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From: Stanley Chu <stanley.chu@mediatek.com>
To: "Bean Huo (beanhuo)" <beanhuo@micron.com>
Cc: "bvanassche@acm.org" <bvanassche@acm.org>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"andy.teng@mediatek.com" <andy.teng@mediatek.com>,
	"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
	"chun-hung.wu@mediatek.com" <chun-hung.wu@mediatek.com>,
	"kuohong.wang@mediatek.com" <kuohong.wang@mediatek.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"avri.altman@wdc.com" <avri.altman@wdc.com>,
	"martin.peter~sen@oracle.com" <martin.peter~sen@oracle.com>,
	"cang@codeaurora.org" <cang@codeaurora.org>,
	"peter.wang@mediatek.com" <peter.wang@mediatek.com>,
	"alim.akhtar@samsung.com" <alim.akhtar@samsung.com>,
	"matthias.bgg@gmail.com" <matthias.bgg@gmail.com>,
	"linux-mediatek@lists.infradead.org"
	<linux-mediatek@lists.infradead.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"asutoshd@codeaurora.org" <asutoshd@codeaurora.org>
Subject: RE: [EXT] [PATCH v7 3/7] scsi: ufs: introduce common and flexible delay function
Date: Thu, 19 Mar 2020 08:10:35 +0800
Message-ID: <1584576635.14250.63.camel@mtksdccf07> (raw)
In-Reply-To: <BN7PR08MB5684DA8C4FB4304CDAE39440DBF70@BN7PR08MB5684.namprd08.prod.outlook.com>

Hi Bean,

On Wed, 2020-03-18 at 22:10 +0000, Bean Huo (beanhuo) wrote:
> Hi, Stanley
> > 
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index
> > 314e808b0d4e..a42a84164dec 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -597,6 +597,18 @@ static void ufshcd_print_pwr_info(struct ufs_hba *hba)
> >  		 hba->pwr_info.hs_rate);
> >  }
> > 
> > +void ufshcd_delay_us(unsigned long us, unsigned long tolerance) {
> > +	if (!us)
> > +		return;
> > +
> > +	if (us < 10)
> > +		udelay(us);
> > +	else
> > +		usleep_range(us, us + tolerance);
> > +}
> > +EXPORT_SYMBOL_GPL(ufshcd_delay_us);
> > +
> In this way, the callers of ufshcd_delay_us(), can directly call udelay() or usleep_range(), what is exist meaning of ufshcd_delay_us()?

Sure, the callers always can directly call udelay() or usleep_range().

The customizable delay (either by hosts or devices) value in UFS driver
is becoming more and more, like "reference clock gating delay" and
introduced "hce_enable_delay". The customized delay time could be 0, <
10 us, or >= 10 us in real cases. Hence this function can help driver
simplify the driver and user's decision of "just passed without any
delay" or "choosing a suitable delay function according to the delay
time".

Thanks,
Stanley Chu

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Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-18 10:40 [PATCH v7 0/7] scsi: ufs: some cleanups and make the delay for host enabling customizable Stanley Chu
2020-03-18 10:40 ` [PATCH v7 1/7] scsi: ufs: fix uninitialized tx_lanes in ufshcd_disable_tx_lcc() Stanley Chu
2020-03-18 10:40 ` [PATCH v7 2/7] scsi: ufs: use an enum for host capabilities Stanley Chu
2020-03-18 22:42   ` [EXT] " Bean Huo (beanhuo)
2020-03-18 10:40 ` [PATCH v7 3/7] scsi: ufs: introduce common and flexible delay function Stanley Chu
2020-03-18 22:10   ` [EXT] " Bean Huo (beanhuo)
2020-03-19  0:10     ` Stanley Chu [this message]
2020-03-18 10:40 ` [PATCH v7 4/7] scsi: ufs-mediatek: use common delay function for required places Stanley Chu
2020-03-18 10:40 ` [PATCH v7 5/7] scsi: ufs: allow customized delay for host enabling Stanley Chu
2020-03-18 10:40 ` [PATCH v7 6/7] scsi: ufs: make HCE polling more compact to improve initialization latency Stanley Chu
2020-03-18 10:40 ` [PATCH v7 7/7] scsi: ufs-mediatek: customize the delay for host enabling Stanley Chu
2020-03-27  2:09 ` [PATCH v7 0/7] scsi: ufs: some cleanups and make the delay for host enabling customizable Martin K. Petersen

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