad9c19ab97@gmail.com> Date: Tue, 9 May 2023 10:59:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH net v2] net: phy: dp83867: add w/a for packet errors seen with short cables Content-Language: en-US To: Siddharth Vadapalli , andrew@lunn.ch, linux@armlinux.org.uk, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, srk@ti.com References: <20230509052124.611875-1-s-vadapalli@ti.com> From: Heiner Kallweit In-Reply-To: <20230509052124.611875-1-s-vadapalli@ti.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09.05.2023 07:21, Siddharth Vadapalli wrote: > From: Grygorii Strashko > > 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 > Signed-off-by: Siddharth Vadapalli > --- > > 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. > + 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)