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Message-ID: <87wpfmfv4t.fsf@free-electrons.com>
Date: Tue, 29 Nov 2016 11:17:06 +0100
From: Gregory CLEMENT <gregory.clement@...e-electrons.com>
To: Marcin Wojtas <mw@...ihalf.com>
Cc: "David S. Miller" <davem@...emloft.net>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
Jisheng Zhang <jszhang@...vell.com>,
Arnd Bergmann <arnd@...db.de>,
Jason Cooper <jason@...edaemon.net>,
Andrew Lunn <andrew@...n.ch>,
Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
"linux-arm-kernel\@lists.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Nadav Haklai <nadavh@...vell.com>,
Dmitri Epshtein <dima@...vell.com>,
Yelena Krivosheev <yelena@...vell.com>
Subject: Re: [PATCH v3 net-next 2/6] net: mvneta: Use cacheable memory to store the rx buffer virtual address
Hi Marcin,
On mar., nov. 29 2016, Marcin Wojtas <mw@...ihalf.com> wrote:
> Hi Gregory,
>
> Apparently HWBM had a mistake in implementation, please see below.
>
> 2016-11-29 10:37 GMT+01:00 Gregory CLEMENT <gregory.clement@...e-electrons.com>:
>> Until now the virtual address of the received buffer were stored in the
>> cookie field of the rx descriptor. However, this field is 32-bits only
>> which prevents to use the driver on a 64-bits architecture.
>>
>> With this patch the virtual address is stored in an array not shared with
>> the hardware (no more need to use the DMA API). Thanks to this, it is
>> possible to use cache contrary to the access of the rx descriptor member.
>>
>> The change is done in the swbm path only because the hwbm uses the cookie
>> field, this also means that currently the hwbm is not usable in 64-bits.
>>
>> Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
>> ---
>> drivers/net/ethernet/marvell/mvneta.c | 93 ++++++++++++++++++++++++----
>> 1 file changed, 81 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
>> index 1b84f746d748..32b142d0e44e 100644
>> --- a/drivers/net/ethernet/marvell/mvneta.c
>> +++ b/drivers/net/ethernet/marvell/mvneta.c
>> @@ -561,6 +561,9 @@ struct mvneta_rx_queue {
>> u32 pkts_coal;
>> u32 time_coal;
>>
>> + /* Virtual address of the RX buffer */
>> + void **buf_virt_addr;
>> +
>> /* Virtual address of the RX DMA descriptors array */
>> struct mvneta_rx_desc *descs;
>>
>> @@ -1573,10 +1576,14 @@ static void mvneta_tx_done_pkts_coal_set(struct mvneta_port *pp,
>>
>> /* Handle rx descriptor fill by setting buf_cookie and buf_phys_addr */
>> static void mvneta_rx_desc_fill(struct mvneta_rx_desc *rx_desc,
>> - u32 phys_addr, u32 cookie)
>> + u32 phys_addr, void *virt_addr,
>> + struct mvneta_rx_queue *rxq)
>> {
>> - rx_desc->buf_cookie = cookie;
>> + int i;
>> +
>> rx_desc->buf_phys_addr = phys_addr;
>> + i = rx_desc - rxq->descs;
>> + rxq->buf_virt_addr[i] = virt_addr;
>> }
>>
>> /* Decrement sent descriptors counter */
>> @@ -1781,7 +1788,8 @@ EXPORT_SYMBOL_GPL(mvneta_frag_free);
>>
>> /* Refill processing for SW buffer management */
>> static int mvneta_rx_refill(struct mvneta_port *pp,
>> - struct mvneta_rx_desc *rx_desc)
>> + struct mvneta_rx_desc *rx_desc,
>> + struct mvneta_rx_queue *rxq)
>>
>> {
>> dma_addr_t phys_addr;
>> @@ -1799,7 +1807,7 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
>> return -ENOMEM;
>> }
>>
>> - mvneta_rx_desc_fill(rx_desc, phys_addr, (u32)data);
>> + mvneta_rx_desc_fill(rx_desc, phys_addr, data, rxq);
>> return 0;
>> }
>>
>> @@ -1861,7 +1869,12 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp,
>>
>> for (i = 0; i < rxq->size; i++) {
>> struct mvneta_rx_desc *rx_desc = rxq->descs + i;
>> - void *data = (void *)rx_desc->buf_cookie;
>> + void *data;
>> +
>> + if (!pp->bm_priv)
>> + data = rxq->buf_virt_addr[i];
>> + else
>> + data = (void *)(uintptr_t)rx_desc->buf_cookie;
>>
>> dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr,
>> MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
>> @@ -1894,12 +1907,13 @@ static int mvneta_rx_swbm(struct mvneta_port *pp, int rx_todo,
>> unsigned char *data;
>> dma_addr_t phys_addr;
>> u32 rx_status, frag_size;
>> - int rx_bytes, err;
>> + int rx_bytes, err, index;
>>
>> 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;
>> + index = rx_desc - rxq->descs;
>> + data = (unsigned char *)rxq->buf_virt_addr[index];
>> phys_addr = rx_desc->buf_phys_addr;
>>
>> if (!mvneta_rxq_desc_is_first_last(rx_status) ||
>> @@ -1938,7 +1952,7 @@ static int mvneta_rx_swbm(struct mvneta_port *pp, int rx_todo,
>> }
>>
>> /* Refill processing */
>> - err = mvneta_rx_refill(pp, rx_desc);
>> + err = mvneta_rx_refill(pp, rx_desc, rxq);
>> if (err) {
>> netdev_err(dev, "Linux processing - Can't refill\n");
>> rxq->missed++;
>> @@ -2020,7 +2034,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo,
>> 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;
>> + data = (u8 *)(uintptr_t)rx_desc->buf_cookie;
>> phys_addr = rx_desc->buf_phys_addr;
>> pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_desc);
>> bm_pool = &pp->bm_priv->bm_pools[pool_id];
>> @@ -2708,6 +2722,56 @@ static int mvneta_poll(struct napi_struct *napi, int budget)
>> return rx_done;
>> }
>>
>> +/* Refill processing for HW buffer management */
>> +static int mvneta_rx_hwbm_refill(struct mvneta_port *pp,
>> + struct mvneta_rx_desc *rx_desc)
>> +
>> +{
>> + dma_addr_t phys_addr;
>> + void *data;
>> +
>> + data = mvneta_frag_alloc(pp->frag_size);
>> + if (!data)
>> + return -ENOMEM;
>> +
>> + phys_addr = dma_map_single(pp->dev->dev.parent, data,
>> + MVNETA_RX_BUF_SIZE(pp->pkt_size),
>> + DMA_FROM_DEVICE);
>> + if (unlikely(dma_mapping_error(pp->dev->dev.parent, phys_addr))) {
>> + mvneta_frag_free(pp->frag_size, data);
>> + return -ENOMEM;
>> + }
>> +
>> + rx_desc->buf_phys_addr = phys_addr;
>> + rx_desc->buf_cookie = (uintptr_t)data;
>> +
>> + return 0;
>> +}
>> +
>> +/* Handle rxq fill: allocates rxq skbs; called when initializing a port */
>> +static int mvneta_rxq_bm_fill(struct mvneta_port *pp,
>> + struct mvneta_rx_queue *rxq,
>> + int num)
>> +{
>> + int i;
>> +
>> + for (i = 0; i < num; i++) {
>> + memset(rxq->descs + i, 0, sizeof(struct mvneta_rx_desc));
>> + if (mvneta_rx_hwbm_refill(pp, rxq->descs + i) != 0) {
>> + netdev_err(pp->dev, "%s:rxq %d, %d of %d buffs filled\n",
>> + __func__, rxq->id, i, num);
>> + break;
>> + }
>> + }
>> +
>> + /* Add this number of RX descriptors as non occupied (ready to
>> + * get packets)
>> + */
>> + mvneta_rxq_non_occup_desc_add(pp, rxq, i);
>> +
>> + return i;
>> +}
>> +
>> /* Handle rxq fill: allocates rxq skbs; called when initializing a port */
>> static int mvneta_rxq_fill(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
>> int num)
>> @@ -2716,7 +2780,7 @@ static int mvneta_rxq_fill(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
>>
>> for (i = 0; i < num; i++) {
>> memset(rxq->descs + i, 0, sizeof(struct mvneta_rx_desc));
>> - if (mvneta_rx_refill(pp, rxq->descs + i) != 0) {
>> + if (mvneta_rx_refill(pp, rxq->descs + i, rxq) != 0) {
>> netdev_err(pp->dev, "%s:rxq %d, %d of %d buffs filled\n",
>> __func__, rxq->id, i, num);
>> break;
>> @@ -2784,14 +2848,14 @@ static int mvneta_rxq_init(struct mvneta_port *pp,
>> mvneta_rxq_buf_size_set(pp, rxq,
>> MVNETA_RX_BUF_SIZE(pp->pkt_size));
>> mvneta_rxq_bm_disable(pp, rxq);
>> + mvneta_rxq_fill(pp, rxq, rxq->size);
>> } else {
>> mvneta_rxq_bm_enable(pp, rxq);
>> mvneta_rxq_long_pool_set(pp, rxq);
>> mvneta_rxq_short_pool_set(pp, rxq);
>> + mvneta_rxq_bm_fill(pp, rxq, rxq->size);
>
> Manual filling descriptors with new buffers is redundant. For HWBM,
> all buffers are allocated in mvneta_bm_construct() and in runtime they
> are put into descriptors by hardware. I think it's enough to add here:
> mvneta_rxq_non_occup_desc_add(pp, rxq, rxq->size);
>
> And remove mvneta_rxq_bm_fill and mvneta_rx_hwbm_refill.
You're right. I will do it it will simplify the code.
Thanks,
Gregory
>
> Best regards,
> Marcin
--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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