linux-kernel - Re: [linux-sunxi] [PATCH 3/3] mmc: sunxi: use controller automatic clock gating.

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Date:	Wed, 12 Aug 2015 14:53:42 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Hans de Goede <hdegoede@...hat.com>
Cc:	linux-sunxi <linux-sunxi@...glegroups.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	David Lanzendörfer <david.lanzendoerfer@....ch>,
	Chen-Yu Tsai <wens@...e.org>, Arnd Bergmann <arnd@...db.de>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [linux-sunxi] [PATCH 3/3] mmc: sunxi: use controller automatic
 clock gating.

On 12 August 2015 at 14:35, Hans de Goede <hdegoede@...hat.com> wrote:
> Hi,
>
> On 12-08-15 14:23, Michal Suchanek wrote:
>>
>> When core does not set the MMC_QUIRK_BROKEN_CLK_GATING flag enable
>> automatic hardware controlled clock gating on the mmc interface.
>>
>> Signed-off-by: Michal Suchanek <hramrach@...il.com>
>
>
> In general this looks good, but I wonder how intensively this has
> been tested ?

Unlike the wrong timeout it does not cause the boards to crash frequently ;-)

It would be nice if somebody actively using some board atm tested this.

> Also given the long latencies when using manual
> clock on/off support, have you done any testing to check what

I suspect the long latency is due to the controller flushing data to
the card or something like that since it happens only under load.

> sort of latencies this adds, e.g. Both with and without
> the patch, dump all the filesystem caches:
>
> echo 3 > /proc/sys/vm/drop_caches
>
> And then do:
>
> time cat /some/small/file/on/the/sdcard
>
> Do this at least 3 time both with and without the patch, and see
> if there are any noticable differences ?

Yes, it would be good idea to test.

Thanks

Michal
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