linux-kernel - Re: [PATCH] mhi: use irq_flags if client driver configures it

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Message-ID: <bf5409bb-adaf-d2ad-8606-cd8a3df8bc5b@codeaurora.org>
Date:   Wed, 9 Dec 2020 12:48:05 -0700
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Hemant Kumar <hemantk@...eaurora.org>,
        Carl Huang <cjhuang@...eaurora.org>,
        manivannan.sadhasivam@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mhi: use irq_flags if client driver configures it

On 12/9/2020 11:34 AM, Hemant Kumar wrote:
> 
> 
> On 12/7/20 7:55 PM, Carl Huang wrote:
>> If client driver has specified the irq_flags, mhi uses this specified
>> irq_flags. Otherwise, mhi uses default irq_flags.
>>
>> The purpose of this change is to support one MSI vector for QCA6390.
>> MHI will use one same MSI vector too in this scenario.
>>
>> In case of one MSI vector, IRQ_NO_BALANCING is needed when irq handler
>> is requested. The reason is if irq migration happens, the msi_data may
>> change too. However, the msi_data is already programmed to QCA6390
>> hardware during initialization phase. This msi_data inconsistence will
>> result in crash in kernel.

I'm confused as to how this happens.

>>
>> Another issue is in case of one MSI vector, IRQF_NO_SUSPEND will trigger
>> WARNINGS because QCA6390 wants to disable the IRQ during the suspend.
>>
>> To avoid above two issues, QCA6390 driver specifies the irq_flags in case
>> of one MSI vector when mhi_register_controller is called.

Surely this change should be in a series where there is a following 
change which updates the QCA6390 driver?

>>
>> Signed-off-by: Carl Huang <cjhuang@...eaurora.org>
>> ---
>>   drivers/bus/mhi/core/init.c | 9 +++++++--
>>   include/linux/mhi.h         | 1 +
>>   2 files changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
>> index 0ffdebd..5f74e1e 100644
>> --- a/drivers/bus/mhi/core/init.c
>> +++ b/drivers/bus/mhi/core/init.c
>> @@ -148,12 +148,17 @@ int mhi_init_irq_setup(struct mhi_controller 
>> *mhi_cntrl)
>>   {
>>       struct mhi_event *mhi_event = mhi_cntrl->mhi_event;
>>       struct device *dev = &mhi_cntrl->mhi_dev->dev;
>> +    unsigned long irq_flags = IRQF_SHARED | IRQF_NO_SUSPEND;
>>       int i, ret;
>> +    /* if client driver has set irq_flags, use it */
>> +    if (mhi_cntrl->irq_flags)
>> +        irq_flags = mhi_cntrl->irq_flags;
> Jeff if i remember correctly your use case also have one dedicated irq 
> line for all the MSIs, just want to confirm if you are fine with this 
> change ? i was wondering if any input check is required for irq_flags 
> passed by controller, or responsibility is on controller for any 
> undesired behavior. Like passing IRQF_SHARED and IRQF_ONESHOT when one 
> irq line is shared among multiple MSIs.

This feels a bit weird to me, but I don't think it'll cause a problem.

If we are allowing the controller to specify flags, should they be in a 
per irq manner?

>> +
>>       /* Setup BHI_INTVEC IRQ */
>>       ret = request_threaded_irq(mhi_cntrl->irq[0], mhi_intvec_handler,
>>                      mhi_intvec_threaded_handler,
>> -                   IRQF_SHARED | IRQF_NO_SUSPEND,
>> +                   irq_flags,
>>                      "bhi", mhi_cntrl);
>>       if (ret)
>>           return ret;
>> @@ -171,7 +176,7 @@ int mhi_init_irq_setup(struct mhi_controller 
>> *mhi_cntrl)
>>           ret = request_irq(mhi_cntrl->irq[mhi_event->irq],
>>                     mhi_irq_handler,
>> -                  IRQF_SHARED | IRQF_NO_SUSPEND,
>> +                  irq_flags,
>>                     "mhi", mhi_event);
>>           if (ret) {
>>               dev_err(dev, "Error requesting irq:%d for ev:%d\n",
>> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
>> index d4841e5..f039e58 100644
>> --- a/include/linux/mhi.h
>> +++ b/include/linux/mhi.h
>> @@ -442,6 +442,7 @@ struct mhi_controller {
>>       bool fbc_download;
>>       bool pre_init;
>>       bool wake_set;
>> +    unsigned long irq_flags;

You don't document this.  That gets a NACK from me.

>>   };
>>   /**
>>
> 
> Thanks,
> Hemant
> 


-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.