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

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Date:   Fri, 2 Feb 2018 08:53:09 +0530
From:   "Asutosh Das (asd)" <asutoshd@...eaurora.org>
To:     Avri Altman <Avri.Altman@....com>,
        "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

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@...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.
> 

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