linux-kernel - RE: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed

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Date:   Wed, 31 Jan 2018 07:39:06 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Asutosh Das <asutoshd@...eaurora.org>,
        "subhashj@...eaurora.org" <subhashj@...eaurora.org>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "vivek.gautam@...eaurora.org" <vivek.gautam@...eaurora.org>,
        "rnayak@...eaurora.org" <rnayak@...eaurora.org>,
        "vinholikatti@...il.com" <vinholikatti@...il.com>,
        "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed

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@...r.kernel.org [mailto:linux-scsi-
> owner@...r.kernel.org] On Behalf Of Asutosh Das
> Sent: Tuesday, January 30, 2018 6:54 AM
> To: subhashj@...eaurora.org; cang@...eaurora.org;
> vivek.gautam@...eaurora.org; rnayak@...eaurora.org;
> vinholikatti@...il.com; jejb@...ux.vnet.ibm.com;
> martin.petersen@...cle.com
> Cc: linux-scsi@...r.kernel.org; Venkat Gopalakrishnan
> <venkatg@...eaurora.org>; Asutosh Das <asutoshd@...eaurora.org>; open
> list <linux-kernel@...r.kernel.org>
> Subject: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed
> 
> From: Venkat Gopalakrishnan <venkatg@...eaurora.org>
> 
> 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@...eaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
> ---
>  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.