Re: [PATCH 4/7] si2168: Add ts bus coontrol, turn off bus on sleep

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On 2018-01-16 14:38, Antti Palosaari wrote:
> On 01/16/2018 10:14 PM, Brad Love wrote:
>>
>> On 2018-01-16 13:32, Antti Palosaari wrote:
>>> On 01/16/2018 07:31 PM, Brad Love wrote:
>>>>
>>>> On 2018-01-15 23:07, Antti Palosaari wrote:
>>>>> Hello
>>>>> And what is rationale here, is there some use case demod must be
>>>>> active and ts set to tristate (disabled)? Just put demod sleep when
>>>>> you don't use it.
>>>>>
>>>>> regards
>>>>> Antti
>>>>
>>>> Hello Antti,
>>>>
>>>> Perhaps the .ts_bus_ctrl callback does not need to be included in ops,
>>>> but the function is necessary. The demod is already put to sleep when
>>>> not in use, but it leaves the ts bus open. The ts bus has no reason to
>>>> be open when the demod is put to sleep. Leaving the ts bus open during
>>>> sleep affects the other connected demod and nothing is received by it.
>>>> The lgdt3306a driver already tri states its ts bus when put to sleep,
>>>> the si2168 should as well.
>>>
>>> Sounds possible, but unlikely as chip is firmware driven. When you put
>>> chip to sleep you usually want set ts pins to tristate (also other
>>> unused pins) in order to save energy. I haven't never tested it anyway
>>> though, so it could be possible it leaves those pins to some other
>>> state like random output at given time.
>>>
>>> And if you cannot get stream from lgdt3306a, which is connected to
>>> same bus, it really sounds like ts bus pins are left some state
>>> (cannot work if same pin is driven high to other demod whilst other
>>> tries to drive it low.
>>>
>>> Setting ts pins to tri-state during sleep should resolve your issue.
>>
>> Hello Antti,
>>
>> This patch fixes the issue I'm describing, hence why I submitted it. The
>> ts bus must be tristated before putting the chip to sleep for the other
>> demod to get a stream.
>>
>
> I can test tri-state using power meter on some day, but it may be so
> small current that it cannot be seen usb power meter I use (YZXstudio,
> very nice small power meter).
>
> regards
> Antti
>


Nifty looking devices, one just fell into my shopping cart :)

Cheers,

Brad






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