linux-kernel - Re: [PATCH net-next 03/10] net: mvneta: bm: add support for hardware buffer management

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Message-ID: <CAPv3WKeEXUmH4gqBm7=gkNYwjhR1YybCBZJND_Vidj+Q6U_8=g@mail.gmail.com>
Date:	Tue, 12 Jan 2016 21:12:25 +0100
From:	Marcin Wojtas <mw@...ihalf.com>
To:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Lior Amsalem <alior@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Simon Guinot <simon.guinot@...uanux.org>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Willy Tarreau <w@....eu>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH net-next 03/10] net: mvneta: bm: add support for hardware
 buffer management

Hi Gregory,

I have two remarks to my own code. Please let me know before patch v2,
I will provide you with corrected version (I already did it locally).

> @@ -1556,17 +1777,20 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp,
>         int rx_done, i;
>
>         rx_done = mvneta_rxq_busy_desc_num_get(pp, rxq);
> +       if (rx_done)
> +               mvneta_rxq_desc_num_update(pp, rxq, rx_done, rx_done);
> +
> +       if (pp->bm_priv)
> +               return;
> +

This is wrong - buffers that are supposed to be dropped should return
to bm_pool.

> @@ -1587,23 +1812,35 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
>
>         rx_done = 0;
>
> +       bm_in_use = pp->bm_priv ? true : false;
> +
>         /* Fairness NAPI loop */
>         while (rx_done < rx_todo) {
>                 struct mvneta_rx_desc *rx_desc = mvneta_rxq_next_desc_get(rxq);
> +               struct mvneta_bm_pool *bm_pool = NULL;
>                 struct sk_buff *skb;
>                 unsigned char *data;
>                 dma_addr_t phys_addr;
> -               u32 rx_status;
> +               u32 rx_status, frag_size;
>                 int rx_bytes, err;
> +               u8 pool_id;
>
>                 rx_done++;
>                 rx_status = rx_desc->status;
>                 rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE);
>                 data = (unsigned char *)rx_desc->buf_cookie;
>                 phys_addr = rx_desc->buf_phys_addr;
> +               if (bm_in_use) {
> +                       pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_desc);
> +                       bm_pool = &pp->bm_priv->bm_pools[pool_id];
> +               }
>
>                 if (!mvneta_rxq_desc_is_first_last(rx_status) ||
>                     (rx_status & MVNETA_RXD_ERR_SUMMARY)) {
> +                       /* Return the buffer to the pool */
> +                       if (bm_in_use)
> +                               mvneta_bm_pool_put_bp(pp->bm_priv, bm_pool,
> +                                                     rx_desc->buf_phys_addr);
>                 err_drop_frame:
>                         dev->stats.rx_errors++;
>                         mvneta_rx_error(pp, rx_desc);
> @@ -1633,25 +1870,38 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
>                         rcvd_pkts++;
>                         rcvd_bytes += rx_bytes;
>
> +                       /* Return the buffer to the pool */
> +                       if (bm_in_use)
> +                               mvneta_bm_pool_put_bp(pp->bm_priv, bm_pool,
> +                                                     rx_desc->buf_phys_addr);
> +
>                         /* leave the descriptor and buffer untouched */
>                         continue;
>                 }
>
>                 /* Refill processing */
> -               err = mvneta_rx_refill(pp, rx_desc);
> +               err = bm_in_use ? mvneta_bm_pool_refill(pp->bm_priv, bm_pool) :
> +                                 mvneta_rx_refill(pp, rx_desc);
>                 if (err) {
>                         netdev_err(dev, "Linux processing - Can't refill\n");
>                         rxq->missed++;
>                         goto err_drop_frame;

Wrong - on refill fail, original buffer should be returned to bm_pool.
Same case is, when netdev_alloc_skb_ip_align fail inside copybreak
(this should also be fixed).

Best regards,
Marcin