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SubjectRe: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed
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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
>> <venkatg@codeaurora.org>; Asutosh Das <asutoshd@codeaurora.org>; open
>> list <linux-kernel@vger.kernel.org>
>> Subject: [PATCH 1/1] scsi: ufs: make sure all interrupts are processed
>>
>> From: Venkat Gopalakrishnan <venkatg@codeaurora.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@codeaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.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

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