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Message-ID: <b1d0ca22-de75-4d76-90ba-62c2a57f4301@bp.renesas.com>
Date: Mon, 15 Apr 2024 13:18:08 +0100
From: Paul Barker <paul.barker.ct@...renesas.com>
To: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Cc: Sergey Shtylyov <s.shtylyov@....ru>, "David S. Miller"
<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Geert Uytterhoeven <geert+renesas@...der.be>, netdev@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next RFC v3 3/7] net: ravb: Refactor RX ring refill
On 15/04/2024 12:57, Niklas Söderlund wrote:
> Hi Paul,
>
> Thanks for your work, I really like this deduplication of code!
>
> On 2024-04-15 10:48:00 +0100, Paul Barker wrote:
>> To reduce code duplication, we add a new RX ring refill function which
>> can handle both the initial RX ring population (which was split between
>> ravb_ring_init() and ravb_ring_format()) and the RX ring refill after
>> polling (in ravb_rx()).
>>
>> Signed-off-by: Paul Barker <paul.barker.ct@...renesas.com>
>> ---
>> drivers/net/ethernet/renesas/ravb_main.c | 141 +++++++++--------------
>> 1 file changed, 52 insertions(+), 89 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index 1ac599a044b2..baa01bd81f2d 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -317,35 +317,42 @@ static void ravb_ring_free(struct net_device *ndev, int q)
>> priv->tx_skb[q] = NULL;
>> }
>>
>> -static void ravb_rx_ring_format(struct net_device *ndev, int q)
>> +static u32
>> +ravb_rx_ring_refill(struct net_device *ndev, int q, u32 count, gfp_t gfp_mask)
>> {
>> struct ravb_private *priv = netdev_priv(ndev);
>> + const struct ravb_hw_info *info = priv->info;
>> struct ravb_rx_desc *rx_desc;
>> - unsigned int rx_ring_size;
>> dma_addr_t dma_addr;
>> - unsigned int i;
>> + u32 i, entry;
>>
>> - rx_ring_size = priv->info->rx_desc_size * priv->num_rx_ring[q];
>> - memset(priv->rx_ring[q].raw, 0, rx_ring_size);
>> - /* Build RX ring buffer */
>> - for (i = 0; i < priv->num_rx_ring[q]; i++) {
>> - /* RX descriptor */
>> - rx_desc = ravb_rx_get_desc(priv, q, i);
>> - rx_desc->ds_cc = cpu_to_le16(priv->info->rx_max_desc_use);
>> - dma_addr = dma_map_single(ndev->dev.parent, priv->rx_skb[q][i]->data,
>> - priv->info->rx_max_frame_size,
>> - DMA_FROM_DEVICE);
>> - /* We just set the data size to 0 for a failed mapping which
>> - * should prevent DMA from happening...
>> - */
>> - if (dma_mapping_error(ndev->dev.parent, dma_addr))
>> - rx_desc->ds_cc = cpu_to_le16(0);
>> - rx_desc->dptr = cpu_to_le32(dma_addr);
>> + for (i = 0; i < count; i++) {
>> + entry = (priv->dirty_rx[q] + i) % priv->num_rx_ring[q];
>> + rx_desc = ravb_rx_get_desc(priv, q, entry);
>> + rx_desc->ds_cc = cpu_to_le16(info->rx_max_desc_use);
>> +
>> + if (!priv->rx_skb[q][entry]) {
>> + priv->rx_skb[q][entry] = ravb_alloc_skb(ndev, info, gfp_mask);
>> + if (!priv->rx_skb[q][entry])
>> + break;
>> + dma_addr = dma_map_single(ndev->dev.parent,
>> + priv->rx_skb[q][entry]->data,
>> + priv->info->rx_max_frame_size,
>> + DMA_FROM_DEVICE);
>> + skb_checksum_none_assert(priv->rx_skb[q][entry]);
>> + /* We just set the data size to 0 for a failed mapping
>> + * which should prevent DMA from happening...
>> + */
>> + if (dma_mapping_error(ndev->dev.parent, dma_addr))
>> + rx_desc->ds_cc = cpu_to_le16(0);
>> + rx_desc->dptr = cpu_to_le32(dma_addr);
>> + }
>> + /* Descriptor type must be set after all the above writes */
>> + dma_wmb();
>> rx_desc->die_dt = DT_FEMPTY;
>> }
>> - rx_desc = ravb_rx_get_desc(priv, q, i);
>> - rx_desc->dptr = cpu_to_le32((u32)priv->rx_desc_dma[q]);
>> - rx_desc->die_dt = DT_LINKFIX; /* type */
>> +
>> + return i;
>> }
>>
>> /* Format skb and descriptor buffer for Ethernet AVB */
>> @@ -353,6 +360,7 @@ static void ravb_ring_format(struct net_device *ndev, int q)
>> {
>> struct ravb_private *priv = netdev_priv(ndev);
>> unsigned int num_tx_desc = priv->num_tx_desc;
>> + struct ravb_rx_desc *rx_desc;
>> struct ravb_tx_desc *tx_desc;
>> struct ravb_desc *desc;
>> unsigned int tx_ring_size = sizeof(*tx_desc) * priv->num_tx_ring[q] *
>> @@ -364,8 +372,6 @@ static void ravb_ring_format(struct net_device *ndev, int q)
>> priv->dirty_rx[q] = 0;
>> priv->dirty_tx[q] = 0;
>>
>> - ravb_rx_ring_format(ndev, q);
>> -
>> memset(priv->tx_ring[q], 0, tx_ring_size);
>> /* Build TX ring buffer */
>> for (i = 0, tx_desc = priv->tx_ring[q]; i < priv->num_tx_ring[q];
>> @@ -379,6 +385,14 @@ static void ravb_ring_format(struct net_device *ndev, int q)
>> tx_desc->dptr = cpu_to_le32((u32)priv->tx_desc_dma[q]);
>> tx_desc->die_dt = DT_LINKFIX; /* type */
>>
>> + /* Regular RX descriptors have already been initialized by
>> + * ravb_rx_ring_refill(), we just need to initialize the final link
>> + * descriptor.
>> + */
>> + rx_desc = ravb_rx_get_desc(priv, q, priv->num_rx_ring[q]);
>> + rx_desc->dptr = cpu_to_le32((u32)priv->rx_desc_dma[q]);
>> + rx_desc->die_dt = DT_LINKFIX; /* type */
>> +
>
> super-nit: Should you not move this addition up to where you removed the
> call to ravb_rx_ring_format()? Before this change the order of things
> are,
>
> /* Init RX ring */
> /* Init TX ring */
> /* Set RX descriptor base address */
> /* Set TX descriptor base address */
>
>
> While after it is,
>
> /* Init TX ring */
> /* Init RX ring */
> /* Set RX descriptor base address */
> /* Set TX descriptor base address */
>
> My OCD is itching ;-)
Since I'll need to re-spin this series anyway, I may as well tidy that
up :)
>
>> /* RX descriptor base address for best effort */
>> desc = &priv->desc_bat[RX_QUEUE_OFFSET + q];
>> desc->die_dt = DT_LINKFIX; /* type */
>> @@ -408,11 +422,9 @@ static void *ravb_alloc_rx_desc(struct net_device *ndev, int q)
>> static int ravb_ring_init(struct net_device *ndev, int q)
>> {
>> struct ravb_private *priv = netdev_priv(ndev);
>> - const struct ravb_hw_info *info = priv->info;
>> unsigned int num_tx_desc = priv->num_tx_desc;
>> unsigned int ring_size;
>> - struct sk_buff *skb;
>> - unsigned int i;
>> + u32 num_filled;
>>
>> /* Allocate RX and TX skb rings */
>> priv->rx_skb[q] = kcalloc(priv->num_rx_ring[q],
>> @@ -422,13 +434,6 @@ static int ravb_ring_init(struct net_device *ndev, int q)
>> if (!priv->rx_skb[q] || !priv->tx_skb[q])
>> goto error;
>>
>> - for (i = 0; i < priv->num_rx_ring[q]; i++) {
>> - skb = ravb_alloc_skb(ndev, info, GFP_KERNEL);
>> - if (!skb)
>> - goto error;
>> - priv->rx_skb[q][i] = skb;
>> - }
>> -
>> if (num_tx_desc > 1) {
>> /* Allocate rings for the aligned buffers */
>> priv->tx_align[q] = kmalloc(DPTR_ALIGN * priv->num_tx_ring[q] +
>> @@ -443,6 +448,13 @@ static int ravb_ring_init(struct net_device *ndev, int q)
>>
>> priv->dirty_rx[q] = 0;
>>
>> + /* Populate RX ring buffer. */
>> + ring_size = priv->info->rx_desc_size * priv->num_rx_ring[q];
>> + memset(priv->rx_ring[q].raw, 0, ring_size);
>> + num_filled = ravb_rx_ring_refill(ndev, q, priv->num_rx_ring[q], GFP_KERNEL);
>> + if (num_filled != priv->num_rx_ring[q])
>> + goto error;
>> +
>
> Here you also change the order, but it make sense here as you first deal
> with all TX and then all RX ;-)
The placement here is because we can't call ravb_rx_ring_refill() until
priv->dirty_rx[q] has been zero'd.
The init order right now is actually:
RX page pool
RX buffers
TX SKBs
RX descriptors
RX ring buffer
TX descriptors
So maybe this should be re-ordered.
I considered breaking this all apart, so ravb_ring_init() would call
ravb_rx_ring_init()/ravb_tx_ring_init() and ravb_ring_format() would
call ravb_rx_ring_format()/ravb_tx_ring_format(). There are several
steps happening for TX & RX in both init and format stages. Does that
sound cleaner to you?
Thanks,
--
Paul Barker
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