[PATCH] mvneta: DMA API misusage fix

[PATCH] mvneta: DMA API misusage fix

[Ezequiel Garcia]

This small patch removes a DMA_API_DEBUG warning, fixing a DMA API misusage.
The change is straightforward: rx DMA mappings are created setting a size
(using some upper-limit buffer size), but destroyed (aka unmapped) setting
the actual data size that was received.

The fix replaces 'data_size' by the MVNETA_RX_BUF_SIZE in the unmap.

I'm not sure how serious this misusage is, so I'd like to ask for advise
about marking this commit for stable. The problem is here since the
introduction of the driver, namely since:

  commit c5aff18204da025fdf714f8f6423372b4b8efd00
  net: mvneta: driver for Marvell Armada 370/XP network unit

Thanks!

Ezequiel Garcia (1):
  net: mvneta: Fix incorrect DMA unmapping size

 drivers/net/ethernet/marvell/mvneta.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
1.8.1.5

[PATCH] net: mvneta: Fix incorrect DMA unmapping size

[Ezequiel Garcia]

The current code unmaps the DMA mapping created for rx skb_buff's by
using the data_size as the the mapping size. This is wrong since the
correct size to specify should match the size used to create the mapping.

This commit removes the following DMA_API_DEBUG warning:

------------[ cut here ]------------
WARNING: at lib/dma-debug.c:887 check_unmap+0x3a8/0x860()
mvneta d0070000.ethernet: DMA-API: device driver frees DMA memory with different size [device address=0x000000002eb80000] [map size=1600 bytes] [unmap size=66 bytes]
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.21-01444-ga88ae13-dirty #92
[<c0013600>] (unwind_backtrace+0x0/0xf8) from [<c0010fb8>] (show_stack+0x10/0x14)
[<c0010fb8>] (show_stack+0x10/0x14) from [<c001afa0>] (warn_slowpath_common+0x48/0x68)
[<c001afa0>] (warn_slowpath_common+0x48/0x68) from [<c001b01c>] (warn_slowpath_fmt+0x30/0x40)
[<c001b01c>] (warn_slowpath_fmt+0x30/0x40) from [<c018d0fc>] (check_unmap+0x3a8/0x860)
[<c018d0fc>] (check_unmap+0x3a8/0x860) from [<c018d734>] (debug_dma_unmap_page+0x64/0x70)
[<c018d734>] (debug_dma_unmap_page+0x64/0x70) from [<c0233f78>] (mvneta_rx+0xec/0x468)
[<c0233f78>] (mvneta_rx+0xec/0x468) from [<c023436c>] (mvneta_poll+0x78/0x16c)
[<c023436c>] (mvneta_poll+0x78/0x16c) from [<c02db468>] (net_rx_action+0x94/0x160)
[<c02db468>] (net_rx_action+0x94/0x160) from [<c0021e68>] (__do_softirq+0xe8/0x1d0)
[<c0021e68>] (__do_softirq+0xe8/0x1d0) from [<c0021ff8>] (do_softirq+0x4c/0x58)
[<c0021ff8>] (do_softirq+0x4c/0x58) from [<c0022228>] (irq_exit+0x58/0x90)
[<c0022228>] (irq_exit+0x58/0x90) from [<c000e7c8>] (handle_IRQ+0x3c/0x94)
[<c000e7c8>] (handle_IRQ+0x3c/0x94) from [<c0008548>] (armada_370_xp_handle_irq+0x4c/0xb4)
[<c0008548>] (armada_370_xp_handle_irq+0x4c/0xb4) from [<c000dc20>] (__irq_svc+0x40/0x50)
Exception stack(0xc04f1f70 to 0xc04f1fb8)
1f60:                                     c1fe46f8 00000000 00001d92 00001d92
1f80: c04f0000 c04f0000 c04f84a4 c03e081c c05220e7 00000001 c05220e7 c04f0000
1fa0: 00000000 c04f1fb8 c000eaf8 c004c048 60000113 ffffffff
[<c000dc20>] (__irq_svc+0x40/0x50) from [<c004c048>] (cpu_startup_entry+0x54/0x128)
[<c004c048>] (cpu_startup_entry+0x54/0x128) from [<c04c1a14>] (start_kernel+0x29c/0x2f0)
[<c04c1a14>] (start_kernel+0x29c/0x2f0) from [<00008074>] (0x8074)
---[ end trace d4955f6acd178110 ]---
Mapped at:
 [<c018d600>] debug_dma_map_page+0x4c/0x11c
 [<c0235d6c>] mvneta_setup_rxqs+0x398/0x598
 [<c0236084>] mvneta_open+0x40/0x17c
 [<c02dbbd4>] __dev_open+0x9c/0x100
 [<c02dbe58>] __dev_change_flags+0x7c/0x134

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
---
 drivers/net/ethernet/marvell/mvneta.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index b8e232b..d5f0d72 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -1378,7 +1378,7 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp,
 
 		dev_kfree_skb_any(skb);
 		dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr,
-				 rx_desc->data_size, DMA_FROM_DEVICE);
+				 MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
 	}
 
 	if (rx_done)
@@ -1424,7 +1424,7 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
 		}
 
 		dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr,
-				 rx_desc->data_size, DMA_FROM_DEVICE);
+				 MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
 
 		rx_bytes = rx_desc->data_size -
 			(ETH_FCS_LEN + MVNETA_MH_SIZE);
-- 
1.8.1.5

Re: [PATCH] net: mvneta: Fix incorrect DMA unmapping size

[David Miller]

From: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Date: Thu,  5 Dec 2013 13:35:37 -0300

> The current code unmaps the DMA mapping created for rx skb_buff's by
> using the data_size as the the mapping size. This is wrong since the
> correct size to specify should match the size used to create the mapping.
> 
> This commit removes the following DMA_API_DEBUG warning:
 ...
> Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>

Applied, thanks.