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

[Antti Palosaari <crope@iki.fi>]

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.

I have 3 mn88472 and 1 mn88473 device and all those seems to work fine 
for me. I don't care to buy anymore devices to find out one which does 
not work. Somehow root of cause should be find - it is not proper fix to 
repeat or break I2C messages to multiple smaller ones.

Antti

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