Re: [PATCH] arm64: dts: rockchip: Fix rk3328-roc-cc sdmmcio-regulator

From: Robin Murphy <robin.murphy@arm.com>
To: Adam Van Ymeren <adam@vany.ca>,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Cc: Heiko Stuebner <heiko@sntech.de>
Subject: Re: [PATCH] arm64: dts: rockchip: Fix rk3328-roc-cc sdmmcio-regulator
Date: Sat, 1 Feb 2020 17:46:24 +0000	[thread overview]
Message-ID: <d8a8b696-268b-1ea8-7b5e-406a651011ff@arm.com> (raw)
In-Reply-To: <4a6a9d81-c831-4167-7fbf-64805940fb6f@vany.ca>

On 2020-02-01 3:41 pm, Adam Van Ymeren wrote:
> 
> On 2020-02-01 5:51 a.m., Robin Murphy wrote:
>> Hi Adam,
>>
>> On 2020-01-31 11:38 pm, Adam Van Ymeren wrote:
>>> With this change the kernel successfully finds the SD Card and can load
>>> a rootfs from it.  Tested on hardware.
>>>
>>> Signed-off-by: Adam Van Ymeren <adam@vany.ca>
>>>
>>> diff -uprN -X linux-5.5/Documentation/dontdiff
>>> linux-5.5-orig/arch/arm64/boot/dts/rockchip/rk3328-roc-cc.dts
>>> linux-5.5/arch/arm64/boot/dts/rockchip/rk3328-roc-cc.dts
>>> --- linux-5.5-orig/arch/arm64/boot/dts/rockchip/rk3328-roc-cc.dts
>>> 2020-01-26 19:23:03.000000000 -0500
>>> +++ linux-5.5/arch/arm64/boot/dts/rockchip/rk3328-roc-cc.dts
>>> 2020-01-31 16:26:35.377075419 -0500
>>> @@ -44,7 +44,7 @@
>>>          vcc_sdio: sdmmcio-regulator {
>>>            compatible = "regulator-gpio";
>>> -        gpios = <&grf_gpio 0 GPIO_ACTIVE_HIGH>;
>>> +        gpios = <&gpio0 RK_PD1 GPIO_ACTIVE_HIGH>;
>>
>> Given that the RK3328 datasheet has no mention of GPIO0_D1 existing at
>> all, how sure are you that this is correct - have you tested cards in
>> both 3.3V and 1.8V (UHS-1) signalling modes?
>>
>> The ROC-RK3328-CC schematics show GPIO_MUTE being used to bias the
>> feedback pin of an adjustable regulator supplying the SDMMC0 I/O
>> domain, so it seems more likely that the pin is correct but the states
>> (or the polarity) are backwards.
> 
> 
> Hmm yeah after reading the schematics this doesn't make sense.  I took
> it from the vendors source tree[1], and it definitely allowed my system
> to boot when it wouldn't before, but I only tried a 3.3V card.  I'll try
> just changing the polarity.  I'll also find a UHS-1 card and test that,
> any advice on how to verify that it's running in the 1.8V mode?

My preferred method is to stick a meter on either the uSD socket pins or 
the regulator itself and wiggle the GPIO from userspace, but preferably 
only if the board can run without a card inserted.

That said, I just suddenly remembered about regulator GPIOs being quirky 
for legacy ABI reasons - I'm now 99% sure that you should simply need to 
add the "enable-active-high" property to make it actually work as expected.

Robin.

>
> [1]
> https://github.com/FireflyTeam/kernel/blob/rk3328/firefly/arch/arm64/boot/dts/rockchip/rk3328-firefly-core.dtsi#L89
> 
> 
> Thanks for the review!
> 
> -Adam
> 

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