From: Adrian Hunter <adrian.hunter@intel.com>
To: Avri Altman <Avri.Altman@wdc.com>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
"James E . J . Bottomley" <jejb@linux.ibm.com>
Cc: "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Alim Akhtar <alim.akhtar@samsung.com>
Subject: Re: [PATCH 1/2] scsi: ufs: Add DeepSleep feature
Date: Mon, 5 Oct 2020 11:43:15 +0300 [thread overview]
Message-ID: <a3cd3d32-0dcf-ebaf-d6fe-e8f21539dff1@intel.com> (raw)
In-Reply-To: <BY5PR04MB67054C67CCA53AB5FC5CBCFAFC0C0@BY5PR04MB6705.namprd04.prod.outlook.com>
On 5/10/20 11:02 am, Avri Altman wrote:
> HI,
>
>> Drivers that wish to support DeepSleep need to set a new capability flag
>> UFSHCD_CAP_DEEPSLEEP and provide a hardware reset via the existing
>> ->device_reset() callback.
> I would expect that this capability controls sending SSU 4, but it only controls the sysfs entry?
The sysfs entry is the only way to request DeepSleep.
>
>>
>> It is assumed that UFS devices with wspecversion >= 0x310 support
>> DeepSleep.
>>
>> The UFS specification says to set the IMMED (immediate) flag for the
>> Start/Stop Unit command when entering DeepSleep. However some UFS
>> devices object to that, which is addressed in a subsequent patch.
> After failing to understand what the proper behavior should be with respect of the IMMED bit,
> Although I read the applicable section few time, I gave up and consult our system guy,
> Which is our jedec representative. This is his answer:
> "...
> In order to avoid uncertainty - the host need to set IMMED bit to '0' (this is explicitly specified by the standard).
> The device responds only after it switches to Pre-DeepSleep state. The host then switch to H8 and this would trigger the device to transition to DeepSleep state.
> ..."
>
> So maybe the 2nd patch isn't really needed.
Yes I managed to get it the wrong way around! I will drop patch 2 and send
V2 of patch 1 in due course.
next prev parent reply other threads:[~2020-10-05 8:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-02 12:40 [PATCH 0/2] scsi: ufs: Add DeepSleep feature Adrian Hunter
2020-10-02 12:40 ` [PATCH 1/2] " Adrian Hunter
2020-10-04 7:20 ` Avri Altman
2020-10-04 14:24 ` Avri Altman
2020-10-05 8:02 ` Avri Altman
2020-10-05 8:43 ` Adrian Hunter [this message]
2020-10-05 9:51 ` Avri Altman
2020-10-05 11:06 ` Adrian Hunter
2020-10-05 11:14 ` Avri Altman
2020-10-02 12:40 ` [PATCH 2/2] scsi: ufs: Workaround UFS devices that object to DeepSleep IMMED Adrian Hunter
2020-10-05 8:10 ` Avri Altman
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