linux.git/drivers/tty/hvc, branch v4.19-rc2 Linux kernel source tree powerpc/powernv: provide a console flush operation for opal hvc driver 2018-08-20T10:19:54+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:58+00:00 95b861a76c1ded3e89d33a3d9f4552dce22e9875 Provide the flush hv_op for the opal hvc driver. This will flush the firmware console buffers without spinning with interrupts disabled. Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: linuxppc-dev@lists.ozlabs.org Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
Provide the flush hv_op for the opal hvc driver. This will flush the
firmware console buffers without spinning with interrupts disabled.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Merge branch 'topic/hvc' into next 2018-08-13T06:04:10+00:00 Michael Ellerman mpe@ellerman.id.au 2018-08-13T06:04:10+00:00 70b5c4ee8e3bf7ce107d6926d9c7d8ebb68578c2 This branch held some hvc related commits (Hypervisor Virtual Console) so that they could get some wider testing in linux-next before merging. 
This branch held some hvc related commits (Hypervisor Virtual Console)
so that they could get some wider testing in linux-next before merging.
tty: hvc: remove unexplained "just in case" spin delay 2018-07-24T12:09:58+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:52+00:00 cca3d5290ede73b01144aa522910c88b1e02fcef This delay was in the very first OPAL console commit 6.5 years ago, and came from the vio hvc driver. The firmware console has hardened sufficiently to remove it. Reviewed-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
This delay was in the very first OPAL console commit 6.5 years ago,
and came from the vio hvc driver. The firmware console has hardened
sufficiently to remove it.

Reviewed-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
powerpc/powernv: implement opal_put_chars_atomic 2018-07-24T12:09:57+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:51+00:00 17cc1dd4924391b54fb179d0868b89dc96f2ee80 The RAW console does not need writes to be atomic, so relax opal_put_chars to be able to do partial writes, and implement an _atomic variant which does not take a spinlock. This API is used in xmon, so the less locking that is used, the better chance there is that a crash can be debugged. Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
The RAW console does not need writes to be atomic, so relax
opal_put_chars to be able to do partial writes, and implement an
_atomic variant which does not take a spinlock. This API is used
in xmon, so the less locking that is used, the better chance there
is that a crash can be debugged.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
powerpc/powernv: move opal console flushing to udbg 2018-07-24T12:09:57+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:50+00:00 ac4ac788fdadc6b703ff3322de07dee442e08e1c OPAL console writes do not have to synchronously flush firmware / hardware buffers unless they are going through the udbg path. Remove the unconditional flushing from opal_put_chars. Flush if there was no space in the buffer as an optimisation (callers loop waiting for success in that case). udbg flushing is moved to udbg_opal_putc. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
OPAL console writes do not have to synchronously flush firmware /
hardware buffers unless they are going through the udbg path.

Remove the unconditional flushing from opal_put_chars. Flush if
there was no space in the buffer as an optimisation (callers loop
waiting for success in that case). udbg flushing is moved to
udbg_opal_putc.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
tty: hvc: introduce the hv_ops.flush operation for hvc drivers 2018-07-23T10:13:20+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:57+00:00 9f65b81f36e31563c5a5e4df3b3b8bc7550b6030 Use .flush to wait for drivers to flush their console outside of the spinlock, to reduce lock/irq latencies. Flush the hvc console driver after each write, which can help messages make it out to the console after a crash. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
Use .flush to wait for drivers to flush their console outside of
the spinlock, to reduce lock/irq latencies.

Flush the hvc console driver after each write, which can help
messages make it out to the console after a crash.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
tty: hvc: hvc_write() may sleep 2018-07-23T10:12:32+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:56+00:00 550ddadcc7580ec2a6c22d4ed04291bc6e2428fb Rework the hvc_write loop to drop and re-take the spinlock on each iteration, add a cond_resched. Don't bother with an initial hvc_push initially, which makes the logic simpler -- just do a hvc_push on each time around the loop. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
Rework the hvc_write loop to drop and re-take the spinlock on each
iteration, add a cond_resched. Don't bother with an initial hvc_push
initially, which makes the logic simpler -- just do a hvc_push on
each time around the loop.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
tty: hvc: hvc_poll() may sleep 2018-07-23T10:12:12+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:55+00:00 cfb5946b55f1dfd19e042feae1fbff6041e25a98 Introduce points where hvc_poll drops the lock, enables interrupts, and reschedules. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
Introduce points where hvc_poll drops the lock, enables interrupts,
and reschedules.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
tty: hvc: hvc_poll() break hv read loop 2018-07-23T10:11:55+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:54+00:00 ec97eaad1383ab2500fcf9a07ade6044fbcc67f5 Avoid looping with the spinlock held while there is read data being returned from the hv driver. Instead note if the entire size returned by tty_buffer_request_room was read, and request another read poll. This limits the critical section lengths, and provides more even service to other consoles in case there is a pathological condition. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
Avoid looping with the spinlock held while there is read data
being returned from the hv driver. Instead note if the entire
size returned by tty_buffer_request_room was read, and request
another read poll.

This limits the critical section lengths, and provides more
even service to other consoles in case there is a pathological
condition.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
tty: hvc: use mutex instead of spinlock for hvc_structs lock 2018-07-23T10:07:53+00:00 Nicholas Piggin npiggin@gmail.com 2018-04-30T14:55:53+00:00 a9bf5c8a271b9a954709b7ada1bd258f5cadf7ff This allows hvc operations to sleep under the lock. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> 
This allows hvc operations to sleep under the lock.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>