Re: [Linux-kernel-mentees] [PATCH v2 01/15] scsi: megaraid_sas: use generic power management

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Jul 20, 2020 at 07:04:14PM +0530, Vaibhav Gupta wrote:
> With legacy PM hooks, it was the responsibility of a driver to manage PCI
> states and also the device's power state. The generic approach is to let
> the PCI core handle the work.
> 
> PCI core passes "struct device*" as an argument to the .suspend() and
> .resume() callbacks. As the .suspend() work with "struct instance*",
> extract it from "struct device*" using dev_get_drv_data().
> 
> Driver was also using PCI helper functions like pci_save/restore_state(),
> pci_disable/enable_device(), pci_set_power_state() and pci_enable_wake().
> They should not be invoked by the driver.
> 
> Compile-tested only.
> 
> Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
> ---
>  drivers/scsi/megaraid/megaraid_sas_base.c | 61 ++++++-----------------
>  1 file changed, 16 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
> index 00668335c2af..4a6ee7778977 100644
> --- a/drivers/scsi/megaraid/megaraid_sas_base.c
> +++ b/drivers/scsi/megaraid/megaraid_sas_base.c
> @@ -7539,25 +7539,21 @@ static void megasas_shutdown_controller(struct megasas_instance *instance,
>  	megasas_return_cmd(instance, cmd);
>  }
>  
> -#ifdef CONFIG_PM
>  /**
>   * megasas_suspend -	driver suspend entry point
> - * @pdev:		PCI device structure
> - * @state:		PCI power state to suspend routine
> + * @dev:		Device structure
>   */
> -static int
> -megasas_suspend(struct pci_dev *pdev, pm_message_t state)
> +static int __maybe_unused
> +megasas_suspend(struct device *dev)
>  {
> -	struct megasas_instance *instance;
> -
> -	instance = pci_get_drvdata(pdev);
> +	struct megasas_instance *instance = dev_get_drvdata(dev);
>  
>  	if (!instance)
>  		return 0;
>  
>  	instance->unload = 1;
>  
> -	dev_info(&pdev->dev, "%s is called\n", __func__);
> +	dev_info(dev, "%s is called\n", __func__);
>  
>  	/* Shutdown SR-IOV heartbeat timer */
>  	if (instance->requestorId && !instance->skip_heartbeat_timer_del)
> @@ -7579,7 +7575,7 @@ megasas_suspend(struct pci_dev *pdev, pm_message_t state)
>  
>  	tasklet_kill(&instance->isr_tasklet);
>  
> -	pci_set_drvdata(instance->pdev, instance);
> +	dev_set_drvdata(dev, instance);

It *might* be correct to replace "instance->pdev" with "dev", but it's
not obvious and deserves some explanation.  It's true that you can
replace &pdev->dev with dev, but I don't know anything about
instance->dev.

I don't think this change is actually necessary, is it?
"instance->pdev" is still a pci_dev pointer, so pci_set_drvdata()
should work fine.

It looks goofy to use pci_set_drvdata() or dev_set_drvdata() in a
suspend routine, but I didn't bother trying to figure out what's going
on here.

>  	instance->instancet->disable_intr(instance);
>  
>  	megasas_destroy_irqs(instance);
> @@ -7587,48 +7583,28 @@ megasas_suspend(struct pci_dev *pdev, pm_message_t state)
>  	if (instance->msix_vectors)
>  		pci_free_irq_vectors(instance->pdev);
>  
> -	pci_save_state(pdev);
> -	pci_disable_device(pdev);
> -
> -	pci_set_power_state(pdev, pci_choose_state(pdev, state));
> -
>  	return 0;
>  }
>  
>  /**
>   * megasas_resume-      driver resume entry point
> - * @pdev:               PCI device structure
> + * @dev:              Device structure
>   */
> -static int
> -megasas_resume(struct pci_dev *pdev)
> +static int __maybe_unused
> +megasas_resume(struct device *dev)
>  {
>  	int rval;
>  	struct Scsi_Host *host;
> -	struct megasas_instance *instance;
> +	struct megasas_instance *instance = dev_get_drvdata(dev);
>  	u32 status_reg;
>  
> -	instance = pci_get_drvdata(pdev);
> -
>  	if (!instance)
>  		return 0;
>  
>  	host = instance->host;
> -	pci_set_power_state(pdev, PCI_D0);
> -	pci_enable_wake(pdev, PCI_D0, 0);
> -	pci_restore_state(pdev);
> +	device_wakeup_disable(dev);

Shouldn't there be a corresponding device_wakeup_enable() or similar
elsewhere?

Maybe the fact that megasas disables wakeup but never enables it is a
latent bug?

> -	dev_info(&pdev->dev, "%s is called\n", __func__);
> -	/*
> -	 * PCI prepping: enable device set bus mastering and dma mask
> -	 */
> -	rval = pci_enable_device_mem(pdev);
> -
> -	if (rval) {
> -		dev_err(&pdev->dev, "Enable device failed\n");
> -		return rval;
> -	}
> -
> -	pci_set_master(pdev);
> +	dev_info(dev, "%s is called\n", __func__);
>  
>  	/*
>  	 * We expect the FW state to be READY
> @@ -7754,14 +7730,8 @@ megasas_resume(struct pci_dev *pdev)
>  fail_set_dma_mask:
>  fail_ready_state:
>  
> -	pci_disable_device(pdev);
> -
>  	return -ENODEV;
>  }
> -#else
> -#define megasas_suspend	NULL
> -#define megasas_resume	NULL
> -#endif
>  
>  static inline int
>  megasas_wait_for_adapter_operational(struct megasas_instance *instance)
> @@ -7931,7 +7901,7 @@ static void megasas_detach_one(struct pci_dev *pdev)
>  
>  /**
>   * megasas_shutdown -	Shutdown entry point
> - * @device:		Generic device structure
> + * @pdev:		PCI device structure

Looks like an unrelated typo fix?  I would put this in a separate
patch.

>   */
>  static void megasas_shutdown(struct pci_dev *pdev)
>  {
> @@ -8508,6 +8478,8 @@ static const struct file_operations megasas_mgmt_fops = {
>  	.llseek = noop_llseek,
>  };
>  
> +static SIMPLE_DEV_PM_OPS(megasas_pm_ops, megasas_suspend, megasas_resume);
> +
>  /*
>   * PCI hotplug support registration structure
>   */
> @@ -8517,8 +8489,7 @@ static struct pci_driver megasas_pci_driver = {
>  	.id_table = megasas_pci_table,
>  	.probe = megasas_probe_one,
>  	.remove = megasas_detach_one,
> -	.suspend = megasas_suspend,
> -	.resume = megasas_resume,
> +	.driver.pm = &megasas_pm_ops,
>  	.shutdown = megasas_shutdown,
>  };
>  
> -- 
> 2.27.0
> 
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