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Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for all other voltages

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  Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for  all other voltages Ulf Hansson <ulf.hansson@linaro.org> - 2015-09-14 11:40 +0200
    Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for  all other voltages Vaibhav Hiremath <vaibhav.hiremath@linaro.org> - 2015-09-14 11:50 +0200
      Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for  all other voltages Ulf Hansson <ulf.hansson@linaro.org> - 2015-09-14 12:40 +0200
        Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for  all other voltages Vaibhav Hiremath <vaibhav.hiremath@linaro.org> - 2015-09-14 14:50 +0200
          Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for  all other voltages Vaibhav Hiremath <vaibhav.hiremath@linaro.org> - 2015-09-14 14:50 +0200

#1223977 — Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for all other voltages

[...]

>>>>
>>>> Could this be implemented by regulator API? From patch set 3/3, the
>>>> pxa1928
>>>> voltage_switch hook is to operate the IO pad registers, this seems not
>>>> belong
>>>> to the SDHC IP core.
>>>>
>>>
>>> Not quite sure whether regulator would be right fit for this.
>>
>>
>>  From the patche[3/3], this can be achieved by abstracting the IO PAD as
>> regulators
>> then, we may not need to touch the core sdhci.c. But I'm not sure whether
>> this
>> is the good solution or not.
>
>
> Exactly...
>
>> sdhci Maintainers and experts may have better
>> suggestions.
>>
>
> Thats is the reason I stamped it as a RFC :)
>

[...]

From an mmc core perspective it would be preferred if you implement
this as a regulator (vqmmc).

Especially since we will soon have an API for how to set the I/O
voltages - and the intelligence within that API is not something we
would like to implement for each and every host driver.
https://lkml.org/lkml/2015/8/31/367

Kind regards
Uffe
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#1223989

On Monday 14 September 2015 03:00 PM, Ulf Hansson wrote:
> [...]
>
>>>>>
>>>>> Could this be implemented by regulator API? From patch set 3/3, the
>>>>> pxa1928
>>>>> voltage_switch hook is to operate the IO pad registers, this seems not
>>>>> belong
>>>>> to the SDHC IP core.
>>>>>
>>>>
>>>> Not quite sure whether regulator would be right fit for this.
>>>
>>>
>>>   From the patche[3/3], this can be achieved by abstracting the IO PAD as
>>> regulators
>>> then, we may not need to touch the core sdhci.c. But I'm not sure whether
>>> this
>>> is the good solution or not.
>>
>>
>> Exactly...
>>
>>> sdhci Maintainers and experts may have better
>>> suggestions.
>>>
>>
>> Thats is the reason I stamped it as a RFC :)
>>
>
> [...]
>
>  From an mmc core perspective it would be preferred if you implement
> this as a regulator (vqmmc).
>
> Especially since we will soon have an API for how to set the I/O
> voltages - and the intelligence within that API is not something we
> would like to implement for each and every host driver.
> https://lkml.org/lkml/2015/8/31/367
>


I would still consider this as a regulator specific and may not address
the IO configuration within the SoC which are module specific.
The API regulator_set_voltage_triplet() will not have intelligence to
differentiate whether the call is coming from MMC or somewhere else.

Note that, the IO pad voltage configuration which I am referring to is
MMC specific and applicable only when pad is configured in MMC mode. So
technically it is not simply common pad voltage configuration.


And I am still not sure regulator framework would be right fit for
this. Pinctrl would have been right fit, but...since I saw f_sdh30
driver is already doing this, which is easy fit; so adopted the same.

Thanks,
Vaibhav
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#1224014

On 14 September 2015 at 11:42, Vaibhav Hiremath
<vaibhav.hiremath@linaro.org> wrote:
>
>
> On Monday 14 September 2015 03:00 PM, Ulf Hansson wrote:
>>
>> [...]
>>
>>>>>>
>>>>>> Could this be implemented by regulator API? From patch set 3/3, the
>>>>>> pxa1928
>>>>>> voltage_switch hook is to operate the IO pad registers, this seems not
>>>>>> belong
>>>>>> to the SDHC IP core.
>>>>>>
>>>>>
>>>>> Not quite sure whether regulator would be right fit for this.
>>>>
>>>>
>>>>
>>>>   From the patche[3/3], this can be achieved by abstracting the IO PAD
>>>> as
>>>> regulators
>>>> then, we may not need to touch the core sdhci.c. But I'm not sure
>>>> whether
>>>> this
>>>> is the good solution or not.
>>>
>>>
>>>
>>> Exactly...
>>>
>>>> sdhci Maintainers and experts may have better
>>>> suggestions.
>>>>
>>>
>>> Thats is the reason I stamped it as a RFC :)
>>>
>>
>> [...]
>>
>>  From an mmc core perspective it would be preferred if you implement
>> this as a regulator (vqmmc).
>>
>> Especially since we will soon have an API for how to set the I/O
>> voltages - and the intelligence within that API is not something we
>> would like to implement for each and every host driver.
>> https://lkml.org/lkml/2015/8/31/367
>>
>
>
> I would still consider this as a regulator specific and may not address
> the IO configuration within the SoC which are module specific.
> The API regulator_set_voltage_triplet() will not have intelligence to
> differentiate whether the call is coming from MMC or somewhere else.
>
> Note that, the IO pad voltage configuration which I am referring to is
> MMC specific and applicable only when pad is configured in MMC mode. So
> technically it is not simply common pad voltage configuration.
>
>
> And I am still not sure regulator framework would be right fit for
> this. Pinctrl would have been right fit, but...since I saw f_sdh30
> driver is already doing this, which is easy fit; so adopted the same.

Pinctrl would work as well, or perhaps a combination of both pinctrl
and a regulator.

What I don't like is the solution you have suggested in patch3.

Kind regards
Uffe
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#1224103

On Monday 14 September 2015 04:04 PM, Ulf Hansson wrote:
> On 14 September 2015 at 11:42, Vaibhav Hiremath
> <vaibhav.hiremath@linaro.org> wrote:
>>
>>
>> On Monday 14 September 2015 03:00 PM, Ulf Hansson wrote:
>>>
>>> [...]
>>>
>>>>>>>
>>>>>>> Could this be implemented by regulator API? From patch set 3/3, the
>>>>>>> pxa1928
>>>>>>> voltage_switch hook is to operate the IO pad registers, this seems not
>>>>>>> belong
>>>>>>> to the SDHC IP core.
>>>>>>>
>>>>>>
>>>>>> Not quite sure whether regulator would be right fit for this.
>>>>>
>>>>>
>>>>>
>>>>>    From the patche[3/3], this can be achieved by abstracting the IO PAD
>>>>> as
>>>>> regulators
>>>>> then, we may not need to touch the core sdhci.c. But I'm not sure
>>>>> whether
>>>>> this
>>>>> is the good solution or not.
>>>>
>>>>
>>>>
>>>> Exactly...
>>>>
>>>>> sdhci Maintainers and experts may have better
>>>>> suggestions.
>>>>>
>>>>
>>>> Thats is the reason I stamped it as a RFC :)
>>>>
>>>
>>> [...]
>>>
>>>   From an mmc core perspective it would be preferred if you implement
>>> this as a regulator (vqmmc).
>>>
>>> Especially since we will soon have an API for how to set the I/O
>>> voltages - and the intelligence within that API is not something we
>>> would like to implement for each and every host driver.
>>> https://lkml.org/lkml/2015/8/31/367
>>>
>>
>>
>> I would still consider this as a regulator specific and may not address
>> the IO configuration within the SoC which are module specific.
>> The API regulator_set_voltage_triplet() will not have intelligence to
>> differentiate whether the call is coming from MMC or somewhere else.
>>
>> Note that, the IO pad voltage configuration which I am referring to is
>> MMC specific and applicable only when pad is configured in MMC mode. So
>> technically it is not simply common pad voltage configuration.
>>
>>
>> And I am still not sure regulator framework would be right fit for
>> this. Pinctrl would have been right fit, but...since I saw f_sdh30
>> driver is already doing this, which is easy fit; so adopted the same.
>
> Pinctrl would work as well, or perhaps a combination of both pinctrl
> and a regulator.


Not sure, how I can propagate "call coming from MMC/SD" to both
regulator and pinctrl.
Probably pinctrl would already know, but then it doesn't know the
voltage settings.

Let me spend some time, but atleast at this point I am not sure.

>
> What I don't like is the solution you have suggested in patch3.
>

As I said, that was easy fit into existing implementation. :)
f_sdh30 already does something similar.

Thanks,
Vaibhav
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#1224106

On Monday 14 September 2015 06:11 PM, Vaibhav Hiremath wrote:
>
>
> On Monday 14 September 2015 04:04 PM, Ulf Hansson wrote:
>> On 14 September 2015 at 11:42, Vaibhav Hiremath
>> <vaibhav.hiremath@linaro.org> wrote:
>>>
>>>
>>> On Monday 14 September 2015 03:00 PM, Ulf Hansson wrote:
>>>>
>>>> [...]
>>>>
>>>>>>>>
>>>>>>>> Could this be implemented by regulator API? From patch set 3/3, the
>>>>>>>> pxa1928
>>>>>>>> voltage_switch hook is to operate the IO pad registers, this
>>>>>>>> seems not
>>>>>>>> belong
>>>>>>>> to the SDHC IP core.
>>>>>>>>
>>>>>>>
>>>>>>> Not quite sure whether regulator would be right fit for this.
>>>>>>
>>>>>>
>>>>>>
>>>>>>    From the patche[3/3], this can be achieved by abstracting the
>>>>>> IO PAD
>>>>>> as
>>>>>> regulators
>>>>>> then, we may not need to touch the core sdhci.c. But I'm not sure
>>>>>> whether
>>>>>> this
>>>>>> is the good solution or not.
>>>>>
>>>>>
>>>>>
>>>>> Exactly...
>>>>>
>>>>>> sdhci Maintainers and experts may have better
>>>>>> suggestions.
>>>>>>
>>>>>
>>>>> Thats is the reason I stamped it as a RFC :)
>>>>>
>>>>
>>>> [...]
>>>>
>>>>   From an mmc core perspective it would be preferred if you implement
>>>> this as a regulator (vqmmc).
>>>>
>>>> Especially since we will soon have an API for how to set the I/O
>>>> voltages - and the intelligence within that API is not something we
>>>> would like to implement for each and every host driver.
>>>> https://lkml.org/lkml/2015/8/31/367
>>>>
>>>
>>>
>>> I would still consider this as a regulator specific and may not address
>>> the IO configuration within the SoC which are module specific.
>>> The API regulator_set_voltage_triplet() will not have intelligence to
>>> differentiate whether the call is coming from MMC or somewhere else.
>>>
>>> Note that, the IO pad voltage configuration which I am referring to is
>>> MMC specific and applicable only when pad is configured in MMC mode. So
>>> technically it is not simply common pad voltage configuration.
>>>
>>>
>>> And I am still not sure regulator framework would be right fit for
>>> this. Pinctrl would have been right fit, but...since I saw f_sdh30
>>> driver is already doing this, which is easy fit; so adopted the same.
>>
>> Pinctrl would work as well, or perhaps a combination of both pinctrl
>> and a regulator.
>
>
> Not sure, how I can propagate "call coming from MMC/SD" to both
> regulator and pinctrl.
> Probably pinctrl would already know, but then it doesn't know the
> voltage settings.
>
> Let me spend some time, but atleast at this point I am not sure.
>
>>

On the side note,
Lets park this patch aside, till I get back with better option.

It would be nice if you could review other patches, let them notget
blocked due to this.


Thanks,
Vaibhav
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