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Date:   Wed, 6 Jan 2021 22:51:04 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Can Guo <cang@codeaurora.org>
Cc:     linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
        kernel-team@android.com, alim.akhtar@samsung.com,
        avri.altman@wdc.com, bvanassche@acm.org,
        martin.petersen@oracle.com, stanley.chu@mediatek.com
Subject: Re: [PATCH v3 2/2] scsi: ufs: handle LINERESET with correct tm_cmd
Message-ID: <X/avWNrpOzWMj6xY@google.com>
References: <20210106214109.44041-1-jaegeuk@kernel.org>
 <20210106214109.44041-3-jaegeuk@kernel.org>
 <163fae07a94933230e0432e2ca584040@codeaurora.org>
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On 01/07, Can Guo wrote:
> On 2021-01-07 05:41, Jaegeuk Kim wrote:
> > From: Jaegeuk Kim <jaegeuk@google.com>
> > 
> > This fixes a warning caused by wrong reserve tag usage in
> > __ufshcd_issue_tm_cmd.
> > 
> > WARNING: CPU: 7 PID: 7 at block/blk-core.c:630 blk_get_request+0x68/0x70
> > WARNING: CPU: 4 PID: 157 at block/blk-mq-tag.c:82
> > blk_mq_get_tag+0x438/0x46c
> > 
> > And, in ufshcd_err_handler(), we can avoid to send tm_cmd before
> > aborting
> > outstanding commands by waiting a bit for IO completion like this.
> > 
> > __ufshcd_issue_tm_cmd: task management cmd 0x80 timed-out
> > 
> 
> Would you mind add a Fixes tag?

Ok.

> 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  drivers/scsi/ufs/ufshcd.c | 36 ++++++++++++++++++++++++++++++++----
> >  1 file changed, 32 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index 1678cec08b51..47fc8da3cbf9 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -44,6 +44,9 @@
> >  /* Query request timeout */
> >  #define QUERY_REQ_TIMEOUT 1500 /* 1.5 seconds */
> > 
> > +/* LINERESET TIME OUT */
> > +#define LINERESET_IO_TIMEOUT_MS			(30000) /* 30 sec */
> > +
> >  /* Task management command timeout */
> >  #define TM_CMD_TIMEOUT	100 /* msecs */
> > 
> > @@ -5899,6 +5902,8 @@ static void ufshcd_err_handler(struct work_struct
> > *work)
> >  	 * check if power mode restore is needed.
> >  	 */
> >  	if (hba->saved_uic_err & UFSHCD_UIC_PA_GENERIC_ERROR) {
> > +		ktime_t start = ktime_get();
> > +
> >  		hba->saved_uic_err &= ~UFSHCD_UIC_PA_GENERIC_ERROR;
> >  		if (!hba->saved_uic_err)
> >  			hba->saved_err &= ~UIC_ERROR;
> > @@ -5906,6 +5911,20 @@ static void ufshcd_err_handler(struct work_struct
> > *work)
> >  		if (ufshcd_is_pwr_mode_restore_needed(hba))
> >  			needs_restore = true;
> >  		spin_lock_irqsave(hba->host->host_lock, flags);
> > +		/* Wait for IO completion to avoid aborting IOs */
> > +		while (hba->outstanding_reqs) {
> > +			ufshcd_complete_requests(hba);
> > +			spin_unlock_irqrestore(hba->host->host_lock, flags);
> > +			schedule();
> > +			spin_lock_irqsave(hba->host->host_lock, flags);
> > +			if (ktime_to_ms(ktime_sub(ktime_get(), start)) >
> > +						LINERESET_IO_TIMEOUT_MS) {
> > +				dev_err(hba->dev, "%s: timeout, outstanding=0x%lx\n",
> > +					__func__, hba->outstanding_reqs);
> > +				break;
> > +			}
> > +		}
> > +
> >  		if (!hba->saved_err && !needs_restore)
> >  			goto skip_err_handling;
> >  	}
> > @@ -6302,9 +6321,13 @@ static irqreturn_t ufshcd_intr(int irq, void
> > *__hba)
> >  		intr_status = ufshcd_readl(hba, REG_INTERRUPT_STATUS);
> >  	}
> > 
> > -	if (enabled_intr_status && retval == IRQ_NONE) {
> > -		dev_err(hba->dev, "%s: Unhandled interrupt 0x%08x\n",
> > -					__func__, intr_status);
> > +	if (enabled_intr_status && retval == IRQ_NONE &&
> > +				!ufshcd_eh_in_progress(hba)) {
> > +		dev_err(hba->dev, "%s: Unhandled interrupt 0x%08x (0x%08x,
> > 0x%08x)\n",
> > +					__func__,
> > +					intr_status,
> > +					hba->ufs_stats.last_intr_status,
> > +					enabled_intr_status);
> >  		ufshcd_dump_regs(hba, 0, UFSHCI_REG_SPACE_SIZE, "host_regs: ");
> >  	}
> > 
> > @@ -6348,7 +6371,11 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba
> > *hba,
> >  	 * Even though we use wait_event() which sleeps indefinitely,
> >  	 * the maximum wait time is bounded by %TM_CMD_TIMEOUT.
> >  	 */
> > -	req = blk_get_request(q, REQ_OP_DRV_OUT, BLK_MQ_REQ_RESERVED);
> > +	req = blk_get_request(q, REQ_OP_DRV_OUT, BLK_MQ_REQ_RESERVED |
> > +						BLK_MQ_REQ_NOWAIT);
> 
> Sorry that I didn't pay much attention to this part of code before.
> May I know why must we use the BLK_MQ_REQ_RESERVED flag?

What I understood is the reserved tag is used when aborting outstanding
IOs when all the 32 tags were used.

> 
> Thanks,
> Can Guo.
> 
> > +	if (IS_ERR(req))
> > +		return PTR_ERR(req);
> > +
> >  	req->end_io_data = &wait;
> >  	free_slot = req->tag;
> >  	WARN_ON_ONCE(free_slot < 0 || free_slot >= hba->nutmrs);
> > @@ -9355,6 +9382,7 @@ int ufshcd_init(struct ufs_hba *hba, void
> > __iomem *mmio_base, unsigned int irq)
> > 
> >  	hba->tmf_tag_set = (struct blk_mq_tag_set) {
> >  		.nr_hw_queues	= 1,
> > +		.reserved_tags	= 1,
> 
> If we give reserved_tags as 1 and always ask for a tm requst with
> BLK_MQ_REQ_RESERVED flag set, then the tag shall only be allocated
> from the reserved sbitmap_queue, whose depth is set to 1 here.
> UFS supports tm queue depth as 8, but here is allowing only one tm
> req at a time. Why? Please correct me if my understanding is wrong.

I couldn't find tm can be issued in parallel, so thought it was issued
one at a time. If we set 8, then we can use 24 for IOs, IIUC.

Please correct me as well. I'm still trying to understand the flow.

> 
> Thanks,
> Can Guo.
> 
> >  		.queue_depth	= hba->nutmrs,
> >  		.ops		= &ufshcd_tmf_ops,
> >  		.flags		= BLK_MQ_F_NO_SCHED,