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

[Vaibhav Gupta <vaibhavgupta40@gmail.com>]

On Tue, Sep 08, 2020 at 12:32:09PM -0500, Bjorn Helgaas wrote:
> 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.
> 
There is no instance->dev . The 'dev' passed dev_set_drvdata() is same
&pdev->dev. The dev pointer used here, points to same value.

pci_get_drvdata() and pci_set_drvdata() invoke dev_get_drvdata() and
dev_set_drvdata() respectively. And they do nothing else. Seems like additional
unnecessary function calls and operations.

We can get rid of these PCI helper functions too.
> >  	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?
> 
Yeah, I guess I sent this patch a lot earlier than we figured this out and
didn't notice it later. I will send v3 for it.
> > -	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.
> 
Okay.
> >   */
> >  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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