Re: [PATCH 4/4] mmc: pwrseq-simple: add disable-post-power-on option

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On Tue, Dec 13, 2016 at 12:01 AM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> On 9 December 2016 at 19:09, Rob Herring <robh@xxxxxxxxxx> wrote:
>> On Fri, Dec 02, 2016 at 01:06:47AM -0800, Matt Ranostay wrote:
>>> On Fri, Dec 2, 2016 at 12:28 AM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>>> > On 2 December 2016 at 08:22, Matt Ranostay <matt@ranostay.consulting> wrote:
>>> >>
>>> >>
>>> >>> On Dec 1, 2016, at 23:13, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>>> >>>
>>> >>>> On 2 December 2016 at 07:17, Matt Ranostay <matt@ranostay.consulting> wrote:
>>> >>>> Add optional device-post-power-on parameters to disable post_power_on
>>> >>>> function from being called since this breaks some device.
>>> >>>>
>>> >>>> Cc: Tony Lindgren <tony@xxxxxxxxxxx>
>>> >>>> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>>> >>>> Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
>>> >>>> ---
>>> >>>> Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.txt | 2 ++
>>> >>>> drivers/mmc/core/pwrseq_simple.c                            | 7 +++++++
>>> >>>> 2 files changed, 9 insertions(+)
>>> >>>>
>>> >>>> diff --git a/Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.txt b/Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.txt
>>> >>>> index bea306d772d1..09fa153f743e 100644
>>> >>>> --- a/Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.txt
>>> >>>> +++ b/Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.txt
>>> >>>> @@ -24,6 +24,8 @@ Optional properties:
>>> >>>>        de-asserting the reset-gpios (if any)
>>> >>>> - invert-off-state: Invert the power down state for the reset-gpios (if any)
>>> >>>>        and pwrdn-gpios (if any)
>>> >>>> +- disable-post-power-on : Avoid post_power_on function from being called since
>>> >>>> +       this breaks some devices
>>> >>>
>>> >>> This is a bit weird. I would like to avoid this, if possible.
>>> >>>
>>> >>> Perhaps if you simply describe the sequence in detail for your device
>>> >>> we can figure out the best option together.
>>> >>
>>> >> Yeah I know it is a bit weird but we need to keep that reset pin high for at least some time after pre power on.   So any case it would be another property
>>> >
>>> > This went offlist, please resend.
>>> >
>>> > Moreover, please try to describe the sequence you need in detail
>>> > according to your HW spec.
>>> >
>>>
>>> Yeah oops....
>>>
>>> So basically we need to drive the reset and powerdown lines high with
>>> a 300 milliseconds delay between both...
>>> can't have the reset line low with post power on (pretty sure but
>>> would need a delay anyway), and we need both reset + powerdown line
>>> set low on powerdown.
>>>
>>> So the power down sequence would need to be reversed for this
>>> application in pwrseq-simple.
>>
>> This sounds like you need a device specific sequence to me. Otherwise,
>> write a language to describe any power control waveforms rather than
>> trying to bolt on more and more properties. (Don't really go write a
>> language.)
>
> Actually this isn't so device specific. The cw1200 wifi chip which is
> being used with ux500 SoCs has a very similar sequence. Allow me to
> check the details and get back.

Ok. It would be good to have something common than a bunch of one-off
solutions for sure.

>
> Anyway, my point is that I think we can figure out a common sequence
> to support these kind required sequences. That is to me preferred over
> adding a new (two to support cw1200) device specific pwrseq driver.
>
> Kind regards
> Uffe
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