linux-kernel - Re: Warnings for invalid VDD (sdhci-s3c)

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Date:	Thu, 24 Mar 2016 17:42:55 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Jisheng Zhang <jszhang@...vell.com>,
	Jaehoon Chung <jh80.chung@...sung.com>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	ludovic.desroches@...el.com,
	"Ivan T. Ivanov" <ivan.ivanov@...aro.org>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org
Subject: Re: Warnings for invalid VDD (sdhci-s3c)

On 24.03.2016 17:24, Jisheng Zhang wrote:
> Hi,
> 
> On Thu, 24 Mar 2016 17:09:27 +0900 Jaehoon Chung wrote:
> 
>> Hi,
>>
>> On 03/24/2016 04:58 PM, Jisheng Zhang wrote:
>>> Hi,
>>>
>>> On Thu, 24 Mar 2016 16:28:56 +0900 Krzysztof Kozlowski wrote:
>>>   
>>>> Hi,
>>>>
>>>> After 918f4cbd4340 ("mmc: sdhci: restore behavior when setting VDD via
>>>> external regulator") On Trats2 board I see warnings for invalid VDD
>>>> value (2.8V):
>>>>
>>>> [    3.119656] ------------[ cut here ]------------
>>>> [    3.119666] WARNING: CPU: 3 PID: 90 at
>>>> ../drivers/mmc/host/sdhci.c:1234 sdhci_do_set_ios+0x4cc/0x5e0
>>>> [    3.119669] mmc0: Invalid vdd 0x10  
>>>
>>> Per my understanding, the wrong vdd indicates a wrong ocr, what's the voltage of
>>> this host's vmmc regulator?  
>>
>> As i know, it's fixed-voltage with gpio on trats2. It's 2.8V.
>> I didn't check this entirely..need to check ocr value.
>>
> 
> I may know the reason. the vmmc is 2.8v, then mmc_regulator_get_supply() convert
> the value to a ocr as 0x10. The key here is that the 2.8v is invalid in SDHCI
> case and isn't accepted by current sdhci driver.

Yeah, I already wrote that. It is the part of the warning and my email.
Our regulator is fixed at 2.8 which is 0x10. :)

> I dunno the elegant solution to handle this case, let's wait for sdhci maintainers
> idea.

Hmm...

Best regards,
Krzysztof