[PATCH 2/2] gianfar: handle map error in gfar_start_xmit()

From: Arseny Solokha
Date: Fri Dec 05 2014 - 05:38:36 EST

From: Arseny Solokha <asolokha@xxxxxxxxxx>

When DMA-API debugging is enabled in the kernel, it spews the following
upon upping the link:

WARNING: at lib/dma-debug.c:1135
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W O 3.18.0-rc7 #1
task: c0720340 ti: effe2000 task.ti: c0750000
NIP: c01d7c1c LR: c01d7c1c CTR: c02250fc
REGS: effe3d40 TRAP: 0700 Tainted: G W O (3.18.0-rc7)
MSR: 00021000 <CE,ME> CR: 22044242 XER: 20000000

GPR00: c01d7c1c effe3df0 c0720340 00000095 c201e404 c201e9f0 00021000 01a9d000
GPR08: 00000007 00000000 01a9d000 00000313 22044242 00583f60 05f41012 00000000
GPR16: 00000000 000000ff 00000000 00000000 00000000 c5dc3b40 c5677720 00000001
GPR24: c0730000 00029000 c0d0d828 c072c394 effe3e48 c075baec c0d0f020 ee31e600
NIP [c01d7c1c] check_unmap+0x5b4/0xae4
LR [c01d7c1c] check_unmap+0x5b4/0xae4
Call Trace:
[effe3df0] [c01d7c1c] check_unmap+0x5b4/0xae4 (unreliable)
[effe3e40] [c01d81c4] debug_dma_unmap_page+0x78/0x8c
[effe3ec0] [c0286ba0] gfar_clean_tx_ring+0x120/0x3c0
[effe3f30] [c0286f90] gfar_poll_tx_sq+0x48/0x94
o[effe3f50] [c030c388] net_rx_action+0x130/0x1ac
[effe3f80] [c00319e0] __do_softirq+0x134/0x240
[effe3fe0] [c0031dd0] irq_exit+0xa4/0xc8
[effe3ff0] [c000e01c] call_do_irq+0x24/0x3c
[c0751e70] [c0004a04] do_IRQ+0x8c/0x108
[c0751e90] [c0010068] ret_from_except+0x0/0x18
--- interrupt: 501 at arch_cpu_idle+0x24/0x5c
LR = arch_cpu_idle+0x24/0x5c
[c0751f50] [c007d2e4] rcu_idle_enter+0xc8/0xcc (unreliable)
[c0751f60] [c006587c] cpu_startup_entry+0x1d4/0x29c
[c0751fb0] [c054399c] start_kernel+0x338/0x34c
[c0751ff0] [c000046c] set_ivor+0x154/0x190
Instruction dump:
394adb30 80fc0018 811c001c 3c60c04f 5529103a 7cca482e 38639e60 813c0020
815c0024 90c10008 4cc63182 48240b01 <0fe00000> 3c60c04f 3863971c 4cc63182
---[ end trace 3eb7bf62ba1b80f9 ]---
Mapped at:
[<c0287420>] gfar_start_xmit+0x424/0x910
[<c030e964>] dev_hard_start_xmit+0x20c/0x3d8
[<c032cc3c>] sch_direct_xmit+0x124/0x22c
[<c030ede8>] __dev_queue_xmit+0x2b8/0x674

Or the following upon starting transmission of some large chunks
of data:

fsl-gianfar ffe25000.ethernet: DMA-API: device driver failed to check map error[device address=0x0000000005fa8000]
------------[ cut here ]------------
WARNING: at lib/dma-debug.c:1135
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Tainted: G O 3.18.0-rc7 #35
task: c071d340 ti: effe2000 task.ti: c074e000
NIP: c01d7c1c LR: c01d7c1c CTR: c022339c
REGS: effe3d40 TRAP: 0700 Tainted: G O (3.18.0-rc7)
MSR: 00021000 <CE,ME> CR: 22044242 XER: 20000000

GPR00: c01d7c1c effe3df0 c071d340 00000094 00000001 c0071750 00000000 00000001
GPR08: 00000000 00000000 effe2000 00000000 20044242 00581f60 05fa8000 000001c4
GPR16: 00000000 000000ff 00000000 000000e4 00000039 c5b1a9c0 c5679c60 00000002
GPR24: c0730000 00029000 c0d0c528 c0729394 effe3e48 c0759aec c0d0d020 ee315900
NIP [c01d7c1c] check_unmap+0x5b4/0xae4
LR [c01d7c1c] check_unmap+0x5b4/0xae4
Call Trace:
[effe3df0] [c01d7c1c] check_unmap+0x5b4/0xae4 (unreliable)
[effe3e40] [c01d81c4] debug_dma_unmap_page+0x78/0x8c
[effe3ec0] [c0284c78] gfar_clean_tx_ring+0x1b4/0x3c0
[effe3f30] [c0284fd4] gfar_poll_tx_sq+0x48/0x94
[effe3f50] [c030a5c4] net_rx_action+0x130/0x1ac
[effe3f80] [c00319e0] __do_softirq+0x134/0x240
[effe3fe0] [c0031dd0] irq_exit+0xa4/0xc8
[effe3ff0] [c000e01c] call_do_irq+0x24/0x3c
[c074fe70] [c0004a04] do_IRQ+0x8c/0x108
[c074fe90] [c0010068] ret_from_except+0x0/0x18
--- interrupt: 501 at arch_cpu_idle+0x24/0x5c
LR = arch_cpu_idle+0x24/0x5c
[c074ff50] [c007d2e4] rcu_idle_enter+0xc8/0xcc (unreliable)
[c074ff60] [c006587c] cpu_startup_entry+0x1d4/0x29c
[c074ffb0] [c054199c] start_kernel+0x338/0x34c
[c074fff0] [c000046c] set_ivor+0x154/0x190
Instruction dump:
394abb30 80fc0018 811c001c 3c60c04e 5529103a 7cca482e 386379f0 813c0020
815c0024 90c10008 4cc63182 4823ed39 <0fe00000> 3c60c04e 386372ac 4cc63182
---[ end trace 008c59ca7ca1f712 ]---
Mapped at:
[<c0285264>] gfar_start_xmit+0x224/0x95c
[<c030cba0>] dev_hard_start_xmit+0x20c/0x3d8
[<c032ae78>] sch_direct_xmit+0x124/0x22c
[<c032b008>] __qdisc_run+0x88/0x1c0
[<c0307920>] net_tx_action+0xf0/0x19c

Ignore these mapping failures in hope we'll have more luck next time.

Signed-off-by: Arseny Solokha <asolokha@xxxxxxxxxx>
---
drivers/net/ethernet/freescale/gianfar.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index f34ca55..9ea887e 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -2296,6 +2296,12 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
0,
frag_len,
DMA_TO_DEVICE);
+ if (unlikely(dma_mapping_error(priv->dev, bufaddr))) {
+ /* As DMA mapping failed, pretend the TX path
+ * is busy to retry later
+ */
+ return NETDEV_TX_BUSY;
+ }

/* set the TxBD length and buffer pointer */
txbdp->bufPtr = bufaddr;
@@ -2345,8 +2351,15 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
fcb->ptp = 1;
}

- txbdp_start->bufPtr = dma_map_single(priv->dev, skb->data,
- skb_headlen(skb), DMA_TO_DEVICE);
+ bufaddr = dma_map_single(priv->dev, skb->data, skb_headlen(skb),
+ DMA_TO_DEVICE);
+ if (unlikely(dma_mapping_error(priv->dev, bufaddr))) {
+ /* As DMA mapping failed, pretend the TX path is busy to retry
+ * later
+ */
+ return NETDEV_TX_BUSY;
+ }
+ txbdp_start->bufPtr = bufaddr;

/* If time stamping is requested one additional TxBD must be set up. The
* first TxBD points to the FCB and must have a data length of
--
2.2.0

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