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

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Date:	Wed, 12 Aug 2015 15:19:20 +0200
From:	Olliver Schinagl <oliver+list@...inagl.nl>
To:	hdegoede@...hat.com, hramrach@...il.com,
	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@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [linux-sunxi] [PATCH 3/3] mmc: sunxi: use controller automatic
 clock gating.

Hey,

On 12-08-15 14:35, Hans de Goede 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 ?
It doesn't matter actually, it took some time longer, but the mmc still 
craps out even with Michal's 3 patches. I'll revert hans's earlier patch 
again and do a bit more extensive testing.
> Also given the long latencies when using manual
> clock on/off support, have you done any testing to check what
> 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 ?
>
> Regards,
>
> Hans
>
>
>
>> ---
>>   drivers/mmc/host/sunxi-mmc.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
>> index f808a02..443cab5 100644
>> --- a/drivers/mmc/host/sunxi-mmc.c
>> +++ b/drivers/mmc/host/sunxi-mmc.c
>> @@ -601,8 +601,13 @@ static int sunxi_mmc_oclk_onoff(struct 
>> sunxi_mmc_host *host, u32 oclk_en)
>>       rval = mmc_readl(host, REG_CLKCR);
>>       rval &= ~(SDXC_CARD_CLOCK_ON | SDXC_LOW_POWER_ON);
>>
>> -    if (oclk_en)
>> +    if (oclk_en) {
>>           rval |= SDXC_CARD_CLOCK_ON;
>> +        if (!host->mmc->card ||
>> +             !(host->mmc->card->quirks & MMC_QUIRK_BROKEN_CLK_GATING))
>> +
>> +            rval |= SDXC_LOW_POWER_ON;
>> +    }
>>
>>       start = jiffies;
>>       end = start + msecs_to_jiffies(750);
>>
>

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