net: netsec: Sync dma for device on buffer allocation

Message ID 1562249469-14807-1-git-send-email-ilias.apalodimas@linaro.org
State Superseded
Headers show
Series
  • net: netsec: Sync dma for device on buffer allocation
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Commit Message

Ilias Apalodimas July 4, 2019, 2:11 p.m.
Quoting Arnd,

We have to do a sync_single_for_device /somewhere/ before the
buffer is given to the device. On a non-cache-coherent machine with
a write-back cache, there may be dirty cache lines that get written back
after the device DMA's data into it (e.g. from a previous memset
from before the buffer got freed), so you absolutely need to flush any
dirty cache lines on it first.

Since the coherency is configurable in this device make sure we cover
all configurations by explicitly syncing the allocated buffer for the
device before refilling it's descriptors

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

---
 drivers/net/ethernet/socionext/netsec.c | 5 +++++
 1 file changed, 5 insertions(+)

-- 
2.20.1

Comments

David Miller July 5, 2019, 10:42 p.m. | #1
From: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Date: Thu,  4 Jul 2019 17:11:09 +0300

> Quoting Arnd,

> 

> We have to do a sync_single_for_device /somewhere/ before the

> buffer is given to the device. On a non-cache-coherent machine with

> a write-back cache, there may be dirty cache lines that get written back

> after the device DMA's data into it (e.g. from a previous memset

> from before the buffer got freed), so you absolutely need to flush any

> dirty cache lines on it first.

> 

> Since the coherency is configurable in this device make sure we cover

> all configurations by explicitly syncing the allocated buffer for the

> device before refilling it's descriptors

> 

> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>


Please make it explicit in your Subject lines which tree a patch is
for, in this case it should have been "[PATCH net-next] ".

Applied, thanks.

Patch

diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index 5544a722543f..e05a7191336d 100644
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -727,6 +727,7 @@  static void *netsec_alloc_rx_data(struct netsec_priv *priv,
 {
 
 	struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
+	enum dma_data_direction dma_dir;
 	struct page *page;
 
 	page = page_pool_dev_alloc_pages(dring->page_pool);
@@ -742,6 +743,10 @@  static void *netsec_alloc_rx_data(struct netsec_priv *priv,
 	 * cases and reserve enough space for headroom + skb_shared_info
 	 */
 	*desc_len = PAGE_SIZE - NETSEC_RX_BUF_NON_DATA;
+	dma_dir = page_pool_get_dma_dir(dring->page_pool);
+	dma_sync_single_for_device(priv->dev,
+				   *dma_handle - NETSEC_RXBUF_HEADROOM,
+				   PAGE_SIZE, dma_dir);
 
 	return page_address(page);
 }