Message-ID: <20130702123717.GA324@hmsreliant.think-freely.org>
Date:	Tue, 2 Jul 2013 08:37:17 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Arend van Spriel <arend@...adcom.com>
Cc:	Larry Finger <Larry.Finger@...inger.net>, linville@...driver.com,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	Stable <stable@...r.kernel.org>,
	Brett Rudley <brudley@...adcom.com>,
	"Franky (Zhenhui) Lin" <frankyl@...adcom.com>,
	Hante Meuleman <meuleman@...adcom.com>,
	brcm80211-dev-list@...adcom.com
Subject: Re: [PATCH] brcmsmac: Fix WARNING caused by lack of calls to
 dma_mapping_error()

On Tue, Jul 02, 2013 at 10:47:13AM +0200, Arend van Spriel wrote:
> On 07/01/2013 11:08 PM, Larry Finger wrote:
> >The driver fails to check the results of DMA mapping in twp places, which results
> >in the following warning:
> >
> >[   28.078515] ------------[ cut here ]------------
> >[   28.078529] WARNING: at lib/dma-debug.c:937 check_unmap+0x47e/0x930()
> >[   28.078533] bcma-pci-bridge 0000:0e:00.0: DMA-API: device driver failed to check map error[device address=0x00000000b5d60d6c] [size=1876 bytes] [mapped as
> >  single]
> >[   28.078536] Modules linked in: bnep bluetooth vboxpci(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) ipv6 b43 brcmsmac rtl8192cu rtl8192c_common rtlwifi mac802
> >11 brcmutil cfg80211 snd_hda_codec_conexant rng_core snd_hda_intel kvm_amd snd_hda_codec ssb kvm mmc_core snd_pcm snd_seq snd_timer snd_seq_device snd k8temp
> >  cordic joydev serio_raw hwmon sr_mod sg pcmcia pcmcia_core soundcore cdrom i2c_nforce2 i2c_core forcedeth bcma snd_page_alloc autofs4 ext4 jbd2 mbcache crc1
> >6 scsi_dh_alua scsi_dh_hp_sw scsi_dh_rdac scsi_dh_emc scsi_dh ata_generic pata_amd
> >[   28.078602] CPU: 1 PID: 2570 Comm: NetworkManager Tainted: G           O 3.10.0-rc7-wl+ #42
> >[   28.078605] Hardware name: Hewlett-Packard HP Pavilion dv2700 Notebook PC/30D6, BIOS F.27 11/27/2008
> >[   28.078607]  0000000000000009 ffff8800bbb03ad8 ffffffff8144f898 ffff8800bbb03b18
> >[   28.078612]  ffffffff8103e1eb 0000000000000002 ffff8800b719f480 ffff8800b7b9c010
> >[   28.078617]  ffffffff824204c0 ffffffff81754d57 0000000000000754 ffff8800bbb03b78
> >[   28.078622] Call Trace:
> >[   28.078624]  <IRQ>  [<ffffffff8144f898>] dump_stack+0x19/0x1b
> >[   28.078634]  [<ffffffff8103e1eb>] warn_slowpath_common+0x6b/0xa0
> >[   28.078638]  [<ffffffff8103e2c1>] warn_slowpath_fmt+0x41/0x50
> >[   28.078650]  [<ffffffff8122d7ae>] check_unmap+0x47e/0x930
> >[   28.078655]  [<ffffffff8122de4c>] debug_dma_unmap_page+0x5c/0x70
> >[   28.078679]  [<ffffffffa04a808c>] dma64_getnextrxp+0x10c/0x190 [brcmsmac]
> >[   28.078691]  [<ffffffffa04a9042>] dma_rx+0x62/0x240 [brcmsmac]
> >[   28.078707]  [<ffffffffa0479101>] brcms_c_dpc+0x211/0x9d0 [brcmsmac]
> >[   28.078717]  [<ffffffffa046d927>] ? brcms_dpc+0x27/0xf0 [brcmsmac]
> >[   28.078731]  [<ffffffffa046d947>] brcms_dpc+0x47/0xf0 [brcmsmac]
> >[   28.078736]  [<ffffffff81047dcc>] tasklet_action+0x6c/0xf0
> >--snip--
> >[   28.078974]  [<ffffffff813891bd>] SyS_sendmsg+0xd/0x20
> >[   28.078979]  [<ffffffff81455c24>] tracesys+0xdd/0xe2
> >[   28.078982] ---[ end trace 6164d1a08148e9c8 ]---
> >[   28.078984] Mapped at:
> >[   28.078985]  [<ffffffff8122c8fd>] debug_dma_map_page+0x9d/0x150
> >[   28.078989]  [<ffffffffa04a9322>] dma_rxfill+0x102/0x3d0 [brcmsmac]
> >[   28.079001]  [<ffffffffa047a13d>] brcms_c_init+0x87d/0x1100 [brcmsmac]
> >[   28.079010]  [<ffffffffa046d851>] brcms_init+0x21/0x30 [brcmsmac]
> >[   28.079018]  [<ffffffffa04786e0>] brcms_c_up+0x150/0x430 [brcmsmac]
> >
> >As the patch adds a new failure mechanism to dma_rxfill(). When I changed the
> >comment at the start of the routine to add that information, I also polished
> >the wording.
> 
> Thanks, Larry
> 
> I think there a bugzilla issue for this that you might want to reference:
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=60261
> 
Thanks Larry, you beat me too it, feel free to reassign the bz to yourself. :)

> >Signed-off-by: Larry Finger <Larry.Finger@...inger.net>
> >Cc: Stable <stable@...r.kernel.org>
> >Cc: Brett Rudley <brudley@...adcom.com>
> >Cc: Arend van Spriel <arend@...adcom.com>
> >Cc: Franky (Zhenhui) Lin <frankyl@...adcom.com>
> >Cc: Hante Meuleman <meuleman@...adcom.com>
> >Cc: brcm80211-dev-list@...adcom.com
> >---
> >
> >  drivers/net/wireless/brcm80211/brcmsmac/dma.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> >diff --git a/drivers/net/wireless/brcm80211/brcmsmac/dma.c b/drivers/net/wireless/brcm80211/brcmsmac/dma.c
> >index 1860c57..6260571 100644
> >--- a/drivers/net/wireless/brcm80211/brcmsmac/dma.c
> >+++ b/drivers/net/wireless/brcm80211/brcmsmac/dma.c
> >@@ -1015,9 +1015,10 @@ static bool dma64_txidle(struct dma_info *di)
> >
> >  /*
> >   * post receive buffers
> >- *  return false is refill failed completely and ring is empty this will stall
> >- *  the rx dma and user might want to call rxfill again asap. This unlikely
> >- *  happens on memory-rich NIC, but often on memory-constrained dongle
> >+ *  return false is refill failed completely or dma mapping failed. The ring
> 
> Missed some polishing opportunity: return false is refill... ->
> return false if refill...
> 
> >+ *  is empty, which will stall the rx dma and user might want to call rxfill
> >+ *  again asap. This is unlikely to happen on a memory-rich NIC, but often on
> >+ *  memory-constrained dongle
> >   */
> >  bool dma_rxfill(struct dma_pub *pub)
> >  {
> >@@ -1078,6 +1079,8 @@ bool dma_rxfill(struct dma_pub *pub)
> >
> >  		pa = dma_map_single(di->dmadev, p->data, di->rxbufsize,
> >  				    DMA_FROM_DEVICE);
> >+		if (dma_mapping_error(di->dmadev,pa))
> >+			return false;
Hmm, wouldn't it be better to set ring_empty to false and break out of the for
loop here, in the event that you partially refilled the ring?  Otherwise, a
single dma mapping failure would let some useable descriptors go unused.

Neil
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