linux-kernel - [PATCH V2 2/2] drivers/nvme: Add support for ACPI StorageD3Enable property

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Message-Id: <20200612204820.20111-3-david.e.box@linux.intel.com>
Date:   Fri, 12 Jun 2020 13:48:20 -0700
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     shyjumon.n@...el.com, rjw@...ysocki.net, lenb@...nel.org,
        bhelgaas@...gle.com, dan.j.williams@...el.com, kbusch@...nel.org,
        axboe@...com, hch@....de, sagi@...mberg.me
Cc:     "David E. Box" <david.e.box@...ux.intel.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-nvme@...ts.infradead.org
Subject: [PATCH V2 2/2] drivers/nvme: Add support for ACPI StorageD3Enable property

This patch implements a solution for a BIOS hack used on some currently
shipping Intel systems to address issues with power management policy
decisions concerning PCIe NVMe drives. Some newer Intel platforms, like
some Comet Lake systems, require that PCIe devices use D3 when doing
suspend-to-idle in order to allow the platform to realize maximum power
savings. This is particularly needed to support ATX power supply shutdown
on desktop systems. In order to ensure this happens for root ports with
storage devices, Microsoft apparently created this ACPI _DSD property as a
way to override their driver policy. To my knowledge this property has not
been discussed with the NVME specification body.

Though the solution is not ideal, it addresses a problem that also affects
Linux since the NVMe driver's default policy of using NVMe APST during
suspend-to-idle would lead to higher power consumption for these platforms.

The patch uses the previously added pci_acpi_storage_d3 function to check
for the StorageD3Enable property during probe and enables D3 as a quirk if
set.  It also provides a 'noacpi' module parameter to allow skipping the
quirk if needed.

Tested on:
PM961 NVMe SED Samsung 512GB
INTEL SSDPEKKF512G8

Link: https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/power-management-for-storage-hardware-devices-intro
Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
---
 drivers/nvme/host/pci.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 4e79e412b276..427505c47e79 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -78,6 +78,10 @@ static unsigned int poll_queues;
 module_param(poll_queues, uint, 0644);
 MODULE_PARM_DESC(poll_queues, "Number of queues to use for polled IO.");

+static bool noacpi;
+module_param(noacpi, bool, 0444);
+MODULE_PARM_DESC(noacpi, "disable all acpi bios quirks");
+
 struct nvme_dev;
 struct nvme_queue;

@@ -2777,6 +2781,16 @@ static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id)

 	quirks |= check_vendor_combination_bug(pdev);

+	if (!noacpi && pci_acpi_storage_d3(pdev)) {
+		/*
+		 * Some systems use a bios work around to ask for D3 on
+		 * platforms that support kernel managed suspend.
+		 */
+		dev_info(&pdev->dev,
+			 "platform quirk: setting simple suspend\n");
+		quirks |= NVME_QUIRK_SIMPLE_SUSPEND;
+	}
+
 	/*
 	 * Double check that our mempool alloc size will cover the biggest
 	 * command we support.
-- 
2.20.1