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

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Message-ID: <CAC5umyj+gQYuLR1v73Dq78vx0NEreMDkmWe0Tk9UBuv8uc5AQw@mail.gmail.com>
Date:	Thu, 22 Oct 2015 01:11:39 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	Yaniv Gardi <ygardi@...eaurora.org>
Cc:	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?

> +       /*
>          * 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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