firmware: arm_scmi: Use dedicated devices to initialize channels

Refactor channels initialization to use dedicated transport devices
instead of using devices borrowed from the SCMI drivers.

Initialize all channels, as described in the device tree, upfront during
SCMI core stack probe phase and free all of them, including the underlying
devices, when the SCMI core is removed.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221222185049.737625-3-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Simplify chan_available transport operation

SCMI transport operation .chan_available determines in a transport
specific way if an SCMI channel is still available and to be configured.
Such information is derived by analyzing bits of device node in a
transport specific way, all it needs is a device node to operate up on,
not necessarily a full blown device.

Simplify the helper to receive in input a reference to a device_node
instead of a device carrying a pointer to such device_node.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221222185049.737625-2-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Fix virtio channels cleanup on shutdown

When unloading the SCMI core stack module, configured to use the virtio
SCMI transport, LOCKDEP reports the splat down below about unsafe locks
dependencies.

In order to avoid this possible unsafe locking scenario call upfront
virtio_break_device() before getting hold of vioch->lock.

=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
6.1.0-00067-g6b934395ba07-dirty #4 Not tainted
-----------------------------------------------------
rmmod/307 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
ffff000080c510e0 (&dev->vqs_list_lock){+.+.}-{3:3}, at: virtio_break_device+0x28/0x68

and this task is already holding:
ffff00008288ada0 (&channels[i].lock){-.-.}-{3:3}, at: virtio_chan_free+0x60/0x168 [scmi_module]

which would create a new lock dependency:
(&channels[i].lock){-.-.}-{3:3} -> (&dev->vqs_list_lock){+.+.}-{3:3}

but this new dependency connects a HARDIRQ-irq-safe lock:
(&channels[i].lock){-.-.}-{3:3}

... which became HARDIRQ-irq-safe at:
lock_acquire+0x128/0x398
_raw_spin_lock_irqsave+0x78/0x140
scmi_vio_complete_cb+0xb4/0x3b8 [scmi_module]
vring_interrupt+0x84/0x120
vm_interrupt+0x94/0xe8
__handle_irq_event_percpu+0xb4/0x3d8
handle_irq_event_percpu+0x20/0x68
handle_irq_event+0x50/0xb0
handle_fasteoi_irq+0xac/0x138
generic_handle_domain_irq+0x34/0x50
gic_handle_irq+0xa0/0xd8
call_on_irq_stack+0x2c/0x54
do_interrupt_handler+0x8c/0x90
el1_interrupt+0x40/0x78
el1h_64_irq_handler+0x18/0x28
el1h_64_irq+0x64/0x68
_raw_write_unlock_irq+0x48/0x80
ep_start_scan+0xf0/0x128
do_epoll_wait+0x390/0x858
do_compat_epoll_pwait.part.34+0x1c/0xb8
__arm64_sys_epoll_pwait+0x80/0xd0
invoke_syscall+0x4c/0x110
el0_svc_common.constprop.3+0x98/0x120
do_el0_svc+0x34/0xd0
el0_svc+0x40/0x98
el0t_64_sync_handler+0x98/0xc0
el0t_64_sync+0x170/0x174

to a HARDIRQ-irq-unsafe lock:
(&dev->vqs_list_lock){+.+.}-{3:3}

... which became HARDIRQ-irq-unsafe at:
...
lock_acquire+0x128/0x398
_raw_spin_lock+0x58/0x70
__vring_new_virtqueue+0x130/0x1c0
vring_create_virtqueue+0xc4/0x2b8
vm_find_vqs+0x20c/0x430
init_vq+0x308/0x390
virtblk_probe+0x114/0x9b0
virtio_dev_probe+0x1a4/0x248
really_probe+0xc8/0x3a8
__driver_probe_device+0x84/0x190
driver_probe_device+0x44/0x110
__driver_attach+0x104/0x1e8
bus_for_each_dev+0x7c/0xd0
driver_attach+0x2c/0x38
bus_add_driver+0x1e4/0x258
driver_register+0x6c/0x128
register_virtio_driver+0x2c/0x48
virtio_blk_init+0x70/0xac
do_one_initcall+0x84/0x420
kernel_init_freeable+0x2d0/0x340
kernel_init+0x2c/0x138
ret_from_fork+0x10/0x20

other info that might help us debug this:

Possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&dev->vqs_list_lock);
local_irq_disable();
lock(&channels[i].lock);
lock(&dev->vqs_list_lock);
<Interrupt>
lock(&channels[i].lock);

*** DEADLOCK ***
================

Fixes: 42e90eb53bf3f ("firmware: arm_scmi: Add a virtio channel refcount")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221222183823.518856-6-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Fix deferred_tx_wq release on error paths

Use devres to allocate the dedicated deferred_tx_wq polling workqueue so
as to automatically trigger the proper resource release on error path.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 5a3b7185c47c ("firmware: arm_scmi: Add atomic mode support to virtio transport")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221028140833.280091-6-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Fix devres allocation device in virtio transport

SCMI virtio transport device managed allocations must use the main
platform device in devres operations instead of the channel devices.

Cc: Peter Hilber <peter.hilber@opensynergy.com>
Fixes: 46abe13b5e3d ("firmware: arm_scmi: Add virtio transport")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221028140833.280091-5-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Add atomic mode support to virtio transport

Add support for .mark_txdone and .poll_done transport operations to SCMI
VirtIO transport as pre-requisites to enable atomic operations.

Add a Kernel configuration option to enable SCMI VirtIO transport polling
and atomic mode for selected SCMI transactions while leaving it default
disabled.

Link: https://lore.kernel.org/r/20220217131234.50328-4-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Skalkin <igor.skalkin@opensynergy.com>
Cc: Peter Hilber <peter.hilber@opensynergy.com>
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Review virtio free_list handling

Add a new spinlock dedicated to the access of the TX free list and a couple
of helpers to get and put messages back and forth from the free_list.

Link: https://lore.kernel.org/r/20220217131234.50328-3-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Skalkin <igor.skalkin@opensynergy.com>
Cc: Peter Hilber <peter.hilber@opensynergy.com>
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Add a virtio channel refcount

Currently SCMI VirtIO channels are marked with a ready flag and related
lock to track channel lifetime and support proper synchronization at
shutdown when virtqueues have to be stopped.

This leads to some extended spinlocked sections with IRQs off on the RX
path to keep hold of the ready flag and does not scale well especially when
SCMI VirtIO polling mode will be introduced.

Add an SCMI VirtIO channel dedicated refcount to track active users on both
the TX and the RX path and properly enforce synchronization and cleanup at
shutdown, inhibiting further usage of the channel once freed.

Link: https://lore.kernel.org/r/20220217131234.50328-2-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Skalkin <igor.skalkin@opensynergy.com>
Cc: Peter Hilber <peter.hilber@opensynergy.com>
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Make virtio Version_1 compliance optional

Introduce a compilation option to disable strict enforcement of compliance
against VirtIO Version_1 backends, so as to allow to support also Legacy
VirtIO devices implementations.

Link: https://lore.kernel.org/r/20211115102910.7639-1-cristian.marussi@arm.com
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Review some virtio log messages

Be more verbose avoiding to use _once flavour of dev_info/_err/_notice.
Remove usage of __func_ to identify which vqueue is referred in some error
messages and explicitly name the TX/RX vqueue.

Link: https://lore.kernel.org/r/20210916103336.7243-1-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

virtio: wrap config->reset calls

This will enable cleanups down the road.
The idea is to disable cbs, then add "flush_queued_cbs" callback
as a parameter, this way drivers can flush any work
queued after callbacks have been disabled.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20211013105226.20225-1-mst@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

firmware: arm_scmi: Fix null de-reference on error path

During channel setup a failure in the call of scmi_vio_feed_vq_rx() leads
to an attempt to access a dev pointer by dereferencing vioch->cinfo at
a time when vioch->cinfo has still to be initialized.

Fix it by providing the device reference directly to scmi_vio_feed_vq_rx.

Link: https://lore.kernel.org/r/20211112180705.41601-1-cristian.marussi@arm.com
Fixes: 46abe13b5e3db ("firmware: arm_scmi: Add virtio transport")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Add proper barriers to scmi virtio device

Only one single SCMI Virtio device is currently supported by this driver
and it is referenced using a static global variable which is initialized
once for all during probing and nullified at virtio device removal.

Add proper SMP barriers to protect accesses to such device reference to
ensure that the initialzation state of such device is correctly observed by
all PEs at any time.

Return -EBUSY, instead of -EINVAL, and a descriptive error message if more
than one SCMI Virtio device is ever found and probed.

Link: https://lore.kernel.org/r/20210916103336.7243-3-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Simplify spinlocks in virtio transport

Remove unneeded nested irqsave/irqrestore spinlocks.
Add also a few descriptive comments to explain better the system behaviour
at shutdown time.

Link: https://lore.kernel.org/r/20210916103336.7243-2-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Remove __exit annotation

virtio_scmi_exit() is only called from __exit function, so the annotation
is correct, but when the driver is built-in, the section gets discarded
and the reference from a callback pointer causes a link-time error:

`virtio_scmi_exit' referenced in section `.rodata' of drivers/firmware/arm_scmi/virtio.o:
defined in discarded section `.exit.text' of drivers/firmware/arm_scmi/virtio.o

I could not figure out a better workaround, so let's just remove that
annotation even if it wastes a couple of bytes in .text.

Link: https://lore.kernel.org/r/20210920100301.1466486-2-arnd@kernel.org
Fixes: 46abe13b5e3d ("firmware: arm_scmi: Add virtio transport")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Fix boolconv.cocci warnings

drivers/firmware/arm_scmi/virtio.c:225:40-45: WARNING: conversion to bool not needed here

Remove unneeded conversion to bool

Semantic patch information:
Relational and logical operators evaluate to bool,
explicit conversion is overly verbose and unneeded.

Generated by: scripts/coccinelle/misc/boolconv.cocci

Link: https://lore.kernel.org/r/20210807173127.GA43248@a24dbc127934
CC: Igor Skalkin <igor.skalkin@opensynergy.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: arm_scmi: Add virtio transport

This transport enables communications with an SCMI platform through virtio;
the SCMI platform will be represented by a virtio device.

Implement an SCMI virtio driver according to the virtio SCMI device spec
[1]. Virtio device id 32 has been reserved for the SCMI device [2].

The virtio transport has one Tx channel (virtio cmdq, A2P channel) and
at most one Rx channel (virtio eventq, P2A channel).

The following feature bit defined in [1] is not implemented:
VIRTIO_SCMI_F_SHARED_MEMORY.

The number of messages which can be pending simultaneously is restricted
according to the virtqueue capacity negotiated at probing time.

As soon as Rx channel message buffers are allocated or have been read
out by the arm-scmi driver, feed them back to the virtio device.

Since some virtio devices may not have the short response time exhibited
by SCMI platforms using other transports, set a generous response
timeout.

SCMI polling mode is not supported by this virtio transport since deemed
meaningless: polling mode operation is offered by the SCMI core to those
transports that could not provide a completion interrupt on the TX path,
which is never the case for virtio whose core callbacks can easily call
into core scmi_rx_callback upon messages reception.

[1] https://github.com/oasis-tcs/virtio-spec/blob/master/virtio-scmi.tex
[2] https://www.oasis-open.org/committees/ballot.php?id=3496

Link: https://lore.kernel.org/r/20210803131024.40280-16-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
Co-developed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
[ Peter: Adapted patch for submission to upstream. ]
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
[ Cristian: simplified driver logic, changed link_supplier and channel
available/setup logic, removed dummy callbacks ]
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>