Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <62d09e6f-9898-6233-dfd6-b5ba5d837571@quicinc.com>
Date:   Thu, 9 Jun 2022 07:54:13 -0600
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.6.0
Subject: Re: [PATCH] bus: mhi: Disable IRQs instead of freeing them during
 power down
Content-Language: en-US
To:     Qiang Yu <quic_qianyu@quicinc.com>, <mani@kernel.org>,
        <quic_hemantk@quicinc.com>, <loic.poulain@linaro.org>
CC:     <mhi@lists.linux.dev>, <linux-arm-msm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <1654782215-70383-1-git-send-email-quic_qianyu@quicinc.com>
From:   Jeffrey Hugo <quic_jhugo@quicinc.com>
In-Reply-To: <1654782215-70383-1-git-send-email-quic_qianyu@quicinc.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 6/9/2022 7:43 AM, Qiang Yu wrote:
> EP tends to read MSI address/data once and cache them after BME is set.
> So host should avoid changing MSI address/data after BME is set.
> 
> In pci reset function, host invokes free_irq(), which also clears MSI
> address/data in EP's PCIe config space. If the invalid address/data
> are cached and used by EP, MSI triggered by EP wouldn't be received by
> host, because an invalid MSI data is sent to an invalid MSI address.
> 
> To fix this issue, after host runs request_irq() successfully during
> mhi driver probe, let's invoke enable_irq()/disable_irq() instead of
> request_irq()/free_irq() when we want to power on and power down MHI.
> Meanwhile, Host should invoke free_irq() when mhi host driver is
> removed.

I don't think this works for hotplug, nor cases where there are multiple 
MHI devices on the system.

The EP shouldn't be caching this information for multiple reasons. 
Masking the MSIs, disabling the MSIs, changing the address when the 
affinity changes, etc.

It really feels like we are solving the problem in the wrong place.

Right now, this gets a NACK from me.

> 
> Signed-off-by: Qiang Yu <quic_qianyu@quicinc.com>
> ---
>   drivers/bus/mhi/host/init.c        | 31 +++++++++++++++++++++++++++++++
>   drivers/bus/mhi/host/pci_generic.c |  2 ++
>   drivers/bus/mhi/host/pm.c          |  4 ++--
>   3 files changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> index cbb86b2..48cb093 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -18,6 +18,7 @@
>   #include <linux/slab.h>
>   #include <linux/vmalloc.h>
>   #include <linux/wait.h>
> +#include <linux/irq.h>

Should be in alphabetical order

>   #include "internal.h"
>   
>   static DEFINE_IDA(mhi_controller_ida);
> @@ -168,6 +169,22 @@ int mhi_init_irq_setup(struct mhi_controller *mhi_cntrl)
>   	unsigned long irq_flags = IRQF_SHARED | IRQF_NO_SUSPEND;
>   	int i, ret;
>   
> +	/*
> +	 * if irq[0] has action, it represents all MSI IRQs have been
> +	 * requested, so we just need to enable them.
> +	 */

This seems like an assumption about how the interrupts are allocated and 
assigned that may not hold true for all devices.

> +	if (irq_has_action(mhi_cntrl->irq[0])) {
> +		enable_irq(mhi_cntrl->irq[0]);
> +
> +		for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
> +			if (mhi_event->offload_ev)
> +				continue;
> +
> +			enable_irq(mhi_cntrl->irq[mhi_event->irq]);
> +		}
> +		return 0;
> +	}
> +
>   	/* if controller driver has set irq_flags, use it */
>   	if (mhi_cntrl->irq_flags)
>   		irq_flags = mhi_cntrl->irq_flags;
> @@ -179,6 +196,11 @@ int mhi_init_irq_setup(struct mhi_controller *mhi_cntrl)
>   				   "bhi", mhi_cntrl);
>   	if (ret)
>   		return ret;
> +	/*
> +	 * IRQ marked IRQF_SHARED isn't recommended to use IRQ_NOAUTOEN,
> +	 * so disable it explicitly.
> +	 */
> +	disable_irq(mhi_cntrl->irq[0]);
>   
>   	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
>   		if (mhi_event->offload_ev)
> @@ -200,6 +222,8 @@ int mhi_init_irq_setup(struct mhi_controller *mhi_cntrl)
>   				mhi_cntrl->irq[mhi_event->irq], i);
>   			goto error_request;
>   		}
> +
> +		disable_irq(mhi_cntrl->irq[mhi_event->irq]);
>   	}
>   
>   	return 0;
> @@ -1003,8 +1027,14 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
>   
>   	mhi_create_debugfs(mhi_cntrl);
>   
> +	ret = mhi_init_irq_setup(mhi_cntrl);
> +	if (ret)
> +		goto error_setup_irq;
> +
>   	return 0;
>   
> +error_setup_irq:
> +	mhi_destroy_debugfs(mhi_cntrl);
>   err_release_dev:
>   	put_device(&mhi_dev->dev);
>   err_ida_free:
> @@ -1027,6 +1057,7 @@ void mhi_unregister_controller(struct mhi_controller *mhi_cntrl)
>   	struct mhi_chan *mhi_chan = mhi_cntrl->mhi_chan;
>   	unsigned int i;
>   
> +	mhi_deinit_free_irq(mhi_cntrl);
>   	mhi_destroy_debugfs(mhi_cntrl);
>   
>   	destroy_workqueue(mhi_cntrl->hiprio_wq);
> diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
> index 6fbc591..60020d0 100644
> --- a/drivers/bus/mhi/host/pci_generic.c
> +++ b/drivers/bus/mhi/host/pci_generic.c
> @@ -945,6 +945,8 @@ static void mhi_pci_remove(struct pci_dev *pdev)
>   
>   	mhi_unregister_controller(mhi_cntrl);
>   	pci_disable_pcie_error_reporting(pdev);
> +
> +	pci_free_irq_vectors(pdev);
>   }
>   
>   static void mhi_pci_shutdown(struct pci_dev *pdev)
> diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
> index dc2e8ff..190231c 100644
> --- a/drivers/bus/mhi/host/pm.c
> +++ b/drivers/bus/mhi/host/pm.c
> @@ -500,7 +500,7 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
>   	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
>   		if (mhi_event->offload_ev)
>   			continue;
> -		free_irq(mhi_cntrl->irq[mhi_event->irq], mhi_event);
> +		disable_irq(mhi_cntrl->irq[mhi_event->irq]);
>   		tasklet_kill(&mhi_event->task);
>   	}
>   
> @@ -1182,7 +1182,7 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
>   	/* Wait for shutdown to complete */
>   	flush_work(&mhi_cntrl->st_worker);
>   
> -	free_irq(mhi_cntrl->irq[0], mhi_cntrl);
> +	disable_irq(mhi_cntrl->irq[0]);
>   }
>   EXPORT_SYMBOL_GPL(mhi_power_down);
>