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

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Date:	Thu, 23 Jun 2016 09:33:24 +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

在 2016/6/22 22:08, Alex Lemberg 写道:
> HI Shawn,
>
> On 6/21/16, 4:44 AM, "Shawn Lin" <shawn.lin@...k-chips.com> wrote:
>
>> 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.
>
> If I am not wrong, in current implementation of runtime suspend,
> the driver stops BKOPS (send HPI) just before sending sleep command,
> see _mmc_suspend(), depends on “MMC_CAP_AGGRESSIVE_PM” flag.
> In this case, the eMMC device will not have enough time to perform internal
> BKOPS in both – Manual and Auto BKOPS configurations.
>

ye, so it seems a pre-exiting issue before introducing auto bkops?
I think we can push another patch to improve it but not handling
it for this $SUBJECT, does it sound ok to you?

> For the poweroff, it should be OK with a current implementation of
> PON (mmc_poweroff_notify())
>
>>
>> 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
>>
>


-- 
Best Regards
Shawn Lin