[RFC PATCH v1 4/4] virtio-mmio: wire up noirq system sleep PM callbacks

[Sungho Bae <baver.bae@gmail.com>]

From: Sungho Bae <baver.bae@lge.com>

Implement the transport side of noirq system-sleep PM for virtio-mmio:

 - vm_reset_vqs(): iterate all virtqueues, call virtqueue_reinit_vring()
   to reset the vring state in place, then reprogram the MMIO queue
   registers (QUEUE_SEL, QUEUE_NUM, descriptor/avail/used addresses,
   QUEUE_READY) so the device can use the same rings immediately after
   restore.  No memory is allocated or freed.

 - virtio_mmio_freeze_noirq() / virtio_mmio_restore_noirq(): thin
   wrappers that forward to the virtio core noirq helpers.  The
   restore_noirq path also writes GUEST_PAGE_SIZE for legacy (v1)
   devices, matching the existing restore callback.

 - Wire vm_reset_vqs into virtio_mmio_config_ops and register the
   noirq callbacks via SET_NOIRQ_SYSTEM_SLEEP_PM_OPS().

With this in place, a virtio-mmio driver can implement freeze_noirq /
restore_noirq to participate in the noirq PM phase, enabling use cases
such as virtio-clock or virtio-regulator that must be operational
before other devices are restored.

Signed-off-by: Sungho Bae <baver.bae@lge.com>
---
 drivers/virtio/virtio_mmio.c | 79 ++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 595c2274fbb5..7bf193ba4173 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -336,6 +336,65 @@ static void vm_del_vqs(struct virtio_device *vdev)
 	free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
 }
 
+static int vm_reset_vqs(struct virtio_device *vdev)
+{
+	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
+	struct virtqueue *vq;
+
+	virtio_device_for_each_vq(vdev, vq) {
+		unsigned int num = virtqueue_get_vring_size(vq);
+
+		virtqueue_reinit_vring(vq);
+
+		writel(vq->index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
+		writel(num, vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
+
+		if (vm_dev->version == 1) {
+			u64 q_pfn = virtqueue_get_desc_addr(vq) >> PAGE_SHIFT;
+
+			/*
+			 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have
+			 * something that doesn't fit in 32bit, fail the setup
+			 * rather than pretending to be successful.
+			 */
+			if (q_pfn >> 32) {
+				dev_err(&vdev->dev,
+					"platform bug: legacy virtio-mmio must not be used with RAM above 0x%llxGB\n",
+					0x1ULL << (32 + PAGE_SHIFT - 30));
+				return -E2BIG;
+			}
+
+			writel(PAGE_SIZE,
+			       vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
+			writel(q_pfn, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+		} else {
+			u64 addr;
+
+			addr = virtqueue_get_desc_addr(vq);
+			writel((u32)addr,
+			       vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
+			writel((u32)(addr >> 32),
+			       vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
+
+			addr = virtqueue_get_avail_addr(vq);
+			writel((u32)addr,
+			       vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
+			writel((u32)(addr >> 32),
+			       vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
+
+			addr = virtqueue_get_used_addr(vq);
+			writel((u32)addr,
+			       vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
+			writel((u32)(addr >> 32),
+			       vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
+
+			writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
+		}
+	}
+
+	return 0;
+}
+
 static void vm_synchronize_cbs(struct virtio_device *vdev)
 {
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
@@ -528,6 +587,7 @@ static const struct virtio_config_ops virtio_mmio_config_ops = {
 	.reset		= vm_reset,
 	.find_vqs	= vm_find_vqs,
 	.del_vqs	= vm_del_vqs,
+	.reset_vqs	= vm_reset_vqs,
 	.get_features	= vm_get_features,
 	.finalize_features = vm_finalize_features,
 	.bus_name	= vm_bus_name,
@@ -553,8 +613,27 @@ static int virtio_mmio_restore(struct device *dev)
 	return virtio_device_restore(&vm_dev->vdev);
 }
 
+static int virtio_mmio_freeze_noirq(struct device *dev)
+{
+	struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);
+
+	return virtio_device_freeze_noirq(&vm_dev->vdev);
+}
+
+static int virtio_mmio_restore_noirq(struct device *dev)
+{
+	struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);
+
+	if (vm_dev->version == 1)
+		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
+
+	return virtio_device_restore_noirq(&vm_dev->vdev);
+}
+
 static const struct dev_pm_ops virtio_mmio_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(virtio_mmio_freeze, virtio_mmio_restore)
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(virtio_mmio_freeze_noirq,
+				      virtio_mmio_restore_noirq)
 };
 #endif
 
-- 
2.34.1