linux-kernel - Re: [PATCH] mmc: core: add auto bkops support

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Date:	Tue, 21 Jun 2016 09:44:39 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Alex Lemberg <Alex.Lemberg@...disk.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	shawn.lin@...k-chips.com, Adrian Hunter <adrian.hunter@...el.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Doug Anderson <dianders@...omium.org>,
	"linux-rockchip@...ts.infradead.org" 
	<linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH] mmc: core: add auto bkops support

On 2016/6/20 21:33, Alex Lemberg wrote:
> Hi Shawn,
>
> […]
>
>>>> +
>>>> +static int mmc_stop_auto_bkops(struct mmc_card *card)
>>>> +{
>>>> +	int err = 0;
>>>> +
>>>> +	if (!card->ext_csd.auto_bkops_en)
>>>> +		return 0;
>>>> +
>>>
>>> Shouldn’t the BKOPS_STATUS be checked prior to disabling the BKOPS activity of the device?
>>>
>>
>> Hrmm.. I read the whole section of spec for it, and I did find this
>> requirement for manul bkops but not for the auto one. So what should we
>> do if using the auto one?
>>
>
> In case of AUTO BKOPS, the eMMC Device should perform internal GC
> in the same way as in case of MANUAL BKOPS.
> The only difference is a host awareness.

agree.

> Although there is no requirement in the spec, I think the driver can
> give some time to the device to perform/complete its internal GC during the idle time.
> Thus I think we can check the BKOPS_STATUS on Runtime suspend.

We shouldn't diable bkops on *runtime* suspend as it's just the right
time for firmware to do GC. We could consider to check and wait for
the status when doing poweroff, although it seems firmware should be
able to accept the disable cmd and deal the on-going work perfectly
when doing bkops without host's awareness, just the same way as suddent
power loss cases.

Also I don't know whether the firmware will reflect its status on
BKOPS_STATUS or not when enabling the auto one. I will do more test.

Anyway, thanks for sharing your thought.
Also Adrian point out that currently we trigger manual bkosp from
userspace via mmc-utils, and I agreed we shouldn't force kernel stack
to enable it defaultly. So I'm prone not to update this $SUBJECT and
migrate it to mmc-utils later.

>
> […]
>
> Thanks,
> Alex
>

-- 
Best Regards
Shawn Lin