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Date:   Wed, 9 Sep 2020 02:04:46 +0000
From:   Zhi Chen <zhichen@codeaurora.org>
To:     Ben Greear <greearb@candelatech.com>
Cc:     ath10k@lists.infradead.org, linux-wireless@vger.kernel.org
Subject: Re: [PATCH,v4] Revert "ath10k: fix DMA related firmware crashes on
 multiple devices"
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Hi Ben,
   Thanks for your information. The DMA issue is host related. We never 
hit this issue with X86 platform. And it was only seen in stress cases 
with 50+ STAs(association and disassociation repeatedly). What's the 
host platform you are using? And how was the issue reproduced?

Thanks,
Zhi

On 2020-09-09 01:48, Ben Greear wrote:
> Hello,
> 
> Just FYI:  I added this patch to my ath10k-ct driver, and a user
> reported it causes
> regressions on his particular 9888 system when using ath10k-ct wave-2 
> firmware:
> 
> [   21.204868] ath10k_pci 0000:00:00.0: qca9888 hw2.0 target
> 0x01000000 chip_id 0x00000000 sub 0000:0000
> [   21.214437] ath10k_pci 0000:00:00.0: kconfig debug 0 debugfs 1
> tracing 0 dfs 1 testmode 0
> [   21.233298] ath10k_pci 0000:00:00.0: firmware ver
> 10.4b-ct-9888-tH-13-8c5b2baa2 api 5 features
> mfp,peer-flow-ctrl,txstatus-noack,wmi-10.x-CT,ratemask-CT,regdump-CT,txrate-CT,flush-all-CT,pingpong-CT,ch-regs-CT,nop-CT,htt-mgt-CT,set-special-CT,no-bmiss-CT,tx-rc-CT,cust-stats-CT,txrate2-CT,beacon-cb-CT,wmi-block-ack-CT,wmi-bcn-rc-CT
> crc32 a00b5f36
> [   21.596684] ath10k_pci 0000:00:00.0: board_file api 2 bmi_id 0:20
> crc32 5bb32c02[   23.546156] ath10k_pci 0000:00:00.0: unsupported HTC
> service id: 1536
> 
> I'll revert this for the 9888 chipset (at least) in my driver,
> possibly you need to do similar.
> 
> https://github.com/greearb/ath10k-ct/issues/153
> 
> Thanks,
> Ben
> 
> On 1/13/20 8:35 PM, Zhi Chen wrote:
>> This reverts commit 76d164f582150fd0259ec0fcbc485470bcd8033e.
>> PCIe hung issue was observed on multiple platforms. The issue was 
>> reproduced
>> when DUT was configured as AP and associated with 50+ STAs.
>> 
>> For QCA9984/QCA9888, the DMA_BURST_SIZE register controls the AXI 
>> burst size
>> of the RD/WR access to the HOST MEM.
>> 0 - No split , RAW read/write transfer size from MAC is put out on bus
>>      as burst length
>> 1 - Split at 256 byte boundary
>> 2,3 - Reserved
>> 
>> With PCIe protocol analyzer, we can see DMA Read crossing 4KB boundary 
>> when
>> issue happened. It broke PCIe spec and caused PCIe stuck. So revert
>> the default value from 0 to 1.
>> 
>> Tested:  IPQ8064 + QCA9984 with firmware 10.4-3.10-00047
>>           QCS404 + QCA9984 with firmware 10.4-3.9.0.2--00044
>>           Synaptics AS370 + QCA9888  with firmware 10.4-3.9.0.2--00040
>> 
>> Signed-off-by: Zhi Chen <zhichen@codeaurora.org>
>> ---
>> v2: restored 10.2 register configuration
>> v3: modified commit message
>> v4: resolved conflicts
>> ---
>>   drivers/net/wireless/ath/ath10k/hw.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/net/wireless/ath/ath10k/hw.h 
>> b/drivers/net/wireless/ath/ath10k/hw.h
>> index 21b7a2a..775fd62 100644
>> --- a/drivers/net/wireless/ath/ath10k/hw.h
>> +++ b/drivers/net/wireless/ath/ath10k/hw.h
>> @@ -816,7 +816,7 @@ ath10k_is_rssi_enable(struct ath10k_hw_params *hw,
>>     #define TARGET_10_4_TX_DBG_LOG_SIZE		1024
>>   #define TARGET_10_4_NUM_WDS_ENTRIES		32
>> -#define TARGET_10_4_DMA_BURST_SIZE		0
>> +#define TARGET_10_4_DMA_BURST_SIZE		1
>>   #define TARGET_10_4_MAC_AGGR_DELIM		0
>>   #define TARGET_10_4_RX_SKIP_DEFRAG_TIMEOUT_DUP_DETECTION_CHECK 1
>>   #define TARGET_10_4_VOW_CONFIG			0
>>