linux-kernel - Re: [Intel-wired-lan] [PATCH net-next v2] drivers/net/ethernet: check return value of e1e

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Date:   Tue, 30 Aug 2022 00:05:45 -0700
From:   Li Zhong <floridsleeves@...il.com>
To:     "Neftin, Sasha" <sasha.neftin@...el.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, davem@...emloft.net,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "Ruinskiy, Dima" <dima.ruinskiy@...el.com>,
        "Fuxbrumer, Devora" <devora.fuxbrumer@...el.com>,
        "naamax.meir" <naamax.meir@...ux.intel.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH net-next v2] drivers/net/ethernet: check
 return value of e1e_rphy()

On Mon, Aug 29, 2022 at 11:03 AM Neftin, Sasha <sasha.neftin@...el.com> wrote:
>
> On 8/26/2022 09:56, Li Zhong wrote:
> > e1e_rphy() could return error value, which needs to be checked and
> > reported for debugging and diagnose.
> >
> > Signed-off-by: Li Zhong <floridsleeves@...il.com>
> > ---
> > drivers/net/ethernet/intel/e1000e/phy.c | 20 +++++++++++++++++---
> > 1 file changed, 17 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/e1000e/phy.c b/drivers/net/ethernet/intel/e1000e/phy.c
> > index fd07c3679bb1..060b263348ce 100644
> > --- a/drivers/net/ethernet/intel/e1000e/phy.c
> > +++ b/drivers/net/ethernet/intel/e1000e/phy.c
> > @@ -2697,9 +2697,14 @@ static s32 e1000_access_phy_wakeup_reg_bm(struct e1000_hw *hw, u32 offset,
> > void e1000_power_up_phy_copper(struct e1000_hw *hw)
> > {
> > u16 mii_reg = 0;
> > + int ret;
> >
> > /* The PHY will retain its settings across a power down/up cycle */
> > - e1e_rphy(hw, MII_BMCR, &mii_reg);
> > + ret = e1e_rphy(hw, MII_BMCR, &mii_reg);
> > + if (ret) {
> > + e_dbg("Error reading PHY register\n");
> > + return;
> > + }
> > mii_reg &= ~BMCR_PDOWN;
> > e1e_wphy(hw, MII_BMCR, mii_reg);
> > }
> > @@ -2715,9 +2720,14 @@ void e1000_power_up_phy_copper(struct e1000_hw *hw)
> > void e1000_power_down_phy_copper(struct e1000_hw *hw)
> > {
> > u16 mii_reg = 0;
> > + int ret;
> >
> > /* The PHY will retain its settings across a power down/up cycle */
> > - e1e_rphy(hw, MII_BMCR, &mii_reg);
> > + ret = e1e_rphy(hw, MII_BMCR, &mii_reg);
> > + if (ret) {
> > + e_dbg("Error reading PHY register\n");
> > + return;
> > + }
> > mii_reg |= BMCR_PDOWN;
> > e1e_wphy(hw, MII_BMCR, mii_reg);
> > usleep_range(1000, 2000);
> > @@ -3037,7 +3047,11 @@ s32 e1000_link_stall_workaround_hv(struct e1000_hw *hw)
> > return 0;
> >
> > /* Do not apply workaround if in PHY loopback bit 14 set */
> > - e1e_rphy(hw, MII_BMCR, &data);
> > + ret_val = e1e_rphy(hw, MII_BMCR, &data);
> > + if (ret_val) {
> > + e_dbg("Error reading PHY register\n");
> > + return ret_val;
> > + }
> > if (data & BMCR_LOOPBACK)
> > return 0;
> >
> Generally, I am good with this patch. One question - it is old HW, any
> idea how to check it? (82577/82578 GbE LOM - from 2008)
> Li, how did you check it manually?

These bugs are detected by static analysis. Therefore it's not run-time
checked. However, since currently there is no error handling after
e1e_rphy(), so I think it's necessary to at least check it and expect
there is a chance to fail.