linux-kernel - Re: [PATCH v2] net: ethernet: ti: am65-cpsw-qos: Add Frame Preemption MAC Merge support

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Date:   Fri, 11 Aug 2023 18:32:42 +0300
From:   Roger Quadros <rogerq@...nel.org>
To:     Simon Horman <horms@...nel.org>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, vladimir.oltean@....com, s-vadapalli@...com,
        srk@...com, vigneshr@...com, p-varis@...com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: ethernet: ti: am65-cpsw-qos: Add Frame Preemption
 MAC Merge support

Hi Simon,

On 11/08/2023 12:46, Simon Horman wrote:
> On Thu, Aug 10, 2023 at 06:25:38PM +0300, Roger Quadros wrote:
>> Add driver support for viewing / changing the MAC Merge sublayer
>> parameters and seeing the verification state machine's current state
>> via ethtool.
>>
>> As hardware does not support interrupt notification for verification
>> events we resort to polling on link up. On link up we try a couple of
>> times for verification success and if unsuccessful then give up.
>>
>> The Frame Preemption feature is described in the Technical Reference
>> Manual [1] in section:
>> 	12.3.1.4.6.7 Intersperced Express Traffic (IET – P802.3br/D2.0)
>>
>> Due to Silicon Errata i2208 [2] we set limit min IET fragment size to 124.
>>
>> [1] AM62x TRM - https://www.ti.com/lit/ug/spruiv7a/spruiv7a.pdf
>> [2] AM62x Silicon Errata - https://www.ti.com/lit/er/sprz487c/sprz487c.pdf
>>
>> Signed-off-by: Roger Quadros <rogerq@...nel.org>
> 
> Hi Roger,
> 
> some minor feedback from my side.
> 
> ...
> 
>> +static int am65_cpsw_get_mm(struct net_device *ndev, struct ethtool_mm_state *state)
>> +{
>> +	struct am65_cpsw_common *common = am65_ndev_to_common(ndev);
>> +	u32 port_ctrl, cmn_ctrl, iet_ctrl, iet_status, verify_cnt;
>> +	struct am65_cpsw_port *port = am65_ndev_to_port(ndev);
>> +	struct am65_cpsw_ndev_priv *priv = netdev_priv(ndev);
>> +	u32 add_frag_size;
>> +
>> +	mutex_lock(&priv->mm_lock);
>> +
>> +	iet_ctrl = readl(port->port_base + AM65_CPSW_PN_REG_IET_CTRL);
>> +	cmn_ctrl = readl(common->cpsw_base + AM65_CPSW_REG_CTL);
> 
> cmn_ctrl appears to be set but not used.
> Is this intentional?

No. It is stale code.
> 
>> +	port_ctrl = readl(port->port_base + AM65_CPSW_PN_REG_CTL);
>> +
>> +	state->tx_enabled = !!(iet_ctrl & AM65_CPSW_PN_IET_MAC_PENABLE);
>> +	state->pmac_enabled = !!(port_ctrl & AM65_CPSW_PN_CTL_IET_PORT_EN);
>> +
>> +	iet_status = readl(port->port_base + AM65_CPSW_PN_REG_IET_STATUS);
>> +
>> +	if (iet_ctrl & AM65_CPSW_PN_IET_MAC_DISABLEVERIFY)
>> +		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_DISABLED;
>> +	else if (iet_status & AM65_CPSW_PN_MAC_VERIFIED)
>> +		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_SUCCEEDED;
>> +	else if (iet_status & AM65_CPSW_PN_MAC_VERIFY_FAIL)
>> +		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_FAILED;
>> +	else
>> +		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_UNKNOWN;
>> +
>> +	add_frag_size = AM65_CPSW_PN_IET_MAC_GET_ADDFRAGSIZE(iet_ctrl);
>> +	state->tx_min_frag_size = ethtool_mm_frag_size_add_to_min(add_frag_size);
>> +
>> +	/* Errata i2208: RX min fragment size cannot be less than 124 */
>> +	state->rx_min_frag_size = 124;
>> +
>> +	/* FPE active if common tx_enabled and verification success or disabled (forced) */
>> +	state->tx_active = state->tx_enabled &&
>> +			   (state->verify_status == ETHTOOL_MM_VERIFY_STATUS_SUCCEEDED ||
>> +			    state->verify_status == ETHTOOL_MM_VERIFY_STATUS_DISABLED);
>> +	state->verify_enabled = !(iet_ctrl & AM65_CPSW_PN_IET_MAC_DISABLEVERIFY);
>> +
>> +	verify_cnt = AM65_CPSW_PN_MAC_GET_VERIFY_CNT(readl(port->port_base +
>> +							   AM65_CPSW_PN_REG_IET_VERIFY));
> 
> Likewise, verify_cnt appears to be set but not used.

Will remove it.
> 
>> +	state->verify_time = port->qos.iet.verify_time_ms;
>> +	state->max_verify_time = am65_cpsw_iet_get_verify_timeout_ms(AM65_CPSW_PN_MAC_VERIFY_CNT_MASK,
>> +								     port);
>> +	mutex_unlock(&priv->mm_lock);
>> +
>> +	return 0;
>> +}
> 
> ...
> 
>> +void am65_cpsw_iet_change_preemptible_tcs(struct am65_cpsw_port *port, u8 preemptible_tcs)
> 
> nit: should this function be static?
> 
>> +{
>> +	port->qos.iet.preemptible_tcs = preemptible_tcs;
>> +	am65_cpsw_iet_commit_preemptible_tcs(port);
>> +}
>> +
>> +void am65_cpsw_iet_link_state_update(struct net_device *ndev)
> 
> Ditto

Yes, both need to be static.
Thanks for review!

-- 
cheers,
-roger