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Date:   Fri, 11 Feb 2022 14:02:56 +0100
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Subject: Re: Possible bug on wilc1000 [Klartext]
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To:     Ajay.Kathat@microchip.com, cniedermaier@dh-electronics.com,
        linux-wireless@vger.kernel.org
Cc:     Claudiu.Beznea@microchip.com, Tudor.Ambarus@microchip.com,
        ageisreiter@dh-electronics.com
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From:   Marek Vasut <marex@denx.de>
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On 2/11/22 12:23, Ajay.Kathat@microchip.com wrote:
> On 11/02/22 15:59, Marek Vasut wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know
>> the content is safe
>>
>> On 2/11/22 11:15, Ajay.Kathat@microchip.com wrote:
>>> On 10/02/22 21:55, Marek Vasut wrote:
>>>>
>>>> On 2/10/22 17:19, Ajay.Kathat@microchip.com wrote:
>>>>
>>>> Hi,
>>>>
>>>>> On 10/02/22 14:10, Christoph Niedermaier wrote:
>>>>>> From: Ajay.Kathat@microchip.com [mailto:Ajay.Kathat@microchip.com]
>>>>>> Sent: Wednesday, February 9, 2022 3:37 PM
>>>>>>> On 08/02/22 21:56, Christoph Niedermaier wrote:
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> I tested the wireless chip wilc1000 with the 5.16.5 Kernel and the
>>>>>>>> firmware v15.4.1
>>>>>>>> (https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/atmel/wilc1000_wifi_firmware-1.bin)
>>>>>>>>
>>>>>>>>
>>>>>>>> on an i.MX6 QUAD with iperf3:
>>>>>>>>
>>>>>>>> # iperf3 -c IP_ADDR -P 16 -t 0
>>>>>>>>
>>>>>>>> After a while the test gets stuck and I got the following kernel
>>>>>>>> messages:
>>>>>>>> mmc0: Timeout waiting for hardware interrupt.
>>>>>>>> mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
>>>>>>>> mmc0: sdhci: Sys addr:  0x138f0200 | Version: 0x00000002
>>>>>>>> mmc0: sdhci: Blk size:  0x00000158 | Blk cnt: 0x00000001
>>>>>>>> mmc0: sdhci: Argument:  0x14000158 | Trn mode: 0x00000013
>>>>>>>> mmc0: sdhci: Present:   0x01d88a0a | Host ctl: 0x00000013
>>>>>>>> mmc0: sdhci: Power:     0x00000002 | Blk gap: 0x00000080
>>>>>>>> mmc0: sdhci: Wake-up:   0x00000008 | Clock: 0x0000009f
>>>>>>>> mmc0: sdhci: Timeout:   0x0000008f | Int stat: 0x00000000
>>>>>>>> mmc0: sdhci: Int enab:  0x107f100b | Sig enab: 0x107f100b
>>>>>>>> mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000003
>>>>>>>> mmc0: sdhci: Caps:      0x07eb0000 | Caps_1: 0x0000a000
>>>>>>>> mmc0: sdhci: Cmd:       0x0000353a | Max curr: 0x00ffffff
>>>>>>>> mmc0: sdhci: Resp[0]:   0x00001000 | Resp[1]: 0x00000000
>>>>>>>> mmc0: sdhci: Resp[2]:   0x00000000 | Resp[3]: 0x00000000
>>>>>>>> mmc0: sdhci: Host ctl2: 0x00000000
>>>>>>>> mmc0: sdhci: ADMA Err:  0x00000007 | ADMA Ptr: 0x4c041200
>>>>>>>> mmc0: sdhci-esdhc-imx: ========= ESDHC IMX DEBUG STATUS DUMP
>>>>>>>> =========
>>>>>>>> mmc0: sdhci-esdhc-imx: cmd debug status:  0x2100
>>>>>>>> mmc0: sdhci-esdhc-imx: data debug status:  0x2200
>>>>>>>> mmc0: sdhci-esdhc-imx: trans debug status:  0x2300
>>>>>>>> mmc0: sdhci-esdhc-imx: dma debug status:  0x2402
>>>>>>>> mmc0: sdhci-esdhc-imx: adma debug status:  0x25b4
>>>>>>>> mmc0: sdhci-esdhc-imx: fifo debug status:  0x2610
>>>>>>>> mmc0: sdhci-esdhc-imx: async fifo debug status: 0x2751
>>>>>>>> mmc0: sdhci: ============================================
>>>>>>>> wilc1000_sdio mmc0:0001:1: wilc_sdio_cmd53..failed, err(-110)
>>>>>>>> wilc1000_sdio mmc0:0001:1: Failed cmd53 [0], bytes read...
>>>>>>>>
>>>>>>>> I tried to reduce the clock speed to 20MHz in the devicetree with
>>>>>>>> max-frequency = <20000000>;
>>>>>>>> but the problem then also occurs.
>>>>>>>>
>>>>>>>> Is this a possible bug?
>>>>>>>>
>>>>>>>>
>>>>>> Hi Ajay,
>>>>>> Thanks for the answer.
>>>>>>
>>>>>>> The bus error seems to be specific to the host during the SDIO
>>>>>>> transfer.
>>>>>>> How long does it take to reproduce it? Does the issue also happen
>>>>>>> without "-P 16" iPerf3 option?
>>>>>> It takes about 10s (something a bit longer) till I got this kernel
>>>>>> error
>>>>>> messages and it doesn't matter if I use it with "-P 16" or without.
>>>>>
>>>>>
>>>>> I did not observe the issue with my setup(SAMA5D4 XPLAINED + WILC1000
>>>>> SDIO) when tested iPerf for a longer duration(~1000sec). I suspect the
>>>>> issue could be related to the SDHCI host controller.
>>>>> Try to debug the host controller side for the possible cause of
>>>>> timeout.
>>>>
>>>> It seems the timeout happens because the card fails to respond to SDIO
>>>> command 53, right ?
>>>>
>>>
>>> Yes, the timeout could be for any reason like either the CMD53 has not
>>> reached to chip or response not received correctly at host end.
>>
>> The problem happens seconds or tens of seconds into the test, so there
>> must've been CMD53 which reached the card before the problem occurred,
>> and there must have been a lot of those CMD53 before the problem
>> happened too, since CMD53 seems to be some data transfer CMD ?
>>
>>>> Is there some error logging/tracing functionality in the WILC1000
>>>> firmware which can provide further information why the card did not
>>>> respond ?
>>>
>>>
>>> WILC1000 SD module has UART serial debug port for firmware logs but I
>>> don't think it would be useful here because it needs to be debug/probe
>>> at SDIO bus level.
>>
>> Is there some other kind of logging which can tell us more details on
>> where to look for this problem ?
>>
>> Maybe we can try monitoring the SDIO traffic with ftrace ?
>>
>> Any other options, short of taking the hardware apart ?
>>
>>>> Could it be the card suffered some sort of FIFO overflow ? The MX6Q
>>>> is a
>>>> bit more performant than the CA7 (I think?) SAMA5D4, so maybe that
>>>> plays
>>>> some role ?
>>>
>>> As I understand, the issue is observed with basic iPerf testing(less
>>> throughput) so not sure if the host performance will have such an
>>> impact. IIRC few of the customers are using the same host(i.MX6) though
>>> I am not sure if it's over SPI or SDIO bus. Till now, I have not come
>>> across such limitations with the specific host.
>>
>> That iperf -P 16 hammers the chip with a lot of short packets, the
>> problem does not occur during iperf3 -P 1 run or UDP iperf3 run (that's
>> the one with low traffic). Here the interface is saturated, that's why I
>> speculate some sort of FIFO overrun is happening.
>>
> 
> But earlier it was mentioned that the problem doesn't matter with or
> without "-P" option. So it seems the issue happens during stress test.

I missed that one. So apparently multiple parallel streams only make the 
issue happen quicker.

>> I have also noticed there are some wilc1000 downstream drivers with huge
>> stacks of patches, but I never really figured out whether those are
>> still relevant or whether the upstream wilc1000 driver is perfectly
>> fine. I would like to believe it is the later, is it ?
> 
> Yes, wilc1000 mainline driver has all the required changes except few
> minor bug fixes and new features but none related to this scenario.

All right, so we stick with upstream, thanks.