netdev - [PATCH net-next v8 5/8] page_pool: add DMA-sync-for-CPU inline helper

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Message-ID: <20240308141833.2966600-6-aleksander.lobakin@intel.com>
Date: Fri,  8 Mar 2024 15:18:30 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
	Alexander Duyck <alexanderduyck@...com>,
	Yunsheng Lin <linyunsheng@...wei.com>,
	David Christensen <drc@...ux.vnet.ibm.com>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Paul Menzel <pmenzel@...gen.mpg.de>,
	nex.sw.ncis.osdt.itp.upstreaming@...el.com,
	netdev@...r.kernel.org,
	intel-wired-lan@...ts.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net-next v8 5/8] page_pool: add DMA-sync-for-CPU inline helper

Each driver is responsible for syncing buffers written by HW for CPU
before accessing them. Almost each PP-enabled driver uses the same
pattern, which could be shorthanded into a static inline to make driver
code a little bit more compact.
Introduce a simple helper which performs DMA synchronization for the
size passed from the driver. It can be used even when the pool doesn't
manage DMA-syncs-for-device, just make sure the page has a correct DMA
address set via page_pool_set_dma_addr().

Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
 include/net/page_pool/helpers.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index c7bb06750e85..873631c79ab1 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -52,6 +52,8 @@
 #ifndef _NET_PAGE_POOL_HELPERS_H
 #define _NET_PAGE_POOL_HELPERS_H
 
+#include <linux/dma-mapping.h>
+
 #include <net/page_pool/types.h>
 
 #ifdef CONFIG_PAGE_POOL_STATS
@@ -395,6 +397,28 @@ static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
 	return false;
 }
 
+/**
+ * page_pool_dma_sync_for_cpu - sync Rx page for CPU after it's written by HW
+ * @pool: &page_pool the @page belongs to
+ * @page: page to sync
+ * @offset: offset from page start to "hard" start if using PP frags
+ * @dma_sync_size: size of the data written to the page
+ *
+ * Can be used as a shorthand to sync Rx pages before accessing them in the
+ * driver. Caller must ensure the pool was created with ``PP_FLAG_DMA_MAP``.
+ * Note that this version performs DMA sync unconditionally, even if the
+ * associated PP doesn't perform sync-for-device.
+ */
+static inline void page_pool_dma_sync_for_cpu(const struct page_pool *pool,
+					      const struct page *page,
+					      u32 offset, u32 dma_sync_size)
+{
+	dma_sync_single_range_for_cpu(pool->p.dev,
+				      page_pool_get_dma_addr(page),
+				      offset + pool->p.offset, dma_sync_size,
+				      page_pool_get_dma_dir(pool));
+}
+
 static inline bool page_pool_put(struct page_pool *pool)
 {
 	return refcount_dec_and_test(&pool->user_cnt);
-- 
2.44.0