linux-kernel - Re: [PATCH v6 2/3] mmc: dw_mmc: Honor requests to set the clock to 0 (turn off clock)

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Date:	Mon, 26 Aug 2013 10:31:11 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Jaehoon Chung <jh80.chung@...sung.com>,
	Chris Ball <cjb@...top.org>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	James Hogan <james.hogan@...tec.com>,
	Grant Grundler <grundler@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Olof Johansson <olof@...om.net>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 2/3] mmc: dw_mmc: Honor requests to set the clock to 0
 (turn off clock)

Hi Doug,

On 08/24/2013 05:40 AM, Doug Anderson wrote:
> Jaehoon,
> 
> On Fri, Aug 23, 2013 at 6:21 AM, Jaehoon Chung <jh80.chung@...sung.com> wrote:
>> Hi Doug,
>>
>> If the clock-gating is enabled, then maybe it's continuously printed the kernel message for Bus_speed.
> 
> Can you explain?  I don't think dw_mmc has support for clock gating
> right now.  ...or are there some patches that I'm not aware of?  I
> could believe that if you've got some non-upstream clock gating
> patches that these would need to be modified to handle it...  ...but
> unless those are slated to land upstream it seems like I can't take
> them into account, can I?
If i enabled the CONFIG_MMC_CLK_GATE, the i have found the below message whenever some operation is run.
I will test more with your patch.

[    6.335000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.345000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.355000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.365000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.375000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.480000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.490000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.500000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.530000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.535000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)
[    6.545000] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)

Best Regards,
Jaehoon Chung
> 
> Thanks!
> 
> -Doug
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