From mboxrd@z Thu Jan  1 00:00:00 1970
From: florian.vaussard@epfl.ch (Florian Vaussard)
Date: Wed, 26 Feb 2014 11:31:45 +0100
Subject: TWL6040 fails to initialize
In-Reply-To: <530DC1D3.8040800@ti.com>
References: <530C70B3.4010103@epfl.ch> <530CA8DA.8050806@ti.com>
 <530CB9C6.60806@epfl.ch> <530D972F.805@ti.com> <530DB97E.80309@epfl.ch>
 <530DC1D3.8040800@ti.com>
Message-ID: <530DC291.2060708@epfl.ch>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 02/26/2014 11:28 AM, Peter Ujfalusi wrote:
> On 02/26/2014 11:53 AM, Florian Vaussard wrote:
>> On 02/26/2014 08:26 AM, Peter Ujfalusi wrote:
>>> On 02/25/2014 05:41 PM, Florian Vaussard wrote:
>>>> If the power was not enabled at all, I would be unable to read the
>>>> revision register, no? And delaying the probe by one millisecond would
>>>> be of no help in this case IMHO.
>>>
>>> One thing which might cause this is that if the audpwron GPIO is set high
>>> before the twl6040 module is probing. When I request the GPIO I ask it to be
>>> set to low. If the line was high before this means we initiate the power off
>>> sequence.
>>> Can you try something like this:
>>>
>>
>> I statistically checked that the sleep should be placed after the GPIO
>> request, so indeed this seems to be the problem, and your explanation is
>> plausible. Can you send a proper patch?
>>
>> Now, related to this, I managed to found a part of the datasheet on the
>> Great Internet. Looking at the "Power-Up Sequence" section, it is written:
>>
>> - NRESPWRON goes high -> plug detect and GPO are available
>> - V2V1 goes high -> hook-detect available by I2C programming (sleep mode)
>> - AUDPWRON goes high && READYINT -> ready to communicate through I2C and PDM
>>
>> So, although there seems to be some contradictions on when it is
>> possible to access the I2C, shouldn't we enable the AUDPWRON GPIO
>> _before_ making any I2C access?
>>
>> For the twl6040_probe, the following path would seem more correct to me:
>>
>> 1) enable regulators
>> 2) request AUDPWRON
>> 3) twl6040_power(ON) && regcache_cache_only(false)
>> 4) wait for READYINT (or sleep if deterministic)
>> 5) perform all required I2C accesses (read revision, etc.)
>> 6) twl6040_power(OFF) && regcache_cache_only(true)
>>
>> What do you think?
> 
> Even when the AUDPWRON signal is low we can access to registers in VIO domain,
> plug detect and GPO functions. So there's no need to power on the codec just
> to power it down later.
> 

Ok, if it is safe to do so, I am fine with the current probe. I let you
post a patch to add a delay after requesting the GPIO.

Regards,
Florian

> 
>> Thanks,
>> Florian
>>
>>> diff --git a/drivers/mfd/twl6040.c b/drivers/mfd/twl6040.c
>>> index 75316fb33448..d2a0bd1539ae 100644
>>> --- a/drivers/mfd/twl6040.c
>>> +++ b/drivers/mfd/twl6040.c
>>> @@ -674,6 +674,9 @@ static int twl6040_probe(struct i2c_client *client,
>>>                                             GPIOF_OUT_INIT_LOW, "audpwron");
>>>                 if (ret)
>>>                         goto gpio_err;
>>> +
>>> +               /* power-down sequence latency */
>>> +               usleep_range(500, 700);
>>>         }
>>>
>>>         ret = regmap_add_irq_chip(twl6040->regmap, twl6040->irq, IRQF_ONESHOT,
>>>
>>>
> 
>