Re: [RFC PATCH] mn88472: reduce firmware download chunk size

[Antti Palosaari <crope@iki.fi>]

On 02/19/2015 08:42 PM, Antti Seppälä wrote:
> On 19 February 2015 at 18:14, Antti Palosaari <crope@iki.fi> wrote:
>> On 02/19/2015 06:01 PM, Antti Seppälä wrote:
>>>
>>> On 19 February 2015 at 17:38, Antti Palosaari <crope@iki.fi> wrote:
>>>>
>>>> On 02/19/2015 12:21 PM, Antti Seppälä wrote:
>>>>>
>>>>> On 19 February 2015 at 11:43, Benjamin Larsson <benjamin@southpole.se>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> On 2015-02-19 10:13, Antti Seppälä wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> It seems that currently the firmware download on the mn88472 is
>>>>>>> somehow wrong for my Astrometa HD-901T2.
>>>>>>>
>>>>>>> Reducing the download chunk size (mn88472_config.i2c_wr_max) to 2
>>>>>>> makes the firmware download consistently succeed.
>>>>>>>
>>>>>>
>>>>>>
>>>>>> Hi, try adding the workaround patch I sent for this.
>>>>>>
>>>>>> [PATCH 1/3] rtl28xxu: lower the rc poll time to mitigate i2c transfer
>>>>>> errors
>>>>>>
>>>>>> I now see that it hasn't been merged. But I have been running with this
>>>>>> patch for a few months now without any major issues.
>>>>>>
>>>>>
>>>>> The patch really did improve firmware loading. Weird...
>>>>>
>>>>> Even with it I still get occasional i2c errors from r820t:
>>>>>
>>>>> [   15.874402] r820t 8-003a: r820t_write: i2c wr failed=-32 reg=0a
>>>>> len=1:
>>>>> da
>>>>> [   81.455517] r820t 8-003a: r820t_read: i2c rd failed=-32 reg=00
>>>>> len=4: 69 74 e6 df
>>>>> [   99.949702] r820t 8-003a: r820t_read: i2c rd failed=-32 reg=00
>>>>> len=4: 69 74 e6 df
>>>>>
>>>>> These errors seem to appear more often if I'm reading the signal
>>>>> strength values using e.g. femon.
>>>>
>>>>
>>>>
>>>> Could you disable whole IR polling and test
>>>> modprobe dvb_usb_v2 disable_rc_polling=1
>>>>
>>>> It is funny that *increasing* RC polling makes things better, though...
>>>>
>>>
>>> Hi.
>>>
>>> I tried loading the driver with polling disabled and it fails completely:
>>>
>>> [ 5526.693563] mn88472 7-0018: downloading firmware from file
>>> 'dvb-demod-mn88472-02.fw'
>>> [ 5527.032209] mn88472 7-0018: firmware download failed=-32
>>> [ 5527.033864] rtl2832 7-0010: i2c reg write failed -32
>>> [ 5527.033874] r820t 8-003a: r820t_write: i2c wr failed=-32 reg=05 len=1:
>>> 83
>>> [ 5527.036014] rtl2832 7-0010: i2c reg write failed -32
>>>
>>> I have no idea why the device behaves so counter-intuitively. Is there
>>> maybe some sorf of internal power-save mode the device enters when
>>> there is no i2c traffic for a while or something?
>>
>>
>> IR polling does not use I2C but some own commands. Could you make more
>> tests. Use rtl28xxu module parameter to disable IR and test. It will disable
>> both IR interrupts and polling. Then make some tests with different IR
>> polling intervals to see how it behaves.
>>
>
> Hi Antti.
>
> I made some further tests for you. Here are the results:
>
> dvb_usb_v2 disable_rc_polling=1: firmware download FAILED
>
> dvb_usb_rtl28xxu disable_rc=1: firmware download FAILED
>
> Then I restored the module parameters to default values and tested
> with various rc->interval values:
>
> interval = 800: firmware download FAILED
> interval = 600: firmware download FAILED
> interval = 400: firmware download FAILED
> interval = 300: firmware download SUCCESS but I2C errors from tuner
> could be sometimes observed
> interval = 200: firmware download SUCCESS
> interval = 100: firmware download SUCCESS
>
> So somehow higher rc polling rate makes the firmware download succeed.
> This could indeed be some locking/timing related bug.
>
> Please let me know if there is something else I can test.

Sure you could do. Play with I2C settings. Test few values to I2C bus 
speed / clock is good start. Put oscilloscope to I2C bus and look what 
there happens on error cases. There is also 2 different I2C commands, 
test if there is any difference. And so. Increasing polling interval to 
something between 250-300 does not sound very bad, though.

regards
Antti

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