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Junnan Wu 29fb9633bf firmware: arm_scmi: Mark VirtIO ready before registering scmi_virtio_driver 
[ Upstream commit e8faa8a466 ]

After commit 20bda12a0e (“firmware: arm_scmi: Make VirtIO transport a
standalone driver”), the VirtIO transport probes independently. During
scmi_virtio_probe, scmi_probe() is called, which intune invokes
scmi_protocol_acquire() that sends a message over the virtqueue and
waits for a reply.

Previously, DRIVER_OK was only set after scmi_vio_probe, in the core
virtio via virtio_dev_probe(). According to the Virtio spec (3.1 Device
Initialization):
  |  The driver MUST NOT send any buffer available notifications to the
  |  device before setting DRIVER_OK.

Some type-1 hypervisors block available-buffer notifications until the
driver is marked OK. In such cases, scmi_vio_probe stalls in
scmi_wait_for_reply(), and the probe never completes.

Resolve this by setting DRIVER_OK immediately after the device-specific
setup, so scmi_probe() can safely send notifications.

Note after splitting the transports into modules, the probe sequence
changed a bit. We can no longer rely on virtio_device_ready() being
called by the core in virtio_dev_probe(), because scmi_vio_probe()
doesn’t complete until the core SCMI stack runs scmi_probe(), which
immediately issues the initial BASE protocol exchanges.

Fixes: 20bda12a0e ("firmware: arm_scmi: Make VirtIO transport a standalone driver")
Signed-off-by: Junnan Wu <junnan01.wu@samsung.com>
Message-Id: <20250812075343.3201365-1-junnan01.wu@samsung.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-10-15 11:59:56 +02:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.