Re: [PATCH] e1000e: move force SMBUS near the end of enable_ulp function

["Lifshits, Vitaly" <vitaly.lifshits@intel.com>]

On 4/13/2024 12:27 PM, Hui Wang wrote:
> The commit 861e8086029e ("e1000e: move force SMBUS from enable ulp
> function to avoid PHY loss issue") introduces a regression on
> CH_MTP_I219_LM18 (PCIID: 0x8086550A). Without this commit, the
> ethernet works well after suspend and resume, but after applying the
> commit, the ethernet couldn't work anymore after the resume and the
> dmesg shows that the NIC Link changes to 10Mbps (1000Mbps originally):
> [   43.305084] e1000e 0000:00:1f.6 enp0s31f6: NIC Link is Up 10 Mbps Full Duplex, Flow Control: Rx/Tx
> 
> Without the commit, the force SMBUS code will not be executed if
> "return 0" or "goto out" is executed in the enable_ulp(), and in my
> case, the "goto out" is executed since FWSM_FW_VALID is set. But after
> applying the commit, the force SMBUS code will be ran unconditionally.
> 
> Here move the force SMBUS code back to enable_ulp() and put it
> immediate ahead of hw->phy.ops.release(hw), this could allow the
> longest settling time as possible for interface in this function and
> doesn't change the original code logic.
> 
> Fixes: 861e8086029e ("e1000e: move force SMBUS from enable ulp function to avoid PHY loss issue")
> Signed-off-by: Hui Wang <hui.wang@canonical.com>
> ---
>   drivers/net/ethernet/intel/e1000e/ich8lan.c | 19 +++++++++++++++++++
>   drivers/net/ethernet/intel/e1000e/netdev.c  | 18 ------------------
>   2 files changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
> index f9e94be36e97..dd670cd87df2 100644
> --- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
> +++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
> @@ -1225,6 +1225,25 @@ s32 e1000_enable_ulp_lpt_lp(struct e1000_hw *hw, bool to_sx)
>   	}
>   
>   release:
> +	/* Switching PHY interface always returns MDI error
> +	 * so disable retry mechanism to avoid wasting time
> +	 */
> +	e1000e_disable_phy_retry(hw);
> +
> +	/* Force SMBus mode in PHY */
> +	ret_val = e1000_read_phy_reg_hv_locked(hw, CV_SMB_CTRL, &phy_reg);
> +	if (ret_val)
> +		goto release;
> +	phy_reg |= CV_SMB_CTRL_FORCE_SMBUS;
> +	e1000_write_phy_reg_hv_locked(hw, CV_SMB_CTRL, phy_reg);
> +
> +	e1000e_enable_phy_retry(hw);
> +
> +	/* Force SMBus mode in MAC */
> +	mac_reg = er32(CTRL_EXT);
> +	mac_reg |= E1000_CTRL_EXT_FORCE_SMBUS;
> +	ew32(CTRL_EXT, mac_reg);
> +
>   	hw->phy.ops.release(hw);
>   out:
>   	if (ret_val)
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index 3692fce20195..cc8c531ec3df 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -6623,7 +6623,6 @@ static int __e1000_shutdown(struct pci_dev *pdev, bool runtime)
>   	struct e1000_hw *hw = &adapter->hw;
>   	u32 ctrl, ctrl_ext, rctl, status, wufc;
>   	int retval = 0;
> -	u16 smb_ctrl;
>   
>   	/* Runtime suspend should only enable wakeup for link changes */
>   	if (runtime)
> @@ -6697,23 +6696,6 @@ static int __e1000_shutdown(struct pci_dev *pdev, bool runtime)
>   			if (retval)
>   				return retval;
>   		}
> -
> -		/* Force SMBUS to allow WOL */
> -		/* Switching PHY interface always returns MDI error
> -		 * so disable retry mechanism to avoid wasting time
> -		 */
> -		e1000e_disable_phy_retry(hw);
> -
> -		e1e_rphy(hw, CV_SMB_CTRL, &smb_ctrl);
> -		smb_ctrl |= CV_SMB_CTRL_FORCE_SMBUS;
> -		e1e_wphy(hw, CV_SMB_CTRL, smb_ctrl);
> -
> -		e1000e_enable_phy_retry(hw);
> -
> -		/* Force SMBus mode in MAC */
> -		ctrl_ext = er32(CTRL_EXT);
> -		ctrl_ext |= E1000_CTRL_EXT_FORCE_SMBUS;
> -		ew32(CTRL_EXT, ctrl_ext);
>   	}
>   
>   	/* Ensure that the appropriate bits are set in LPI_CTRL

Dear Hui,

Thank you for this patch and this observation.
I think that you found a real misbehaviour in the original patch.
However, I still think that forcing SMBUS functionality shouldn't be 
part of the ULP enabling flow, since they are two independent 
configurations.

I will soon submit a patch where I wrap forcing SMBUS in e1000_shutdown 
with an if that checks if the FWSM_FW_VALID bit it set.