From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Asutosh Das (asd)" Subject: Re: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed Date: Mon, 5 Feb 2018 10:27:02 +0530 Message-ID: References: <1517288066-13171-1-git-send-email-asutoshd@codeaurora.org> <6ca20a27-3c10-bf0e-35e7-542b7ab77356@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <6ca20a27-3c10-bf0e-35e7-542b7ab77356@codeaurora.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Avri Altman , "subhashj@codeaurora.org" , "cang@codeaurora.org" , "vivek.gautam@codeaurora.org" , "rnayak@codeaurora.org" , "vinholikatti@gmail.com" , "jejb@linux.vnet.ibm.com" , "martin.petersen@oracle.com" Cc: "linux-scsi@vger.kernel.org" , Venkat Gopalakrishnan , open list List-Id: linux-scsi@vger.kernel.org On 2/2/2018 8:53 AM, Asutosh Das (asd) wrote: > 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@vger.kernel.org [mailto:linux-scsi- >>> owner@vger.kernel.org] On Behalf Of Asutosh Das >>> Sent: Tuesday, January 30, 2018 6:54 AM >>> To: subhashj@codeaurora.org; cang@codeaurora.org; >>> vivek.gautam@codeaurora.org; rnayak@codeaurora.org; >>> vinholikatti@gmail.com; jejb@linux.vnet.ibm.com; >>> martin.petersen@oracle.com >>> Cc: linux-scsi@vger.kernel.org; Venkat Gopalakrishnan >>> ; Asutosh Das ; open >>> list >>> Subject: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed >>> >>> From: Venkat Gopalakrishnan >>> >>> 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 >>> Signed-off-by: Asutosh Das >>> --- >>>   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 > Hi Avri, I went through the UFS HCI - v2.1 spec. Specifically, in sec 7.2.3 it explicitly mentions that the software should determine if new TRs were completed since the interrupt status was last read/cleared. This step is independent of aggregation. So I think the above implementation makes sense. Please let me know if I understood your concern correctly. -asd -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project