Re: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed

[Asutosh Das (asd)]

On 1/31/2018 1:09 PM, Avri Altman wrote:
> Hi,
> Can you elaborate how this can even happen?
> Isn't the interrupt aggregation capability should attend for those cases?
>
> Thanks,
> Avri
>
> > -----Original Message-----
> > From: linux-scsi-owner@xxxxxxxxxxxxxxx [mailto:linux-scsi-
> > owner@xxxxxxxxxxxxxxx] On Behalf Of Asutosh Das
> > Sent: Tuesday, January 30, 2018 6:54 AM
> > To: subhashj@xxxxxxxxxxxxxx; cang@xxxxxxxxxxxxxx;
> > vivek.gautam@xxxxxxxxxxxxxx; rnayak@xxxxxxxxxxxxxx;
> > vinholikatti@xxxxxxxxx; jejb@xxxxxxxxxxxxxxxxxx;
> > martin.petersen@xxxxxxxxxx
> > Cc: linux-scsi@xxxxxxxxxxxxxxx; Venkat Gopalakrishnan
> > <venkatg@xxxxxxxxxxxxxx>; Asutosh Das <asutoshd@xxxxxxxxxxxxxx>; open
> > list <linux-kernel@xxxxxxxxxxxxxxx>
> > Subject: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed
> >
> > From: Venkat Gopalakrishnan <venkatg@xxxxxxxxxxxxxx>
> >
> > As multiple requests are submitted to the ufs host controller in parallel there
> > could be instances where the command completion interrupt arrives later for a
> > request that is already processed earlier as the corresponding doorbell was
> > cleared when handling the previous interrupt. Read the interrupt status in a
> > loop after processing the received interrupt to catch such interrupts and handle
> > it.
> >
> > Signed-off-by: Venkat Gopalakrishnan <venkatg@xxxxxxxxxxxxxx>
> > Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> > ---
> >   drivers/scsi/ufs/ufshcd.c | 27 +++++++++++++++++++--------
> >   1 file changed, 19 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index
> > 8af2af3..58d81de 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -5357,19 +5357,30 @@ static irqreturn_t ufshcd_intr(int irq, void *__hba)
> >   	u32 intr_status, enabled_intr_status;
> >   	irqreturn_t retval = IRQ_NONE;
> >   	struct ufs_hba *hba = __hba;
> > +	int retries = hba->nutrs;
> >
> >   	spin_lock(hba->host->host_lock);
> >   	intr_status = ufshcd_readl(hba, REG_INTERRUPT_STATUS);
> > -	enabled_intr_status =
> > -		intr_status & ufshcd_readl(hba, REG_INTERRUPT_ENABLE);
> >
> > -	if (intr_status)
> > -		ufshcd_writel(hba, intr_status, REG_INTERRUPT_STATUS);
> > +	/*
> > +	 * There could be max of hba->nutrs reqs in flight and in worst case
> > +	 * if the reqs get finished 1 by 1 after the interrupt status is
> > +	 * read, make sure we handle them by checking the interrupt status
> > +	 * again in a loop until we process all of the reqs before returning.
> > +	 */
> > +	do {
> > +		enabled_intr_status =
> > +			intr_status & ufshcd_readl(hba,
> > REG_INTERRUPT_ENABLE);
> > +		if (intr_status)
> > +			ufshcd_writel(hba, intr_status,
> > REG_INTERRUPT_STATUS);
> > +		if (enabled_intr_status) {
> > +			ufshcd_sl_intr(hba, enabled_intr_status);
> > +			retval = IRQ_HANDLED;
> > +		}
> > +
> > +		intr_status = ufshcd_readl(hba, REG_INTERRUPT_STATUS);
> > +	} while (intr_status && --retries);
> >
> > -	if (enabled_intr_status) {
> > -		ufshcd_sl_intr(hba, enabled_intr_status);
> > -		retval = IRQ_HANDLED;
> > -	}
> >   	spin_unlock(hba->host->host_lock);
> >   	return retval;
> >   }
> > --
> > Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
> > Inc.
> > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
> > Foundation Collaborative Project.

Hi
yes - interrupt aggregation makes sense here. But there were some 
performance concerns with it; well, I don't have the data to back that 
up now though.
However, I can code it up and check it.
Will post it in some time.

-asd

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a 
Linux Foundation Collaborative Project