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

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Date:   Wed, 9 Dec 2020 10:34:22 -0800
From:   Hemant Kumar <hemantk@...eaurora.org>
To:     Carl Huang <cjhuang@...eaurora.org>,
        manivannan.sadhasivam@...aro.org,
        Jeffrey Hugo <jhugo@...eaurora.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 12/7/20 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.
> 
> 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.
> 
> 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.
> +
>   	/* 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;
>   };
>   
>   /**
> 

Thanks,
Hemant

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