Drivers using Page Pool for Rx buffers do the same pattern on XDP_TX:
syncing-DMA-for-device and obtaining DMA address for &xdp_buff they
are sending.
Add a helper for that to be able to do that in one call in the drivers.
I explicitly added `bool compound` argument and set it to false by
default: only a few drivers, if any, uses high-order pages with Page
Pool, so losing cycles on compound_head() looks suboptimal. Drivers
can always call the underscored version if needed (for example, pass
pool->p.order as the last argument -- will always work).

Signed-off-by: Alexander Lobakin <[email protected]>
---
 include/net/page_pool/helpers.h | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 873631c79ab1..99dc825b03a5 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -397,6 +397,38 @@ static inline bool page_pool_set_dma_addr(struct page 
*page, dma_addr_t addr)
        return false;
 }
 
+static inline dma_addr_t __page_pool_dma_sync_va_for_device(const void *va,
+                                                           u32 dma_sync_size,
+                                                           bool compound)
+{
+       const struct page_pool *pool;
+       const struct page *page;
+       dma_addr_t addr;
+       u32 offset;
+
+       if (unlikely(compound)) {
+               page = virt_to_head_page(va);
+               offset = va - page_address(page);
+       } else {
+               page = virt_to_page(va);
+               offset = offset_in_page(va);
+       }
+
+       addr = page_pool_get_dma_addr(page) + offset;
+       pool = page->pp;
+
+       dma_sync_single_for_device(pool->p.dev, addr, dma_sync_size,
+                                  page_pool_get_dma_dir(pool));
+
+       return addr;
+}
+
+static inline dma_addr_t page_pool_dma_sync_va_for_device(const void *va,
+                                                         u32 dma_sync_size)
+{
+       return __page_pool_dma_sync_va_for_device(va, dma_sync_size, 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
-- 
2.43.0

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