linux-kernel - Re: [PATCH v1 16/17] scsi: ufs: add delay before putting UFS rails in low power modes

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Date:	Mon, 26 Oct 2015 15:08:01 -0000
From:	ygardi@...eaurora.org
To:	"Akinobu Mita" <akinobu.mita@...il.com>
Cc:	"Yaniv Gardi" <ygardi@...eaurora.org>,
	"Jej B" <james.bottomley@...senpartnership.com>,
	"Paul Bolle" <pebolle@...cali.nl>,
	"Christoph Hellwig" <hch@...radead.org>,
	"LKML" <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	linux-arm-msm@...r.kernel.org, "Santosh Y" <santoshsy@...il.com>,
	linux-scsi-owner@...r.kernel.org,
	"Subhash Jadavani" <subhashj@...eaurora.org>,
	"Gilad Broner" <gbroner@...eaurora.org>,
	"Dolev Raviv" <draviv@...eaurora.org>,
	"Vinayak Holikatti" <vinholikatti@...il.com>,
	"James E.J. Bottomley" <jbottomley@...n.com>
Subject: Re: [PATCH v1 16/17] scsi: ufs: add delay before putting UFS rails
 in low power modes

> 2015-09-13 23:52 GMT+09:00 Yaniv Gardi <ygardi@...eaurora.org>:
>> We put the UFS device in sleep state & UFS link in hibern8 state during
>> runtime suspaned. After this we put all the UFS rails in low power
>> modes immediately but it seems some devices may still draw more than
>> sleep current from UFS rails (especially from VCCQ rail) atleast for
>> 500us.
>> To avoid this situation, this change adds 2ms delay before putting
>> these UFS rails in LPM mode.
>>
>> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
>> Signed-off-by: Yaniv Gardi <ygardi@...eaurora.org>
>>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 20b4c0e..786df28 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -5694,6 +5694,15 @@ out:
>>  static void ufshcd_vreg_set_lpm(struct ufs_hba *hba)
>>  {
>>         /*
>> +        * It seems some UFS devices may keep drawing more than sleep
>> current
>> +        * (atleast for 500us) from UFS rails (especially from VCCQ
>> rail).
>> +        * To avoid this situation, add 2ms delay before putting these
>> UFS
>> +        * rails in LPM mode.
>> +        */
>> +       if (!ufshcd_is_link_active(hba))
>> +               usleep_range(2000, 2100);
>> +
>
> Shouldn't we define dev_quirks for this?

as you suggested, in v2 i added a device quirk for that.

>
>> +       /*
>>          * If UFS device is either in UFS_Sleep turn off VCC rail to
>> save some
>>          * power.
>>          *
>> --
>> 1.8.5.2
>>
>> --
>> QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc. is a
>> member of Code Aurora Forum, hosted by The Linux Foundation
>> --
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>


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