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Date: Mon, 7 Oct 2019 14:27:57 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc: netdev@...r.kernel.org, davem@...emloft.net,
thomas.petazzoni@...tlin.com, brouer@...hat.com,
lorenzo.bianconi@...hat.com, matteo.croce@...hat.com
Subject: Re: [PATCH 2/7] net: mvneta: introduce page pool API for sw buffer
manager
> Hi Lorenzo,
>
Hi Ilias,
> On Sat, Oct 05, 2019 at 10:44:35PM +0200, Lorenzo Bianconi wrote:
> > Use the page_pool api for allocations and DMA handling instead of
> > __dev_alloc_page()/dma_map_page() and free_page()/dma_unmap_page().
> > Pages are unmapped using page_pool_release_page before packets
> > go into the network stack.
> >
> > The page_pool API offers buffer recycling capabilities for XDP but
> > allocates one page per packet, unless the driver splits and manages
> > the allocated page.
> > This is a preliminary patch to add XDP support to mvneta driver
> >
> > Tested-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> > Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> > drivers/net/ethernet/marvell/Kconfig | 1 +
> > drivers/net/ethernet/marvell/mvneta.c | 76 ++++++++++++++++++++-------
> > 2 files changed, 58 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/marvell/Kconfig b/drivers/net/ethernet/marvell/Kconfig
> > index fb942167ee54..3d5caea096fb 100644
> > --- a/drivers/net/ethernet/marvell/Kconfig
> > +++ b/drivers/net/ethernet/marvell/Kconfig
> > @@ -61,6 +61,7 @@ config MVNETA
> > depends on ARCH_MVEBU || COMPILE_TEST
> > select MVMDIO
> > select PHYLINK
> > + select PAGE_POOL
> > ---help---
> > This driver supports the network interface units in the
> > Marvell ARMADA XP, ARMADA 370, ARMADA 38x and
> > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> > index 128b9fded959..8beae0e1eda7 100644
> > --- a/drivers/net/ethernet/marvell/mvneta.c
> > +++ b/drivers/net/ethernet/marvell/mvneta.c
> > @@ -37,6 +37,7 @@
> > #include <net/ip.h>
> > #include <net/ipv6.h>
> > #include <net/tso.h>
> > +#include <net/page_pool.h>
> >
> > /* Registers */
> > #define MVNETA_RXQ_CONFIG_REG(q) (0x1400 + ((q) << 2))
> > @@ -603,6 +604,10 @@ struct mvneta_rx_queue {
> > u32 pkts_coal;
> > u32 time_coal;
> >
> > + /* page_pool */
> > + struct page_pool *page_pool;
> > + struct xdp_rxq_info xdp_rxq;
> > +
> > /* Virtual address of the RX buffer */
> > void **buf_virt_addr;
> >
> > @@ -1815,19 +1820,12 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
> > dma_addr_t phys_addr;
> > struct page *page;
> >
> > - page = __dev_alloc_page(gfp_mask);
> > + page = page_pool_alloc_pages(rxq->page_pool,
> > + gfp_mask | __GFP_NOWARN);
> > if (!page)
> > return -ENOMEM;
>
> Is the driver syncing the buffer somewhere else? (for_device)
> If not you'll have to do this here.
ack, I will add a dma_sync_to_device() in v2, thx for the hint :)
>
> On a non-cache coherent machine (and i think this one is) you may get dirty
> cache lines handed to the device. Those dirty cache lines might get written back
> *after* the device has DMA'ed it's data. You need to flush those first to avoid
> any data corruption
Right.
Regards,
Lorenzo
>
> >
> > - /* map page for use */
> > - phys_addr = dma_map_page(pp->dev->dev.parent, page, 0, PAGE_SIZE,
> > - DMA_FROM_DEVICE);
> > - if (unlikely(dma_mapping_error(pp->dev->dev.parent, phys_addr))) {
> > - __free_page(page);
> > - return -ENOMEM;
> > - }
> > -
> > - phys_addr += pp->rx_offset_correction;
> > + phys_addr = page_pool_get_dma_addr(page) + pp->rx_offset_correction;
> > mvneta_rx_desc_fill(rx_desc, phys_addr, page, rxq);
> > return 0;
> > }
> > @@ -1894,10 +1892,11 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp,
> > if (!data || !(rx_desc->buf_phys_addr))
> > continue;
> >
> > - dma_unmap_page(pp->dev->dev.parent, rx_desc->buf_phys_addr,
> > - PAGE_SIZE, DMA_FROM_DEVICE);
> > - __free_page(data);
> > + page_pool_put_page(rxq->page_pool, data, false);
> > }
> > + if (xdp_rxq_info_is_reg(&rxq->xdp_rxq))
> > + xdp_rxq_info_unreg(&rxq->xdp_rxq);
> > + page_pool_destroy(rxq->page_pool);
> > }
> >
> > static void
> > @@ -2029,8 +2028,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
> > skb_add_rx_frag(rxq->skb, frag_num, page,
> > frag_offset, frag_size,
> > PAGE_SIZE);
> > - dma_unmap_page(dev->dev.parent, phys_addr,
> > - PAGE_SIZE, DMA_FROM_DEVICE);
> > + page_pool_release_page(rxq->page_pool, page);
> > rxq->left_size -= frag_size;
> > }
> > } else {
> > @@ -2060,9 +2058,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
> > frag_offset, frag_size,
> > PAGE_SIZE);
> >
> > - dma_unmap_page(dev->dev.parent, phys_addr,
> > - PAGE_SIZE, DMA_FROM_DEVICE);
> > -
> > + page_pool_release_page(rxq->page_pool, page);
> > rxq->left_size -= frag_size;
> > }
> > } /* Middle or Last descriptor */
> > @@ -2829,11 +2825,53 @@ static int mvneta_poll(struct napi_struct *napi, int budget)
> > return rx_done;
> > }
> >
> > +static int mvneta_create_page_pool(struct mvneta_port *pp,
> > + struct mvneta_rx_queue *rxq, int size)
> > +{
> > + struct page_pool_params pp_params = {
> > + .order = 0,
> > + .flags = PP_FLAG_DMA_MAP,
> > + .pool_size = size,
> > + .nid = cpu_to_node(0),
> > + .dev = pp->dev->dev.parent,
> > + .dma_dir = DMA_FROM_DEVICE,
> > + };
> > + int err;
> > +
> > + rxq->page_pool = page_pool_create(&pp_params);
> > + if (IS_ERR(rxq->page_pool)) {
> > + err = PTR_ERR(rxq->page_pool);
> > + rxq->page_pool = NULL;
> > + return err;
> > + }
> > +
> > + err = xdp_rxq_info_reg(&rxq->xdp_rxq, pp->dev, 0);
> > + if (err < 0)
> > + goto err_free_pp;
> > +
> > + err = xdp_rxq_info_reg_mem_model(&rxq->xdp_rxq, MEM_TYPE_PAGE_POOL,
> > + rxq->page_pool);
> > + if (err)
> > + goto err_unregister_rxq;
> > +
> > + return 0;
> > +
> > +err_unregister_rxq:
> > + xdp_rxq_info_unreg(&rxq->xdp_rxq);
> > +err_free_pp:
> > + page_pool_destroy(rxq->page_pool);
> > + return err;
> > +}
> > +
> > /* 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)
> > {
> > - int i;
> > + int i, err;
> > +
> > + err = mvneta_create_page_pool(pp, rxq, num);
> > + if (err < 0)
> > + return err;
> >
> > for (i = 0; i < num; i++) {
> > memset(rxq->descs + i, 0, sizeof(struct mvneta_rx_desc));
> > --
> > 2.21.0
> >
>
>
> Thanks
> /Ilias
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