linux-kernel - Re: [PATCH v2 0/6] Add support of inverting power control and some minor cleanup

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Date:	Fri, 12 Aug 2016 10:57:58 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Jaehoon Chung <jh80.chung@...sung.com>,
	Shawn Lin <shawn.lin@...k-chips.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	shawn.lin@...k-chips.com, Rob Herring <robh+dt@...nel.org>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Heiko Stuebner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/6] Add support of inverting power control and some
 minor cleanup

On 2016/8/11 18:08, Jaehoon Chung wrote:
> Hi Shawn,
>
> On 08/09/2016 10:49 AM, Shawn Lin wrote:
>> Hi,
>>
>> On 2016/8/8 18:24, Jaehoon Chung wrote:
>>> Hi Shawn,
>>>
>>> On 08/07/2016 10:33 AM, Shawn Lin wrote:
>>>> By default, dw_mmc outputs high level voltage to indicate powering
>>>> up the card and outputs low level vcltage to indicate powering
>>>> off the card. But that is not always correct. The power io should
>>>> be able to control different kind of hw components to supply or
>>>> cutoff power to the card. We have boards that need this patchset
>>>> to make the power control correct. Meanwhile let's expose it to
>>>> DT for board-specific usage.
>>>
>>> I have a question for this patch-set. Does DWMMC IP support to invert ON/OFF at Power Enable register?
>>
>> No.
>>
>>> Hmm..Well, if use the DW_MMC_CARD_PWR_INVERT, it should also be the similar behavior with Quirks.
>>
>> yup, it makes the power control more complicated than before. :(
>>
>>>
>>> Other flags are related with dwmmc IP. But this flag (DW_MMC_CARD_PWR_INVERT) is not related with IP side.
>>> I understood why you needs to add this flag..Is rockchip designed to invert the power controlling?
>>
>> We don't invert the power controlling but our customers do.
>> The HW componet looks like some discrete LDOs which enable the related
>> power supply when outputing low voltage from pwren..
>
> Is it related with PWREN register?
> I'm checking the TRM for PWREN register..
>
> "Optional feature; ports can be used as general-purpose outputs."
>
> Does it use the ports as GPIO?
>
>>
>>>
>>> But it's not general case. We can discuss about this.
>>
>> I have a solution which is to add gpio power control for slot-gpio of
>> mmc core. once finished, we could add pwr_cap_invert just like what we
>> did for cd/wp invert control..
>
> I'm not sure that it's right that add the gpio power control into mmc core.
> slot-gpio? i think it can use the regulator framework with gpio.

yup, I'm looking this and seems it's fine to register a regulator-gpio
and stuff it for vmmc-supply of sdmmc. I will test it, really helpful.

thanks!

> I don't have a lot knowledge of power, but it might be controlled whether active is low or high.
> So i think it doesn't need to add for entire mmc controller.
>
> Best Regards,
> Jaehoon Chung
>
>>
>> Then we could remove PWREN from the default state of
>> pinctrl inside the sdmmc dt node, and let dwmmc request gpio power
>> control stuff after paring the property for pwr_cap_invert..
>>
>> More over, it well fit for all mmc host's requirement of gpio
>> power control and inverted control if they want it. :)
>>
>>
>> That should be legit for us?
>> If it sounds ok to you and Ulf, I will come up with a RFC one for
>> community to comment it.:)
>>
>>>
>>> Best Regards,
>>> Jaehoon Chung
>>>
>>>>
>>>>
>>>> Changes in v2:
>>>> - fix copy-paste err and typo
>>>>
>>>> Shawn Lin (6):
>>>>   dt-bindings: rockchip-dw-mshc: add description of
>>>>     rockchip,power-invert
>>>>   mmc: dw_mmc: cleanup power setting of set_ios callback
>>>>   mmc: dw_mmc: split out dw_mci_set_power
>>>>   mmc: dw_mmc: split out dw_mci_set_power_reg
>>>>   mmc: dw_mmc: support inverted power control
>>>>   mmc: dw_mmc-rockchip: add parsing of power control from DT
>>>>
>>>>  .../devicetree/bindings/mmc/rockchip-dw-mshc.txt   |   6 +
>>>>  drivers/mmc/host/dw_mmc-rockchip.c                 |   8 ++
>>>>  drivers/mmc/host/dw_mmc.c                          | 134 ++++++++++++---------
>>>>  drivers/mmc/host/dw_mmc.h                          |   1 +
>>>>  4 files changed, 90 insertions(+), 59 deletions(-)
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
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-- 
Best Regards
Shawn Lin