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@xxxxxxxxx>
---
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
