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Date: Mon, 16 Dec 2024 17:23:03 +0100
From: Christoph Hellwig <hch@lst.de>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Bjorn Helgaas <helgaas@kernel.org>, kbusch@kernel.org,
	axboe@kernel.dk, sagi@grimberg.me, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	andersson@kernel.org, konradybcio@kernel.org,
	Len Brown <len.brown@intel.com>, linux-pm@vger.kernel.org
Subject: Re: [PATCH] nvme-pci: Shutdown the device if D3Cold is allowed by
 the user
Message-ID: <20241216162303.GA26434@lst.de>
References: <20241205232900.GA3072557@bhelgaas> <20241209143821.m4dahsaqeydluyf3@thinkpad> <20241212055920.GB4825@lst.de> <13662231.uLZWGnKmhe@rjwysocki.net> <CAPDyKFrxEjHFB6B2r7JbryYY6=E4CxX_xTmLDqO6+26E+ULz6A@mail.gmail.com> <20241212151354.GA7708@lst.de> <CAJZ5v0gUpDw_NjTDtHGCUnKK0C+x0nrW6mP0tHQoXsgwR2RH8g@mail.gmail.com> <20241214063023.4tdvjbqd2lrylb7o@thinkpad>
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On Sat, Dec 14, 2024 at 12:00:23PM +0530, Manivannan Sadhasivam wrote:
> We need a PM core API that tells the device drivers when it is safe to powerdown
> the devices. The usecase here is with PCIe based NVMe devices but the problem is
> applicable to other devices as well.

Maybe I'm misunderstanding things, but I think the important part is
to indicate when a suspend actually MUST put the device into D3.  Because
doing that should always be safe, but not always optimal.