netdev - Re: [PATCH net-next v2 1/3] net: ethernet: ti: am65-cpsw: Move mode specific config to mac

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Date:   Mon, 3 Apr 2023 16:47:48 +0530
From:   Siddharth Vadapalli <s-vadapalli@...com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <rogerq@...nel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <srk@...com>,
        <s-vadapalli@...com>
Subject: Re: [PATCH net-next v2 1/3] net: ethernet: ti: am65-cpsw: Move mode
 specific config to mac_config()

Hello Russell,

Thank you for reviewing the patch.

On 03/04/23 16:38, Russell King (Oracle) wrote:
> On Mon, Apr 03, 2023 at 04:31:04PM +0530, Siddharth Vadapalli wrote:
>> Move the interface mode specific configuration to the mac_config()
>> callback am65_cpsw_nuss_mac_config().
>>
>> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
>> ---
>>  drivers/net/ethernet/ti/am65-cpsw-nuss.c | 10 +++++++---
>>  1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
>> index d17757ecbf42..74e099828978 100644
>> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
>> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
>> @@ -1504,12 +1504,17 @@ static void am65_cpsw_nuss_mac_config(struct phylink_config *config, unsigned in
>>  							  phylink_config);
>>  	struct am65_cpsw_port *port = container_of(slave, struct am65_cpsw_port, slave);
>>  	struct am65_cpsw_common *common = port->common;
>> +	u32 mac_control = 0;
>>  
>>  	if (common->pdata.extra_modes & BIT(state->interface)) {
>> -		if (state->interface == PHY_INTERFACE_MODE_SGMII)
>> +		if (state->interface == PHY_INTERFACE_MODE_SGMII) {
>> +			mac_control |= CPSW_SL_CTL_EXT_EN;
>>  			writel(ADVERTISE_SGMII,
>>  			       port->sgmii_base + AM65_CPSW_SGMII_MR_ADV_ABILITY_REG);
>> +		}
>>  
>> +		if (mac_control)
>> +			cpsw_sl_ctl_set(port->slave.mac_sl, mac_control);
>>  		writel(AM65_CPSW_SGMII_CONTROL_MR_AN_ENABLE,
>>  		       port->sgmii_base + AM65_CPSW_SGMII_CONTROL_REG);
>>  	}
>> @@ -1553,8 +1558,7 @@ static void am65_cpsw_nuss_mac_link_up(struct phylink_config *config, struct phy
>>  
>>  	if (speed == SPEED_1000)
>>  		mac_control |= CPSW_SL_CTL_GIG;
>> -	if (interface == PHY_INTERFACE_MODE_SGMII)
>> -		mac_control |= CPSW_SL_CTL_EXT_EN;
>> +	/* TODO: Verify whether in-band is necessary for 10 Mbps RGMII */
>>  	if (speed == SPEED_10 && phy_interface_mode_is_rgmii(interface))
>>  		/* Can be used with in band mode only */
>>  		mac_control |= CPSW_SL_CTL_EXT_EN;
> 
> I'm afraid I can see you haven't thought this patch through properly.
> 
> am65_cpsw_nuss_mac_link_down() will call
> cpsw_sl_ctl_reset(port->slave.mac_sl); which has the effect of clearing
> to zero the entire MAC control register. This will clear
> CPSW_SL_CTL_EXT_EN that was set in am65_cpsw_nuss_mac_config() which is
> not what you want to be doing.

Right! I missed noticing this. It appeared to me that simply moving the code
from mac_link_up() to mac_config() would suffice. However, as rightly pointed
out by you, it doesn't account for the case where the interface state is toggled.

> 
> Given that we have the 10Mbps issue with RGMII, I think what you want
> to be doing is:
> 
> 1. Set CPSW_SL_CTL_EXT_EN in am65_cpsw_nuss_mac_config() if in SGMII
>    mode, otherwise clear this bit.
> 
> 2. Clear the mac_control register in am65_cpsw_nuss_mac_link_down()
>    if in RMGII mode, otherwise preserve the state of
>    CPSW_SL_CTL_EXT_EN but clear all other bits.
> 
> 3. Set CPSW_SL_CTL_EXT_EN in am65_cpsw_nuss_mac_link_up() if in
>    RGMII mode and 10Mbps.
> 

I will implement these changes and post the v3 series. Thank you for the
feedback. Please let me know if I may add a "Suggested-by" tag.

Regards,
Siddharth.