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From: Keith Busch <kbusch@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: "Busch, Keith" <keith.busch@intel.com>,
	Sagi Grimberg <sagi@grimberg.me>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	Rafael Wysocki <rafael@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	linux-pm <linux-pm@vger.kernel.org>,
	Mario Limonciello <Mario.Limonciello@dell.com>,
	Kai Heng Feng <kai.heng.feng@canonical.com>
Subject: Re: [PATCH] nvme/pci: Use host managed power state for suspend
Date: Mon, 13 May 2019 07:36:11 -0600	[thread overview]
Message-ID: <20190513133611.GA15318@localhost.localdomain> (raw)
In-Reply-To: <20190511072258.GB14764@lst.de>

On Sat, May 11, 2019 at 12:22:58AM -0700, Christoph Hellwig wrote:
> A couple nitpicks, mostly leftover from the previous iteration
> (I didn't see replies to those comments from you, despite seeing
> a reply to my mail, assuming it didn't get lost):

I thought you just meant the freeze/unfreeze sequence. I removed that
part entirely, but yes, I can move all of this from the core. I will
just need to export 'nvme_set_features'
 
> > +int nvme_set_power(struct nvme_ctrl *ctrl, unsigned ps)
> > +{
> > +	return nvme_set_features(ctrl, NVME_FEAT_POWER_MGMT, ps, NULL, 0, NULL);
> > +}
> > +EXPORT_SYMBOL_GPL(nvme_set_power);
> > +
> > +int nvme_get_power(struct nvme_ctrl *ctrl, u32 *result)
> > +{
> > +	struct nvme_command c;
> > +	union nvme_result res;
> > +	int ret;
> > +
> > +	if (!result)
> > +		return -EINVAL;
> > +
> > +	memset(&c, 0, sizeof(c));
> > +	c.features.opcode = nvme_admin_get_features;
> > +	c.features.fid = cpu_to_le32(NVME_FEAT_POWER_MGMT);
> > +
> > +	ret = __nvme_submit_sync_cmd(ctrl->admin_q, &c, &res,
> > +			NULL, 0, 0, NVME_QID_ANY, 0, 0, false);
> > +	if (ret >= 0)
> > +		*result = le32_to_cpu(res.u32);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(nvme_get_power);
> 
> At this point I'd rather see those in the PCIe driver.  While the
> power state feature is generic in the spec I don't see it actually
> being used anytime anywhere else any time soon.
> 
> But maybe we can add a nvme_get_features helper ala nvme_set_features
> in the core to avoid a little boilerplate code for the future?

Sounds good.
 
> > +	ret = nvme_set_power(&dev->ctrl, dev->ctrl.npss);
> > +	if (ret < 0)
> > +		return ret;
> 
> I can't find any wording in the spec that guarantees the highest
> numerical power state is the deepest.  But maybe I'm just missing
> something as such an ordering would be really helpful?

I actually only noticed APST made this assumption, and I had to search
the spec to see where it calls this out. It is in section 8.4:

  Power states are contiguously numbered starting with zero such that
  each subsequent power state consumes less than or equal to the maximum
  power consumed in the previous state.

> >  static int nvme_suspend(struct device *dev)
> >  {
> >  	struct pci_dev *pdev = to_pci_dev(dev);
> >  	struct nvme_dev *ndev = pci_get_drvdata(pdev);
> >  
> > +	/*
> > +	 * Try to use nvme if the device supports host managed power settings
> > +	 * and platform firmware is not involved.
> > +	 */
> 
> This just comments that what, but I think we need a why here as the
> what is fairly obvious..

Sounds good.

  parent reply	other threads:[~2019-05-13 13:41 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-10 21:29 Keith Busch
2019-05-11  0:52 ` Mario.Limonciello
2019-05-13 14:24   ` Mario.Limonciello
2019-05-13 14:37     ` Christoph Hellwig
2019-05-13 14:43       ` Mario.Limonciello
2019-05-13 14:54         ` Christoph Hellwig
2019-05-13 14:55         ` Keith Busch
2019-05-13 15:05           ` Mario.Limonciello
2019-05-13 15:04             ` Keith Busch
2019-05-14  8:04               ` Rafael J. Wysocki
2019-05-14 22:16                 ` Keith Busch
2019-05-15  9:00                   ` Rafael J. Wysocki
2019-05-13 14:37     ` Keith Busch
2019-05-13 14:54       ` Mario.Limonciello
2019-05-13 14:57         ` Christoph Hellwig
2019-05-13 15:16           ` Keith Busch
2019-05-13 17:16             ` Kai-Heng Feng
2019-05-13 18:16               ` Keith Busch
2019-05-13 18:01           ` Mario.Limonciello
2019-05-14  6:11             ` Christoph Hellwig
2019-05-11  1:33 ` Edmund Nadolski
2019-05-11  7:22 ` Christoph Hellwig
2019-05-12 14:34   ` Sagi Grimberg
2019-05-13 13:36   ` Keith Busch [this message]
2019-05-12  6:06 ` Chaitanya Kulkarni
2019-05-12 14:30   ` Minwoo Im
2019-05-12 15:20     ` Chaitanya Kulkarni
2019-05-13 13:47   ` Keith Busch

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