Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Sat, 14 Dec 2019 12:28:37 -0800
From:   Jakub Kicinski <jakub.kicinski@netronome.com>
To:     Jose Abreu <Jose.Abreu@synopsys.com>
Cc:     netdev@vger.kernel.org, Joao Pinto <Joao.Pinto@synopsys.com>,
        Giuseppe Cavallaro <peppe.cavallaro@st.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        "David S. Miller" <davem@davemloft.net>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 4/4] net: stmmac: Always use TX coalesce timer
 value when rescheduling
Message-ID: <20191214122837.4960adfd@cakuba.netronome.com>
In-Reply-To: <23c0ff1feddcc690ee66adebefdc3b10031afe1b.1576007149.git.Jose.Abreu@synopsys.com>
References: <cover.1576007149.git.Jose.Abreu@synopsys.com>
        <23c0ff1feddcc690ee66adebefdc3b10031afe1b.1576007149.git.Jose.Abreu@synopsys.com>
Organization: Netronome Systems, Ltd.
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, 10 Dec 2019 20:54:44 +0100, Jose Abreu wrote:
> When we have pending packets we re-arm the TX timer with a magic value.
> Change this from the hardcoded value to the pre-defined TX coalesce
> timer value.

s/pre-defined/user controlled/ ?

> Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>
> ---
> Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
> Cc: Alexandre Torgue <alexandre.torgue@st.com>
> Cc: Jose Abreu <joabreu@synopsys.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> Cc: netdev@vger.kernel.org
> Cc: linux-stm32@st-md-mailman.stormreply.com
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index f61780ae30ac..726a17d9cc35 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1975,7 +1975,7 @@ static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
>  
>  	/* We still have pending packets, let's call for a new scheduling */
>  	if (tx_q->dirty_tx != tx_q->cur_tx)
> -		mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(10));
> +		mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(priv->tx_coal_timer));

I think intent of this code is to re-check the ring soon. The same
value of 10 is used in stmmac_tx_timer() for quick re-check.

tx_coal_timer defaults to 1000, so it's quite a jump from 10 to 1000.

I think the commit message leaves too much unsaid.

Also if you want to change to the ethtool timeout value, could you move 
stmmac_tx_timer_arm() and reuse that helper?

>  
>  	__netif_tx_unlock_bh(netdev_get_tx_queue(priv->dev, queue));
>