Re: [PATCH v2 6/6] mhi: pci_generic: Add support for runtime PM

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Mar 05, 2021 at 01:47:58PM +0100, Loic Poulain wrote:
> When the device is idle it is possible to move it into the lowest MHI
> PM state (M3). In that mode, all MHI operations are suspended and the
> PCI device can be safely put into PCI D3 state.
> 
> The device is then resumed from D3/M3 either because of host initiated
> MHI operation (e.g. buffer TX) or because the device (modem) has
> triggered wake-up via PME feature (e.g. on incoming data).
> 
> Same procedures can be used for system wide or runtime suspend/resume.
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> ---
>  v2: replace force_runtime_suspend/resume via local function to ensure
>      device is always resumed during system resume whatever its runtime
>      pm state.
> 
>  drivers/bus/mhi/pci_generic.c | 95 +++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 86 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/bus/mhi/pci_generic.c b/drivers/bus/mhi/pci_generic.c
> index 4ab0aa8..e36f5a9 100644
> --- a/drivers/bus/mhi/pci_generic.c
> +++ b/drivers/bus/mhi/pci_generic.c
> @@ -14,6 +14,7 @@
>  #include <linux/mhi.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/timer.h>
>  #include <linux/workqueue.h>
>  
> @@ -274,6 +275,7 @@ MODULE_DEVICE_TABLE(pci, mhi_pci_id_table);
>  
>  enum mhi_pci_device_status {
>  	MHI_PCI_DEV_STARTED,
> +	MHI_PCI_DEV_SUSPENDED,
>  };
>  
>  struct mhi_pci_device {
> @@ -306,6 +308,11 @@ static void mhi_pci_status_cb(struct mhi_controller *mhi_cntrl,
>  	case MHI_CB_FATAL_ERROR:
>  	case MHI_CB_SYS_ERROR:
>  		dev_warn(&pdev->dev, "firmware crashed (%u)\n", cb);
> +		pm_runtime_forbid(&pdev->dev);
> +		break;
> +	case MHI_CB_EE_MISSION_MODE:
> +		pm_runtime_mark_last_busy(&pdev->dev);

Do you really need to update the last_busy time here? You're already updating it
before each runtime_put() call and those will overwrite this value.

> +		pm_runtime_allow(&pdev->dev);
>  		break;
>  	default:
>  		break;
> @@ -427,13 +434,19 @@ static int mhi_pci_get_irqs(struct mhi_controller *mhi_cntrl,

[...]

> -static int  __maybe_unused mhi_pci_suspend(struct device *dev)
> +static int  __maybe_unused mhi_pci_runtime_suspend(struct device *dev)
>  {
>  	struct pci_dev *pdev = to_pci_dev(dev);
>  	struct mhi_pci_device *mhi_pdev = dev_get_drvdata(dev);
>  	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
> +	int err;
> +
> +	if (test_and_set_bit(MHI_PCI_DEV_SUSPENDED, &mhi_pdev->status))
> +		return 0;
>  
>  	del_timer(&mhi_pdev->health_check_timer);
>  	cancel_work_sync(&mhi_pdev->recovery_work);
>  
> +	if (!test_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status) ||
> +			mhi_cntrl->ee != MHI_EE_AMSS)
> +		goto pci_suspend; /* Nothing to do at MHI level */
> +
>  	/* Transition to M3 state */
> -	mhi_pm_suspend(mhi_cntrl);
> +	err = mhi_pm_suspend(mhi_cntrl);
> +	if (err) {
> +		dev_err(&pdev->dev, "failed to suspend device: %d;\n", err);

Remove the semicolon after "%d"

> +		clear_bit(MHI_PCI_DEV_SUSPENDED, &mhi_pdev->status);
> +		return -EBUSY;
> +	}
>  
> +pci_suspend:
>  	pci_disable_device(pdev);
>  	pci_wake_from_d3(pdev, true);
>  
>  	return 0;
>  }
>  
> -static int __maybe_unused mhi_pci_resume(struct device *dev)
> +static int __maybe_unused mhi_pci_runtime_resume(struct device *dev)
>  {
>  	struct pci_dev *pdev = to_pci_dev(dev);
>  	struct mhi_pci_device *mhi_pdev = dev_get_drvdata(dev);
>  	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
>  	int err;
>  
> +	if (!test_and_clear_bit(MHI_PCI_DEV_SUSPENDED, &mhi_pdev->status))
> +		return 0;
> +
>  	err = pci_enable_device(pdev);
>  	if (err)
>  		goto err_recovery;
> @@ -740,6 +786,13 @@ static int __maybe_unused mhi_pci_resume(struct device *dev)
>  	pci_set_master(pdev);
>  	pci_wake_from_d3(pdev, false);
>  
> +	/* It can be a remote wakeup (no mhi runtime_get), update access time */
> +	pm_runtime_mark_last_busy(dev);

I think this should be moved after mhi_pm_resume().

Thanks,
Mani