Re: [PATCH] igb: conditionalize I2C bit banging on external thermal sensor support

[Leon Romanovsky <leon@kernel.org>]

On Wed, Dec 07, 2022 at 11:49:07AM +0100, Corinna Vinschen wrote:
> Commit a97f8783a937 ("igb: unbreak I2C bit-banging on i350") introduced
> code to change I2C settings to bit banging unconditionally.
> 
> However, this patch introduced a regression:  On an Intel S2600CWR
> Server Board with three NICs:
> 
> - 1x dual-port copper
>   Intel I350 Gigabit Network Connection [8086:1521] (rev 01)
>   fw 1.63, 0x80000dda
> 
> - 2x quad-port SFP+ with copper SFP Avago ABCU-5700RZ
>   Intel I350 Gigabit Fiber Network Connection [8086:1522] (rev 01)
>   fw 1.52.0
> 
> the SFP NICs no longer get link at all.  Reverting commit a97f8783a937
> or switching to the Intel out-of-tree driver both fix the problem.
> 
> Per the igb out-of-tree driver, I2C bit banging on i350 depends on
> support for an external thermal sensor (ETS).  However, commit
> a97f8783a937 added bit banging unconditionally.  Additionally, the
> out-of-tree driver always calls init_thermal_sensor_thresh on probe,
> while our driver only calls init_thermal_sensor_thresh only in
> igb_reset(), and only if an ETS is present, ignoring the internal
> thermal sensor.  The affected SFPs don't provide an ETS.  Per Intel,
> the behaviour is a result of i350 firmware requirements.
> 
> This patch fixes the problem by aligning the behaviour to the
> out-of-tree driver:
> 
> - split igb_init_i2c() into two functions:
>   - igb_init_i2c() only performs the basic I2C initialization.
>   - igb_set_i2c_bb() makes sure that E1000_CTRL_I2C_ENA is set
>     and enables bit-banging.
> 
> - igb_probe() only calls igb_set_i2c_bb() if an ETS is present.
> 
> - igb_probe() calls init_thermal_sensor_thresh() unconditionally.
> 
> - igb_reset() aligns its behaviour to igb_probe(), i. e., call
>   igb_set_i2c_bb() if an ETS is present and call
>   init_thermal_sensor_thresh() unconditionally.
> 
> Fixes: a97f8783a937 ("igb: unbreak I2C bit-banging on i350")
> Co-authored-by: Jamie Bainbridge <jbainbri@redhat.com>
> Tested-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
> Signed-off-by: Corinna Vinschen <vinschen@redhat.com>
> Signed-off-by: Jamie Bainbridge <jbainbri@redhat.com>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 44 +++++++++++++++++------
>  1 file changed, 34 insertions(+), 10 deletions(-)

The patch should have target in its title: "[PATCH net] ...."

> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 4e65ffe3f4e3..7f56322b3ec2 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -138,6 +138,9 @@ static irqreturn_t igb_msix_ring(int irq, void *);
>  static void igb_update_dca(struct igb_q_vector *);
>  static void igb_setup_dca(struct igb_adapter *);
>  #endif /* CONFIG_IGB_DCA */
> +#ifdef CONFIG_IGB_HWMON
> +static void igb_set_i2c_bb(struct e1000_hw *);

IMHO, it is better to follow kernel coding style for new code.
The functions should have variable names too.

> +#endif /* CONFIG_IGB_HWMON */
>  static int igb_poll(struct napi_struct *, int);
>  static bool igb_clean_tx_irq(struct igb_q_vector *, int);
>  static int igb_clean_rx_irq(struct igb_q_vector *, int);
> @@ -2399,7 +2402,8 @@ void igb_reset(struct igb_adapter *adapter)
>  			 * interface.
>  			 */
>  			if (adapter->ets)
> -				mac->ops.init_thermal_sensor_thresh(hw);
> +				igb_set_i2c_bb(hw);
> +			mac->ops.init_thermal_sensor_thresh(hw);
>  		}
>  	}
>  #endif
> @@ -3116,21 +3120,12 @@ static void igb_init_mas(struct igb_adapter *adapter)
>   **/
>  static s32 igb_init_i2c(struct igb_adapter *adapter)
>  {
> -	struct e1000_hw *hw = &adapter->hw;
>  	s32 status = 0;
> -	s32 i2cctl;
>  
>  	/* I2C interface supported on i350 devices */
>  	if (adapter->hw.mac.type != e1000_i350)
>  		return 0;
>  
> -	i2cctl = rd32(E1000_I2CPARAMS);
> -	i2cctl |= E1000_I2CBB_EN
> -		| E1000_I2C_CLK_OUT | E1000_I2C_CLK_OE_N
> -		| E1000_I2C_DATA_OUT | E1000_I2C_DATA_OE_N;
> -	wr32(E1000_I2CPARAMS, i2cctl);
> -	wrfl();
> -
>  	/* Initialize the i2c bus which is controlled by the registers.
>  	 * This bus will use the i2c_algo_bit structure that implements
>  	 * the protocol through toggling of the 4 bits in the register.
> @@ -3146,6 +3141,30 @@ static s32 igb_init_i2c(struct igb_adapter *adapter)
>  	return status;
>  }
>  
> +#ifdef CONFIG_IGB_HWMON
> +/**
> + *  igb_set_i2c_bb - Init I2C interface
> + *  @adapter: pointer to adapter structure
> + **/
> +static void igb_set_i2c_bb(struct e1000_hw *hw)
> +{
> +	s32 i2cctl;
> +	u32 ctrl_ext;

Reversed Christmas tree, please.

Thanks