linux-kernel - Re: [PATCH 3/3] ARM: dts: exynos5422-odroidxu3: Added UHS-I bus speed support

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Message-id: <561DB290.5070903@samsung.com>
Date:	Wed, 14 Oct 2015 10:40:32 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Alim Akhtar <alim.akhtar@...il.com>
Cc:	Anand Moon <linux.amoon@...il.com>, Kukjin Kim <kgene@...nel.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Lukasz Majewski <l.majewski@...sung.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH 3/3] ARM: dts: exynos5422-odroidxu3: Added UHS-I bus speed
 support

On 10/14/2015 10:15 AM, Krzysztof Kozlowski wrote:
> On 14.10.2015 10:06, Alim Akhtar wrote:
>> +Doug
>> Hello,
>> AFAIR, dw_mmc host controller does support UHS-I [1], specially SDR50
>> and SDR104 modes.
>>
>> [1]: http://www.spinics.net/lists/linux-mmc/msg28186.html
>>
>> What I remember is, one need to set "broken-cd" property also in order
>> to make it work because of the vqmmc and vmmc connection on board. I
>> didn't find the link right now, but you can search on the web, there
>> was a long discussion about handling this.
>> Have not checked it recently, so not sure if this got broken somehow.
>>
> 
> Please, don't top post.
> 
> I am not a SD/MMC specialist (I do not feel enough confident in its
> internals) but the datasheet for 5422 does not mention UHS. However it
> mentions "High Speed DDR Mode with 200 MHz clock rate (HS400)". This
> does not look like UHS...

You're right. It's not UHS mode. it mentions eMMC's HS400 mode.
UHS and HS400 are difference mode.

eMMC mode are supported 

> https://www.sdcard.org/developers/overview/bus_speed/
> This of course is not a definite proof that 5422 does not support UHS. I
> am just saying that I couldn't find any information that *it does*.

Well, I think you want to know whether it supported or not.
Then you can find the information at User manual.
In mobile storage part of User manual, it described the overview.
Mobile storage host supports these specification:
- Secure Digital memory (SD memory version 3.0)
- Secure Digital I/O SDIO (SDIO version 3.0)
- etc...

SD3.0 is supported UHS-I mode. 
If user manual of exynos5422 is mentioned this specification, it should be supported UHS-I mode.

If my understanding is wrong, let me know, plz.

Best Regards,
Jaehoon Chung

> 
> Best regards,
> Krzysztof
> 
> 

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