linux-kernel - Re: [PATCH v2 3/5] bus: mhi: host: pci_generic: Remove MHI driver and ensure graceful device recovery

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Message-ID: <68f18f09-913d-4ef9-bd13-ad32c1d5f8ca@oss.qualcomm.com>
Date: Thu, 10 Jul 2025 14:42:38 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Vivek.Pernamitta@...cinc.com, Manivannan Sadhasivam <mani@...nel.org>
Cc: mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vivek Pernamitta <quic_vpernami@...cinc.com>
Subject: Re: [PATCH v2 3/5] bus: mhi: host: pci_generic: Remove MHI driver and
 ensure graceful device recovery

On 7/10/25 10:58 AM, Vivek.Pernamitta@...cinc.com wrote:
> From: Vivek Pernamitta <quic_vpernami@...cinc.com>
> 
> When the MHI driver is removed from the host side, it is crucial to ensure
> graceful recovery of the device. To achieve this, the host driver will
> perform the following steps:
> 
> 1. Disable SRIOV for any SRIOV-enabled devices on the Physical Function.
> 2. Perform a SOC_RESET on Physical Function (PF).
> 
> Disabling SRIOV ensures that all virtual functions are properly shut down,
> preventing any potential issues during the reset process. Performing
> SOC_RESET on each physical function guarantees that the device is fully
> reset and ready for subsequent operations.
> 
> Signed-off-by: Vivek Pernamitta <quic_vpernami@...cinc.com>
> ---
>  drivers/bus/mhi/host/pci_generic.c | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
> index 4bafe93b56c54e2b091786e7fcd68a36c8247b8e..2d1381006293412fbc593316e5c7f0f59ac74da8 100644
> --- a/drivers/bus/mhi/host/pci_generic.c
> +++ b/drivers/bus/mhi/host/pci_generic.c
> @@ -45,6 +45,8 @@
>   * @sideband_wake: Devices using dedicated sideband GPIO for wakeup instead
>   *		   of inband wake support (such as sdx24)
>   * @no_m3: M3 not supported
> + * @reset_on_driver_unbind: Set true for devices support SOC reset and
> + *				 perform it when unbinding driver
>   */
>  struct mhi_pci_dev_info {
>  	const struct mhi_controller_config *config;
> @@ -58,6 +60,7 @@ struct mhi_pci_dev_info {
>  	unsigned int mru_default;
>  	bool sideband_wake;
>  	bool no_m3;
> +	bool reset_on_driver_unbind;
>  };
>  
>  #define MHI_CHANNEL_CONFIG_UL(ch_num, ch_name, el_count, ev_ring) \
> @@ -300,6 +303,7 @@ static const struct mhi_pci_dev_info mhi_qcom_qdu100_info = {
>  	.dma_data_width = 32,
>  	.sideband_wake = false,
>  	.no_m3 = true,
> +	.reset_on_driver_unbind = true,

It seems rather unlikely that out off all MHI devices, only QDU100
needs this quirk when working under SR-IOV

>  };
>  
>  static const struct mhi_channel_config mhi_qcom_sa8775p_channels[] = {
> @@ -970,6 +974,7 @@ struct mhi_pci_device {
>  	struct work_struct recovery_work;
>  	struct timer_list health_check_timer;
>  	unsigned long status;
> +	bool reset_on_driver_unbind;
>  };
>  
>  static int mhi_pci_read_reg(struct mhi_controller *mhi_cntrl,
> @@ -1270,6 +1275,11 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	mhi_cntrl->mru = info->mru_default;
>  	mhi_cntrl->name = info->name;
>  
> +	/* Assign reset functionalities only for PF */
> +	if (pdev->is_physfn)
> +		mhi_pdev->reset_on_driver_unbind = info->reset_on_driver_unbind;
> +
> +

Double \n

>  	if (info->edl_trigger)
>  		mhi_cntrl->edl_trigger = mhi_pci_generic_edl_trigger;
>  
> @@ -1336,7 +1346,7 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	return err;
>  }
>  
> -static void mhi_pci_remove(struct pci_dev *pdev)
> +static void mhi_pci_resource_deinit(struct pci_dev *pdev)
>  {
>  	struct mhi_pci_device *mhi_pdev = pci_get_drvdata(pdev);
>  	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
> @@ -1352,6 +1362,20 @@ static void mhi_pci_remove(struct pci_dev *pdev)
>  	/* balancing probe put_noidle */
>  	if (pci_pme_capable(pdev, PCI_D3hot))
>  		pm_runtime_get_noresume(&pdev->dev);
> +}
> +
> +static void mhi_pci_remove(struct pci_dev *pdev)
> +{
> +	struct mhi_pci_device *mhi_pdev = pci_get_drvdata(pdev);
> +	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
> +
> +	/* Disable SRIOV */
> +	pci_disable_sriov(pdev);
> +	mhi_pci_resource_deinit(pdev);
> +	if (mhi_pdev->reset_on_driver_unbind) {

Can we not simply check for pdev->is_physfn?

> +		dev_info(&pdev->dev, "perform SOC reset\n");

Is the logspam really necessary?

> +		mhi_soc_reset(mhi_cntrl);
> +	}

Konrad