Re: [PATCH v6 07/15] platform/x86: int3472: Enable I2c daisy chain

Daniel Scally
2021-11-26T12:28:17Z

On 26/11/2021 11:45, Hans de Goede wrote:
> Hi,
>
> On 11/26/21 12:39, Daniel Scally wrote:
>> Hello
>>
>> On 26/11/2021 11:30, Hans de Goede wrote:
>>> Hi,
>>>
>>> On 11/26/21 00:39, Laurent Pinchart wrote:
>>>> Hi Hans,
>>>>
>>>> Thank you for the patch.
>>>>
>>>> On Thu, Nov 25, 2021 at 05:54:04PM +0100, Hans de Goede wrote:
>>>>> From: Daniel Scally <djrscally@gmail.com>
>>>>>
>>>>> The TPS68470 PMIC has an I2C passthrough mode through which I2C traffic
>>>>> can be forwarded to a device connected to the PMIC as though it were
>>>>> connected directly to the system bus. Enable this mode when the chip
>>>>> is initialised.
>>>> Is there any drawback doing this unconditionally, if nothing is
>>>> connected to the bus on the other side (including no pull-ups) ?
>>> I actually never took a really close look at this patch, I just
>>> sorta inherited it from Daniel.
>>>
>>> Now that I have taken a close look, I see that it is setting the
>>> exact same bits as which get set when enabling the VSIO regulator.
>>>
>>> The idea here is that the I2C-passthrough only gets enabled when
>>> the VSIO regulator is turned on, because some sensors end up
>>> shorting the I2C pins to ground when the sensor is not powered.
>>>
>>> Since we set these bits when powering up the VSIO regulator
>>> and since we do that before trying to talk to the sensor
>>> I don't think that we need this (hack) anymore.
>>>
>>> I will give things a try without this change and if things
>>> still work I will drop this patch from the set.
>>>
>>> Daniel, what do you think?
>>
>> Humm, we're only using the VSIO regulator with the VCM though right?
> Nope, there is a mapping from VSIO to dovdd for the ov8865 in the
> board_data; and I'm pretty sure I copied that from your earlier
> attempts at getting regulator lookups registered :)

Oh yeah derp; I was looking at the supply names rather than the
regulator names, my bad!
> And even if the VSIO regulator was only used by the VCM, then it would
> get turned off after probing the VCM, clearing the 2 bits which this
> commit sets. Which would break things if we did not re-enable it when
> the ov8865 needs it.
>
>> Which might not be on when the ov8865 tries to probe. I haven't tried
>> without this patch to be honest; I set it because that was what Windows
>> does when powering on the PMIC.
> See above, I'm pretty sure we can do without this patch which means
> that the INT3472 code will no longer be poking at the PMIC directly
> itself, which is good :)

Yeah, in that case I think you're right and this can be dropped.

> Anyways I'll give this a try sometime next week and then drop the
> patch.

Sounds good

>
> Regards,
>
> Hans
>
>
>
>
>>>>> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
>>>>> Signed-off-by: Daniel Scally <djrscally@gmail.com>
>>>>> ---
>>>>> .../x86/intel/int3472/intel_skl_int3472_tps68470.c | 7 +++++++
>>>>> 1 file changed, 7 insertions(+)
>>>>>
>>>>> diff --git a/drivers/platform/x86/intel/int3472/intel_skl_int3472_tps68470.c b/drivers/platform/x86/intel/int3472/intel_skl_int3472_tps68470.c
>>>>> index c05b4cf502fe..42e688f4cad4 100644
>>>>> --- a/drivers/platform/x86/intel/int3472/intel_skl_int3472_tps68470.c
>>>>> +++ b/drivers/platform/x86/intel/int3472/intel_skl_int3472_tps68470.c
>>>>> @@ -45,6 +45,13 @@ static int tps68470_chip_init(struct device *dev, struct regmap *regmap)
>>>>> return ret;
>>>>> }
>>>>>
>>>>> + /* Enable I2C daisy chain */
>>>>> + ret = regmap_write(regmap, TPS68470_REG_S_I2C_CTL, 0x03);
>>>>> + if (ret) {
>>>>> + dev_err(dev, "Failed to enable i2c daisy chain\n");
>>>>> + return ret;
>>>>> + }
>>>>> +
>>>>> dev_info(dev, "TPS68470 REVID: 0x%02x\n", version);
>>>>>
>>>>> return 0;