Re: [PATCH v2] wifi: ath10k: Delay the unmapping of the buffer

[Kalle Valo]

Youghandhar Chintala <quic_youghand@xxxxxxxxxxx> wrote:

> On WCN3990, we are seeing a rare scenario where copy engine hardware is
> sending a copy complete interrupt to the host driver while still
> processing the buffer that the driver has sent, this is leading into an
> SMMU fault triggering kernel panic. This is happening on copy engine
> channel 3 (CE3) where the driver normally enqueues WMI commands to the
> firmware. Upon receiving a copy complete interrupt, host driver will
> immediately unmap and frees the buffer presuming that hardware has
> processed the buffer. In the issue case, upon receiving copy complete
> interrupt, host driver will unmap and free the buffer but since hardware
> is still accessing the buffer (which in this case got unmapped in
> parallel), SMMU hardware will trigger an SMMU fault resulting in a
> kernel panic.
> 
> In order to avoid this, as a work around, add a delay before unmapping
> the copy engine source DMA buffer. This is conditionally done for
> WCN3990 and only for the CE3 channel where issue is seen.
> 
> Below is the crash signature:
> 
> wifi smmu error: kernel: [ 10.120965] arm-smmu 15000000.iommu: Unhandled
> context fault: fsr=0x402, iova=0x7fdfd8ac0,
> fsynr=0x500003,cbfrsynra=0xc1, cb=6 arm-smmu 15000000.iommu: Unhandled
> context fault:fsr=0x402, iova=0x7fe06fdc0, fsynr=0x710003,
> cbfrsynra=0xc1, cb=6 qcom-q6v5-mss 4080000.remoteproc: fatal error
> received: err_qdi.c:1040:EF:wlan_process:0x1:WLAN RT:0x2091:
> cmnos_thread.c:3998:Asserted in copy_engine.c:AXI_ERROR_DETECTED:2149
> remoteproc remoteproc0: crash detected in
> 4080000.remoteproc: type fatal error <3> remoteproc remoteproc0:
> handling crash #1 in 4080000.remoteproc
> 
> pc : __arm_lpae_unmap+0x500/0x514
> lr : __arm_lpae_unmap+0x4bc/0x514
> sp : ffffffc011ffb530
> x29: ffffffc011ffb590 x28: 0000000000000000
> x27: 0000000000000000 x26: 0000000000000004
> x25: 0000000000000003 x24: ffffffc011ffb890
> x23: ffffffa762ef9be0 x22: ffffffa77244ef00
> x21: 0000000000000009 x20: 00000007fff7c000
> x19: 0000000000000003 x18: 0000000000000000
> x17: 0000000000000004 x16: ffffffd7a357d9f0
> x15: 0000000000000000 x14: 00fd5d4fa7ffffff
> x13: 000000000000000e x12: 0000000000000000
> x11: 00000000ffffffff x10: 00000000fffffe00
> x9 : 000000000000017c x8 : 000000000000000c
> x7 : 0000000000000000 x6 : ffffffa762ef9000
> x5 : 0000000000000003 x4 : 0000000000000004
> x3 : 0000000000001000 x2 : 00000007fff7c000
> x1 : ffffffc011ffb890 x0 : 0000000000000000 Call trace:
> __arm_lpae_unmap+0x500/0x514
> __arm_lpae_unmap+0x4bc/0x514
> __arm_lpae_unmap+0x4bc/0x514
> arm_lpae_unmap_pages+0x78/0xa4
> arm_smmu_unmap_pages+0x78/0x104
> __iommu_unmap+0xc8/0x1e4
> iommu_unmap_fast+0x38/0x48
> __iommu_dma_unmap+0x84/0x104
> iommu_dma_free+0x34/0x50
> dma_free_attrs+0xa4/0xd0
> ath10k_htt_rx_free+0xc4/0xf4 [ath10k_core] ath10k_core_stop+0x64/0x7c
> [ath10k_core]
> ath10k_halt+0x11c/0x180 [ath10k_core]
> ath10k_stop+0x54/0x94 [ath10k_core]
> drv_stop+0x48/0x1c8 [mac80211]
> ieee80211_do_open+0x638/0x77c [mac80211] ieee80211_open+0x48/0x5c
> [mac80211]
> __dev_open+0xb4/0x174
> __dev_change_flags+0xc4/0x1dc
> dev_change_flags+0x3c/0x7c
> devinet_ioctl+0x2b4/0x580
> inet_ioctl+0xb0/0x1b4
> sock_do_ioctl+0x4c/0x16c
> compat_ifreq_ioctl+0x1cc/0x35c
> compat_sock_ioctl+0x110/0x2ac
> __arm64_compat_sys_ioctl+0xf4/0x3e0
> el0_svc_common+0xb4/0x17c
> el0_svc_compat_handler+0x2c/0x58
> el0_svc_compat+0x8/0x2c
> 
> Tested-on: WCN3990 hw1.0 SNOC WLAN.HL.2.0-01387-QCAHLSWMTPLZ-1
> 
> Tested-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> Signed-off-by: Youghandhar Chintala <quic_youghand@xxxxxxxxxxx>
> Signed-off-by: Kalle Valo <quic_kvalo@xxxxxxxxxxx>

Patch applied to ath-next branch of ath.git, thanks.

acd4324e5f1f wifi: ath10k: Delay the unmapping of the buffer

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20221012142733.32420-1-quic_youghand@xxxxxxxxxxx/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches