linux-kernel - RE: [PATCH] nvme-pci: Use non-operational power state instead of D3 on Suspend-to-Idle

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Date:   Wed, 8 May 2019 19:38:50 +0000
From:   <Mario.Limonciello@...l.com>
To:     <kai.heng.feng@...onical.com>, <kbusch@...nel.org>
CC:     <keith.busch@...el.com>, <axboe@...com>, <hch@....de>,
        <sagi@...mberg.me>, <linux-nvme@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] nvme-pci: Use non-operational power state instead of D3
 on Suspend-to-Idle

> -----Original Message-----
> From: Kai-Heng Feng <kai.heng.feng@...onical.com>
> Sent: Wednesday, May 8, 2019 2:30 PM
> To: Keith Busch
> Cc: Keith Busch; axboe@...com; hch@....de; sagi@...mberg.me; linux-
> nvme@...ts.infradead.org; linux-kernel@...r.kernel.org; Limonciello, Mario
> Subject: Re: [PATCH] nvme-pci: Use non-operational power state instead of D3 on
> Suspend-to-Idle
> 
> 
> [EXTERNAL EMAIL]
> 
> at 03:16, Keith Busch <kbusch@...nel.org> wrote:
> 
> > On Thu, May 09, 2019 at 02:59:55AM +0800, Kai-Heng Feng wrote:
> >> +static int nvme_do_resume_from_idle(struct pci_dev *pdev)
> >> +{
> >> +	struct nvme_dev *ndev = pci_get_drvdata(pdev);
> >> +	int result;
> >> +
> >> +	pdev->dev_flags &= ~PCI_DEV_FLAGS_NO_D3;
> >> +	ndev->ctrl.suspend_to_idle = false;
> >> +
> >> +	result = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_ALL_TYPES);
> >> +	if (result < 0)
> >> +		goto out;
> >> +
> >> +	result = nvme_pci_configure_admin_queue(ndev);
> >> +	if (result)
> >> +		goto out;
> >> +
> >> +	result = nvme_alloc_admin_tags(ndev);
> >> +	if (result)
> >> +		goto out;
> >> +
> >> +	ndev->ctrl.max_hw_sectors = NVME_MAX_KB_SZ << 1;
> >> +	ndev->ctrl.max_segments = NVME_MAX_SEGS;
> >> +	mutex_unlock(&ndev->shutdown_lock);
> >
> > This lock was never locked.
> 
> Yea, will fix this.
> 
> >
> > But I think these special suspend/resume routines are too similar to the
> > existing ones, they should just incorporate this feature if we need to
> > do this.
> 
> That’s my original direction, but this requires a new bool to
> nvme_dev_disable(), so it becomes
> static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown, bool
> suspend_to_idle)
> 
> And it starts to get messy.
> 

The existing routines have an implied assumption that firmware will come swinging
with a hammer to control the rails the SSD sits on.
With S2I everything needs to come from the driver side and it really is a
different paradigm.