linux-kernel - Re: [PATCH net-next v7 6/7] net: stmmac: support fp parameter of tc-taprio

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Message-ID: <20240904155539.mh5crdw7xqudkjur@skbuf>
Date: Wed, 4 Sep 2024 18:55:39 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Furong Xu <0x1207@...il.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
	Serge Semin <fancer.lancer@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Joao Pinto <jpinto@...opsys.com>, netdev@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	rmk+kernel@...linux.org.uk, linux@...linux.org.uk, xfr@...look.com
Subject: Re: [PATCH net-next v7 6/7] net: stmmac: support fp parameter of
 tc-taprio

On Wed, Sep 04, 2024 at 05:21:21PM +0800, Furong Xu wrote:
>  .../net/ethernet/stmicro/stmmac/stmmac_tc.c   | 23 +++++++------------
>  1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> index 9ec2e6ab81aa..2bdb22e175bc 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> @@ -931,9 +931,9 @@ static int tc_taprio_configure(struct stmmac_priv *priv,
>  			       struct tc_taprio_qopt_offload *qopt)
>  {
>  	u32 size, wid = priv->dma_cap.estwid, dep = priv->dma_cap.estdep;
> +	struct netlink_ext_ack *extack = qopt->mqprio.extack;
>  	struct timespec64 time, current_time, qopt_time;
>  	ktime_t current_time_ns;
> -	bool fpe = false;
>  	int i, ret = 0;
>  	u64 ctr;
>  
> @@ -1018,16 +1018,12 @@ static int tc_taprio_configure(struct stmmac_priv *priv,
>  
>  		switch (qopt->entries[i].command) {
>  		case TC_TAPRIO_CMD_SET_GATES:
> -			if (fpe)
> -				return -EINVAL;
>  			break;
>  		case TC_TAPRIO_CMD_SET_AND_HOLD:
>  			gates |= BIT(0);
> -			fpe = true;
>  			break;
>  		case TC_TAPRIO_CMD_SET_AND_RELEASE:
>  			gates &= ~BIT(0);
> -			fpe = true;
>  			break;
>  		default:
>  			return -EOPNOTSUPP;
> @@ -1058,11 +1054,6 @@ static int tc_taprio_configure(struct stmmac_priv *priv,
>  
>  	tc_taprio_map_maxsdu_txq(priv, qopt);
>  
> -	if (fpe && !priv->dma_cap.fpesel) {
> -		mutex_unlock(&priv->est_lock);
> -		return -EOPNOTSUPP;
> -	}
> -
>  	ret = stmmac_est_configure(priv, priv, priv->est,
>  				   priv->plat->clk_ptp_rate);
>  	mutex_unlock(&priv->est_lock);
> @@ -1071,6 +1062,11 @@ static int tc_taprio_configure(struct stmmac_priv *priv,
>  		goto disable;
>  	}
>  
> +	ret = stmmac_fpe_map_preemption_class(priv, priv->dev, extack,
> +					      qopt->mqprio.preemptible_tcs);
> +	if (ret)
> +		goto disable;
> +

Doesn't this break taprio for those callers of tc_setup_taprio() which
do not implement fpe_map_preemption_class(), but at least want taprio
without FPE nonetheless? As in the earlier mqprio patch, they will
return -EINVAL here.

Through code inspection, those users are:
- All users of .tc = dwxgmac_tc_ops: they have .mac = &dwxlgmac2_ops or
  .mac = &dwxgmac210_ops, neither of which implements fpe_map_preemption_class().
- The users of .tc = &dwmac510_tc_ops which have .mac = &dwmac4_ops.
  Again, this does not implement .fpe_map_preemption_class().

I can only rely on code inspection, because I don't know what is the
priv->dma_cap.estsel value that the above cores were synthesized with.
Thus, I don't know if we break a feature which was available before, or
one that was already unavailable.

My suggestion is similar: allow mqprio.preemptible_tcs to go to non-zero
only if fpe_map_preemption_class() is implemented. Then, program it with
any value (including 0) only if fpe_map_preemption_class() is implemented.

>  	netdev_info(priv->dev, "configured EST\n");
>  
>  	return 0;