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Message-ID: <152b032e-fcd9-4d49-8154-92a475c0670c@kernel.org>
Date: Wed, 12 Feb 2025 15:56:09 +0200
From: Roger Quadros <rogerq@...nel.org>
To: Meghana Malladi <m-malladi@...com>, danishanwar@...com,
pabeni@...hat.com, kuba@...nel.org, edumazet@...gle.com,
davem@...emloft.net, andrew+netdev@...n.ch
Cc: bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
u.kleine-koenig@...libre.com, krzysztof.kozlowski@...aro.org,
dan.carpenter@...aro.org, schnelle@...ux.ibm.com, glaroque@...libre.com,
rdunlap@...radead.org, diogo.ivo@...mens.com, jan.kiszka@...mens.com,
john.fastabend@...il.com, hawk@...nel.org, daniel@...earbox.net,
ast@...nel.org, srk@...com, Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [PATCH net-next v2 1/3] net: ti: icssg-prueth: Use page_pool API
for RX buffer allocation
On 10/02/2025 12:33, Meghana Malladi wrote:
> From: Roger Quadros <rogerq@...nel.org>
>
> This is to prepare for native XDP support.
>
> The page pool API is more faster in allocating pages than
> __alloc_skb(). Drawback is that it works at PAGE_SIZE granularity
> so we are not efficient in memory usage.
> i.e. we are using PAGE_SIZE (4KB) memory for 1.5KB max packet size.
>
> Signed-off-by: Roger Quadros <rogerq@...nel.org>
> Signed-off-by: MD Danish Anwar <danishanwar@...com>
> Signed-off-by: Meghana Malladi <m-malladi@...com>
> ---
> v1: https://lore.kernel.org/all/20250122124951.3072410-1-m-malladi@ti.com/
>
> Changes since v1 (v2-v1):
> - Recycle pages wherever necessary using skb_mark_for_recycle()
> - Use napi_build_skb() instead of build_skb()
> - Update with correct frag_size argument in napi_build_skb()
> - Use napi_gro_receive() instead of netif_receive_skb()
> - Use PP_FLAG_DMA_SYNC_DEV to enable DMA sync with device
> - Use page_pool_dma_sync_for_cpu() to sync Rx page pool for CPU
>
> All the above changes have been suggested by Ido Schimmel <idosch@...sch.org>
>
> drivers/net/ethernet/ti/Kconfig | 1 +
> drivers/net/ethernet/ti/icssg/icssg_common.c | 174 ++++++++++++------
> drivers/net/ethernet/ti/icssg/icssg_prueth.h | 14 +-
> .../net/ethernet/ti/icssg/icssg_prueth_sr1.c | 21 ++-
> 4 files changed, 140 insertions(+), 70 deletions(-)
>
> diff --git a/drivers/net/ethernet/ti/Kconfig b/drivers/net/ethernet/ti/Kconfig
> index 0d5a862cd78a..b461281d31b6 100644
> --- a/drivers/net/ethernet/ti/Kconfig
> +++ b/drivers/net/ethernet/ti/Kconfig
> @@ -204,6 +204,7 @@ config TI_ICSSG_PRUETH_SR1
> select PHYLIB
> select TI_ICSS_IEP
> select TI_K3_CPPI_DESC_POOL
> + select PAGE_POOL
> depends on PRU_REMOTEPROC
> depends on NET_SWITCHDEV
> depends on ARCH_K3 && OF && TI_K3_UDMA_GLUE_LAYER
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
> index 74f0f200a89d..c3c1e2bf461e 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_common.c
> +++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
> @@ -45,6 +45,11 @@ void prueth_cleanup_rx_chns(struct prueth_emac *emac,
> struct prueth_rx_chn *rx_chn,
> int max_rflows)
> {
> + if (rx_chn->pg_pool) {
> + page_pool_destroy(rx_chn->pg_pool);
> + rx_chn->pg_pool = NULL;
> + }
> +
> if (rx_chn->desc_pool)
> k3_cppi_desc_pool_destroy(rx_chn->desc_pool);
>
> @@ -461,17 +466,17 @@ int prueth_init_rx_chns(struct prueth_emac *emac,
> }
> EXPORT_SYMBOL_GPL(prueth_init_rx_chns);
>
> -int prueth_dma_rx_push(struct prueth_emac *emac,
> - struct sk_buff *skb,
> - struct prueth_rx_chn *rx_chn)
> +int prueth_dma_rx_push_mapped(struct prueth_emac *emac,
> + struct prueth_rx_chn *rx_chn,
> + struct page *page, u32 buf_len)
> {
> struct net_device *ndev = emac->ndev;
> struct cppi5_host_desc_t *desc_rx;
> - u32 pkt_len = skb_tailroom(skb);
> dma_addr_t desc_dma;
> dma_addr_t buf_dma;
> void **swdata;
>
> + buf_dma = page_pool_get_dma_addr(page) + PRUETH_HEADROOM;
> desc_rx = k3_cppi_desc_pool_alloc(rx_chn->desc_pool);
> if (!desc_rx) {
> netdev_err(ndev, "rx push: failed to allocate descriptor\n");
> @@ -479,25 +484,18 @@ int prueth_dma_rx_push(struct prueth_emac *emac,
> }
> desc_dma = k3_cppi_desc_pool_virt2dma(rx_chn->desc_pool, desc_rx);
>
> - buf_dma = dma_map_single(rx_chn->dma_dev, skb->data, pkt_len, DMA_FROM_DEVICE);
> - if (unlikely(dma_mapping_error(rx_chn->dma_dev, buf_dma))) {
> - k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
> - netdev_err(ndev, "rx push: failed to map rx pkt buffer\n");
> - return -EINVAL;
> - }
> -
> cppi5_hdesc_init(desc_rx, CPPI5_INFO0_HDESC_EPIB_PRESENT,
> PRUETH_NAV_PS_DATA_SIZE);
> k3_udma_glue_rx_dma_to_cppi5_addr(rx_chn->rx_chn, &buf_dma);
> - cppi5_hdesc_attach_buf(desc_rx, buf_dma, skb_tailroom(skb), buf_dma, skb_tailroom(skb));
> + cppi5_hdesc_attach_buf(desc_rx, buf_dma, buf_len, buf_dma, buf_len);
>
> swdata = cppi5_hdesc_get_swdata(desc_rx);
> - *swdata = skb;
> + *swdata = page;
>
> - return k3_udma_glue_push_rx_chn(rx_chn->rx_chn, 0,
> + return k3_udma_glue_push_rx_chn(rx_chn->rx_chn, PRUETH_RX_FLOW_DATA,
> desc_rx, desc_dma);
> }
> -EXPORT_SYMBOL_GPL(prueth_dma_rx_push);
> +EXPORT_SYMBOL_GPL(prueth_dma_rx_push_mapped);
>
> u64 icssg_ts_to_ns(u32 hi_sw, u32 hi, u32 lo, u32 cycle_time_ns)
> {
> @@ -541,12 +539,16 @@ static int emac_rx_packet(struct prueth_emac *emac, u32 flow_id)
> u32 buf_dma_len, pkt_len, port_id = 0;
> struct net_device *ndev = emac->ndev;
> struct cppi5_host_desc_t *desc_rx;
> - struct sk_buff *skb, *new_skb;
> dma_addr_t desc_dma, buf_dma;
> + struct page *page, *new_page;
> + struct page_pool *pool;
> + struct sk_buff *skb;
> void **swdata;
> u32 *psdata;
> + void *pa;
> int ret;
>
> + pool = rx_chn->pg_pool;
> ret = k3_udma_glue_pop_rx_chn(rx_chn->rx_chn, flow_id, &desc_dma);
> if (ret) {
> if (ret != -ENODATA)
> @@ -558,15 +560,10 @@ static int emac_rx_packet(struct prueth_emac *emac, u32 flow_id)
> return 0;
>
> desc_rx = k3_cppi_desc_pool_dma2virt(rx_chn->desc_pool, desc_dma);
> -
> swdata = cppi5_hdesc_get_swdata(desc_rx);
> - skb = *swdata;
> -
> - psdata = cppi5_hdesc_get_psdata(desc_rx);
> - /* RX HW timestamp */
> - if (emac->rx_ts_enabled)
> - emac_rx_timestamp(emac, skb, psdata);
> + page = *swdata;
>
Unnecessary blank line.
> + page_pool_dma_sync_for_cpu(pool, page, 0, PAGE_SIZE);
> cppi5_hdesc_get_obuf(desc_rx, &buf_dma, &buf_dma_len);
> k3_udma_glue_rx_cppi5_to_dma_addr(rx_chn->rx_chn, &buf_dma);
> pkt_len = cppi5_hdesc_get_pktlen(desc_rx);
> @@ -574,32 +571,51 @@ static int emac_rx_packet(struct prueth_emac *emac, u32 flow_id)
> pkt_len -= 4;
> cppi5_desc_get_tags_ids(&desc_rx->hdr, &port_id, NULL);
>
> - dma_unmap_single(rx_chn->dma_dev, buf_dma, buf_dma_len, DMA_FROM_DEVICE);
> k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
>
> - skb->dev = ndev;
> - new_skb = netdev_alloc_skb_ip_align(ndev, PRUETH_MAX_PKT_SIZE);
> /* if allocation fails we drop the packet but push the
> - * descriptor back to the ring with old skb to prevent a stall
> + * descriptor back to the ring with old page to prevent a stall
> */
> - if (!new_skb) {
> + new_page = page_pool_dev_alloc_pages(pool);
> + if (unlikely(!new_page)) {
> + new_page = page;
> ndev->stats.rx_dropped++;
> - new_skb = skb;
> - } else {
> - /* send the filled skb up the n/w stack */
> - skb_put(skb, pkt_len);
> - if (emac->prueth->is_switch_mode)
> - skb->offload_fwd_mark = emac->offload_fwd_mark;
> - skb->protocol = eth_type_trans(skb, ndev);
> - napi_gro_receive(&emac->napi_rx, skb);
> - ndev->stats.rx_bytes += pkt_len;
> - ndev->stats.rx_packets++;
> + goto requeue;
> + }
> +
> + /* prepare skb and send to n/w stack */
> + pa = page_address(page);
> + skb = napi_build_skb(pa, PAGE_SIZE);
> + if (!skb) {
> + ndev->stats.rx_dropped++;
> + page_pool_recycle_direct(pool, page);
> + goto requeue;
> }
>
> + skb_reserve(skb, PRUETH_HEADROOM);
> + skb_put(skb, pkt_len);
> + skb->dev = ndev;
> +
> + psdata = cppi5_hdesc_get_psdata(desc_rx);
> + /* RX HW timestamp */
> + if (emac->rx_ts_enabled)
> + emac_rx_timestamp(emac, skb, psdata);
> +
> + if (emac->prueth->is_switch_mode)
> + skb->offload_fwd_mark = emac->offload_fwd_mark;
> + skb->protocol = eth_type_trans(skb, ndev);
> +
> + skb_mark_for_recycle(skb);
> + napi_gro_receive(&emac->napi_rx, skb);
> + ndev->stats.rx_bytes += pkt_len;
> + ndev->stats.rx_packets++;
> +
> +requeue:
> /* queue another RX DMA */
> - ret = prueth_dma_rx_push(emac, new_skb, &emac->rx_chns);
> + ret = prueth_dma_rx_push_mapped(emac, &emac->rx_chns, new_page,
> + PRUETH_MAX_PKT_SIZE);
> if (WARN_ON(ret < 0)) {
> - dev_kfree_skb_any(new_skb);
> + page_pool_recycle_direct(pool, new_page);
> ndev->stats.rx_errors++;
> ndev->stats.rx_dropped++;
> }
> @@ -611,22 +627,17 @@ static void prueth_rx_cleanup(void *data, dma_addr_t desc_dma)
> {
> struct prueth_rx_chn *rx_chn = data;
> struct cppi5_host_desc_t *desc_rx;
> - struct sk_buff *skb;
> - dma_addr_t buf_dma;
> - u32 buf_dma_len;
> + struct page_pool *pool;
> + struct page *page;
> void **swdata;
>
> + pool = rx_chn->pg_pool;
> +
here too.
> desc_rx = k3_cppi_desc_pool_dma2virt(rx_chn->desc_pool, desc_dma);
> swdata = cppi5_hdesc_get_swdata(desc_rx);
> - skb = *swdata;
> - cppi5_hdesc_get_obuf(desc_rx, &buf_dma, &buf_dma_len);
> - k3_udma_glue_rx_cppi5_to_dma_addr(rx_chn->rx_chn, &buf_dma);
> -
> - dma_unmap_single(rx_chn->dma_dev, buf_dma, buf_dma_len,
> - DMA_FROM_DEVICE);
> + page = *swdata;
> + page_pool_recycle_direct(pool, page);
> k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
> -
> - dev_kfree_skb_any(skb);
> }
>
> static int prueth_tx_ts_cookie_get(struct prueth_emac *emac)
> @@ -907,29 +918,71 @@ int icssg_napi_rx_poll(struct napi_struct *napi_rx, int budget)
> }
> EXPORT_SYMBOL_GPL(icssg_napi_rx_poll);
>
> +static struct page_pool *prueth_create_page_pool(struct prueth_emac *emac,
> + struct device *dma_dev,
> + int size)
> +{
> + struct page_pool_params pp_params = { 0 };
> + struct page_pool *pool;
> +
> + pp_params.order = 0;
> + pp_params.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV;
> + pp_params.pool_size = size;
> + pp_params.nid = dev_to_node(emac->prueth->dev);
> + pp_params.dma_dir = DMA_BIDIRECTIONAL;
> + pp_params.dev = dma_dev;
> + pp_params.napi = &emac->napi_rx;
> + pp_params.max_len = PAGE_SIZE;
> +
> + pool = page_pool_create(&pp_params);
> + if (IS_ERR(pool))
> + netdev_err(emac->ndev, "cannot create rx page pool\n");
> +
> + return pool;
> +}
> +
> int prueth_prepare_rx_chan(struct prueth_emac *emac,
> struct prueth_rx_chn *chn,
> int buf_size)
> {
> - struct sk_buff *skb;
> + struct page_pool *pool;
> + struct page *page;
> int i, ret;
>
> + pool = prueth_create_page_pool(emac, chn->dma_dev, chn->descs_num);
> + if (IS_ERR(pool))
> + return PTR_ERR(pool);
> +
> + chn->pg_pool = pool;
> +
> for (i = 0; i < chn->descs_num; i++) {
> - skb = __netdev_alloc_skb_ip_align(NULL, buf_size, GFP_KERNEL);
> - if (!skb)
> - return -ENOMEM;
> + /* NOTE: we're not using memory efficiently here.
> + * 1 full page (4KB?) used here instead of
> + * PRUETH_MAX_PKT_SIZE (~1.5KB?)
> + */
> + page = page_pool_dev_alloc_pages(pool);
Did you evaluate Ido's suggestion to use page_pool_alloc_frag()?
> + if (!page) {
> + netdev_err(emac->ndev, "couldn't allocate rx page\n");
> + ret = -ENOMEM;
> + goto recycle_alloc_pg;
> + }
>
> - ret = prueth_dma_rx_push(emac, skb, chn);
> + ret = prueth_dma_rx_push_mapped(emac, chn, page, buf_size);
> if (ret < 0) {
> netdev_err(emac->ndev,
> - "cannot submit skb for rx chan %s ret %d\n",
> + "cannot submit page for rx chan %s ret %d\n",
> chn->name, ret);
> - kfree_skb(skb);
> - return ret;
> + page_pool_recycle_direct(pool, page);
> + goto recycle_alloc_pg;
> }
> }
>
> return 0;
> +
> +recycle_alloc_pg:
> + prueth_reset_rx_chan(&emac->rx_chns, PRUETH_MAX_RX_FLOWS, false);
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(prueth_prepare_rx_chan);
>
> @@ -958,6 +1011,9 @@ void prueth_reset_rx_chan(struct prueth_rx_chn *chn,
> prueth_rx_cleanup, !!i);
> if (disable)
> k3_udma_glue_disable_rx_chn(chn->rx_chn);
> +
> + page_pool_destroy(chn->pg_pool);
> + chn->pg_pool = NULL;
> }
> EXPORT_SYMBOL_GPL(prueth_reset_rx_chan);
>
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth.h b/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> index 329b46e9ee53..c7b906de18af 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> +++ b/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> @@ -33,6 +33,8 @@
> #include <linux/dma/k3-udma-glue.h>
>
> #include <net/devlink.h>
> +#include <net/xdp.h>
> +#include <net/page_pool/helpers.h>
>
> #include "icssg_config.h"
> #include "icss_iep.h"
> @@ -131,6 +133,7 @@ struct prueth_rx_chn {
> u32 descs_num;
> unsigned int irq[ICSSG_MAX_RFLOWS]; /* separate irq per flow */
> char name[32];
> + struct page_pool *pg_pool;
> };
>
> /* There are 4 Tx DMA channels, but the highest priority is CH3 (thread 3)
> @@ -210,6 +213,10 @@ struct prueth_emac {
> struct netdev_hw_addr_list vlan_mcast_list[MAX_VLAN_ID];
> };
>
> +/* The buf includes headroom compatible with both skb and xdpf */
> +#define PRUETH_HEADROOM_NA (max(XDP_PACKET_HEADROOM, NET_SKB_PAD) + NET_IP_ALIGN)
> +#define PRUETH_HEADROOM ALIGN(PRUETH_HEADROOM_NA, sizeof(long))
> +
> /**
> * struct prueth_pdata - PRUeth platform data
> * @fdqring_mode: Free desc queue mode
> @@ -410,9 +417,10 @@ int prueth_init_rx_chns(struct prueth_emac *emac,
> struct prueth_rx_chn *rx_chn,
> char *name, u32 max_rflows,
> u32 max_desc_num);
> -int prueth_dma_rx_push(struct prueth_emac *emac,
> - struct sk_buff *skb,
> - struct prueth_rx_chn *rx_chn);
> +int prueth_dma_rx_push_mapped(struct prueth_emac *emac,
> + struct prueth_rx_chn *rx_chn,
> + struct page *page, u32 buf_len);
> +unsigned int prueth_rxbuf_total_len(unsigned int len);
> void emac_rx_timestamp(struct prueth_emac *emac,
> struct sk_buff *skb, u32 *psdata);
> enum netdev_tx icssg_ndo_start_xmit(struct sk_buff *skb, struct net_device *ndev);
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth_sr1.c b/drivers/net/ethernet/ti/icssg/icssg_prueth_sr1.c
> index 64a19ff39562..aeeb8a50376b 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_prueth_sr1.c
> +++ b/drivers/net/ethernet/ti/icssg/icssg_prueth_sr1.c
> @@ -274,10 +274,12 @@ static struct sk_buff *prueth_process_rx_mgm(struct prueth_emac *emac,
> struct prueth_rx_chn *rx_chn = &emac->rx_mgm_chn;
> struct net_device *ndev = emac->ndev;
> struct cppi5_host_desc_t *desc_rx;
> - struct sk_buff *skb, *new_skb;
> + struct page *page, *new_page;
> dma_addr_t desc_dma, buf_dma;
> u32 buf_dma_len, pkt_len;
> + struct sk_buff *skb;
Can we get rid of SKB entirely from the management channel code?
The packet received on this channel is never passed to user space so
I don't see why SKB is required.
> void **swdata;
> + void *pa;
> int ret;
>
> ret = k3_udma_glue_pop_rx_chn(rx_chn->rx_chn, flow_id, &desc_dma);
> @@ -299,32 +301,35 @@ static struct sk_buff *prueth_process_rx_mgm(struct prueth_emac *emac,
> }
>
> swdata = cppi5_hdesc_get_swdata(desc_rx);
> - skb = *swdata;
> + page = *swdata;
> cppi5_hdesc_get_obuf(desc_rx, &buf_dma, &buf_dma_len);
> pkt_len = cppi5_hdesc_get_pktlen(desc_rx);
>
> dma_unmap_single(rx_chn->dma_dev, buf_dma, buf_dma_len, DMA_FROM_DEVICE);
> k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
>
> - new_skb = netdev_alloc_skb_ip_align(ndev, PRUETH_MAX_PKT_SIZE);
> + new_page = page_pool_dev_alloc_pages(rx_chn->pg_pool);
> /* if allocation fails we drop the packet but push the
> * descriptor back to the ring with old skb to prevent a stall
> */
> - if (!new_skb) {
> + if (!new_page) {
> netdev_err(ndev,
> - "skb alloc failed, dropped mgm pkt from flow %d\n",
> + "page alloc failed, dropped mgm pkt from flow %d\n",
> flow_id);
> - new_skb = skb;
> + new_page = page;
> skb = NULL; /* return NULL */
> } else {
> /* return the filled skb */
> + pa = page_address(page);
> + skb = napi_build_skb(pa, PAGE_SIZE);
> skb_put(skb, pkt_len);
> }
>
> /* queue another DMA */
> - ret = prueth_dma_rx_push(emac, new_skb, &emac->rx_mgm_chn);
> + ret = prueth_dma_rx_push_mapped(emac, &emac->rx_chns, new_page,
> + PRUETH_MAX_PKT_SIZE);
> if (WARN_ON(ret < 0))
> - dev_kfree_skb_any(new_skb);
> + page_pool_recycle_direct(rx_chn->pg_pool, new_page);
>
> return skb;
> }
--
cheers,
-roger
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