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From: Bjorn Helgaas <helgaas@kernel.org>
To: Vaibhav Gupta <vaibhavgupta40@gmail.com>
Cc: Don Brace <don.brace@microsemi.com>,
	Vaibhav Gupta <vaibhav.varodek@gmail.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Hannes Reinecke <hare@suse.com>,
	Bradley Grove <linuxdrivers@attotech.com>,
	linux-scsi@vger.kernel.org,
	Sathya Prakash <sathya.prakash@broadcom.com>,
	esc.storagedev@microsemi.com,
	James Smart <james.smart@broadcom.com>,
	Kashyap Desai <kashyap.desai@broadcom.com>,
	Jack Wang <jinpu.wang@cloud.ionos.com>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Dick Kennedy <dick.kennedy@broadcom.com>,
	Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	John Garry <john.garry@huawei.com>,
	Adam Radford <aradford@gmail.com>,
	Adaptec OEM Raid Solutions <aacraid@microsemi.com>,
	megaraidlinux.pdl@broadcom.com,
	Sreekanth Reddy <sreekanth.reddy@broadcom.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Shivasharan S <shivasharan.srikanteshwara@broadcom.com>,
	MPT-FusionLinux.pdl@broadcom.com, linux-kernel@vger.kernel.org,
	Sumit Saxena <sumit.saxena@broadcom.com>
Subject: Re: [Linux-kernel-mentees] [PATCH v2 01/15] scsi: megaraid_sas: use generic power management
Date: Wed, 9 Sep 2020 11:21:00 -0500	[thread overview]
Message-ID: <20200909162100.GA710627@bjorn-Precision-5520> (raw)
In-Reply-To: <20200909152058.GA14223@gmail.com>

On Wed, Sep 09, 2020 at 08:50:58PM +0530, Vaibhav Gupta wrote:
> On Wed, Sep 09, 2020 at 08:23:32AM -0500, Bjorn Helgaas wrote:
> > On Wed, Sep 09, 2020 at 03:33:15PM +0530, Vaibhav Gupta wrote:
> > > 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.
> > 
> > Sorry, I meant "instance->pdev" here.
> > 
> > > > 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. ...
> > > > 
> > > There is no instance->dev . The 'dev' passed dev_set_drvdata() is
> > > same &pdev->dev. 
> > 
> > Yes, it's true that "dev" here is the same as the "&pdev->dev" we had
> > previously.  But we passed "instance->pdev" (not "pdev") to
> > pci_set_drvdata().  So the question is whether instance->pdev->dev ==
> > dev.
> > 
> > They *might* be the same, but I don't think it's obvious.
> > 
> Yes, they are same.
> driver/pci/pci-driver.c :
> 'dev' is passed as parameter to both pci_device_probe() and pci_pm_suspend()
> From 'dev', pci_device_probe() extracts "struct pci_dev*" and passes it to the
> probe callback of this driver.
> 
> In the proble function - megasas_probe_one()
> :7347	instance->pdev = pdev;
> :7386	pci_set_drvdata(pdev, instance);
> 
> The proble function is using "struct pci_dev*" variable "pdev" provided by core
> and same we replaced &pdev->dev with "struct device *dev".
> 
> So the instance->pdev->dev and 'dev' can only differ if 'dev' passed to
> pci_device_probe() and pci_pm_suspend() are different.

OK.  I think this requires too much analysis for this particular
patch, which is really about deprecating pci_driver.suspend and
.resume.  We want patches to be easily verifiable with a minimum of
extra research.

I would completely support a separate patch to clean this up, though.
The *ideal* thing would be to get rid of the set_drvdata() completely
from the suspend routine.  Doing it in the probe routine should be
enough.

> > > 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.
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  reply	other threads:[~2020-09-09 16:21 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-20 13:34 [Linux-kernel-mentees] [PATCH v2 00/15] scsi: " Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 01/15] scsi: megaraid_sas: " Vaibhav Gupta
2020-09-08 16:57   ` Vaibhav Gupta
2020-09-08 17:32   ` Bjorn Helgaas
2020-09-09 10:03     ` Vaibhav Gupta
2020-09-09 13:23       ` Bjorn Helgaas
2020-09-09 15:20         ` Vaibhav Gupta
2020-09-09 16:21           ` Bjorn Helgaas [this message]
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 02/15] scsi: aacraid: " Vaibhav Gupta
2020-07-23  6:58   ` Balsundar.P--- via Linux-kernel-mentees
2020-09-08 16:58   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 03/15] scsi: aic7xxx: " Vaibhav Gupta
2020-09-08 16:59   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 04/15] scsi: aic79xx: " Vaibhav Gupta
2020-09-08 16:59   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 05/15] scsi: arcmsr: " Vaibhav Gupta
2020-09-08 17:00   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 06/15] scsi: esas2r: " Vaibhav Gupta
2020-09-08 17:01   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 07/15] scsi: hisi_sas_v3_hw: " Vaibhav Gupta
2020-07-21  1:36   ` chenxiang (M)
2020-09-08 17:02   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 08/15] scsi: mpt3sas_scsih: " Vaibhav Gupta
2020-09-08 17:03   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 09/15] scsi: lpfc: " Vaibhav Gupta
2020-09-08 17:03   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 10/15] scsi: pm_8001: " Vaibhav Gupta
2020-07-23  7:02   ` Jinpu Wang
2020-09-08 17:04   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 11/15] scsi: hpsa: " Vaibhav Gupta
2020-07-20 22:23   ` Don.Brace--- via Linux-kernel-mentees
2020-09-08 17:05   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 12/15] scsi: 3w-9xxx: " Vaibhav Gupta
2020-09-08 17:05   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 13/15] scsi: 3w-sas: " Vaibhav Gupta
2020-09-08 17:06   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 14/15] scsi: mvumi: " Vaibhav Gupta
2020-09-08 17:07   ` Vaibhav Gupta
2020-07-20 13:34 ` [Linux-kernel-mentees] [PATCH v2 15/15] scsi: pmcraid: " Vaibhav Gupta
2020-09-08 17:08   ` Vaibhav Gupta
2020-08-17  8:16 ` [Linux-kernel-mentees] [PATCH v2 00/15] scsi: " Vaibhav Gupta
2020-09-08 16:54 ` Vaibhav Gupta

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