uart: Add primitive noise filtering on RX

A long cable attached to the UART can act as an antenna if disconnected
from the other end. This can cause noise on the receive side, possibly
as reflectio

uart: Add primitive noise filtering on RX

A long cable attached to the UART can act as an antenna if disconnected
from the other end. This can cause noise on the receive side, possibly
as reflections from the transmit side, leading to an interrupt storm.
Filter this by adding a threshold of received characters without TX
ready, above which characters are dropped. This is disabled by default,
but has been tested with a threshold of 1000+. A high threshold is
recommended to avoid dropping characters during, for instance, a large
copy/paste from the other end.

Sponsored by: Juniper Networks, Inc.

show more ...

uart(4): Honor hardware state of NS8250-class for tsw_busy

In 9750d9e5, I brought the equivalent of the TS_BUSY flag back in a
mostly hardware-agnostic way in order to fix tty_drain() and, thus,
TIO

uart(4): Honor hardware state of NS8250-class for tsw_busy

In 9750d9e5, I brought the equivalent of the TS_BUSY flag back in a
mostly hardware-agnostic way in order to fix tty_drain() and, thus,
TIOCDRAIN for UARTs with TX FIFOs. This proved to be sufficient for
fixing the regression reported. So in light of the release cycle of
FreeBSD 10.3, I decided that this change was be good enough for the
time being and opted to go with the smallest possible yet generic
(for all UARTs driven by uart(4)) solution addressing the problem at
hand.

However, at least for the NS8250-class the above isn't a complete
fix as these UARTs only trigger an interrupt when the TX FIFO became
empty. At this point, there still can be an outstanding character
left in the transmit shift register as indicated via the LSR. Thus,
this change adds the 3rd (besides the tty(4) and generic uart(4) bits)
part I had in my tree ever since, adding a uart_txbusy method to be
queried in addition for tsw_busy and hooking it up as appropriate
for the NS8250-class.

As it turns out, the exact equivalent of this 3rd part later on was
implemented for uftdi(4) in 9ad221a5.

While at it, explain the rational behind the deliberately missing
locking in uart_tty_busy() (also applying to the generic sc_txbusy
testing already present).

show more ...

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

show more ...

uart: clean up empty lines in .c and .h files

uart: Add primitive noise filtering on RX

A long cable attached to the UART can act as an antenna if disconnected
from the other end. This can cause noise on the receive side, possibly
as reflectio

uart: Add primitive noise filtering on RX

A long cable attached to the UART can act as an antenna if disconnected
from the other end. This can cause noise on the receive side, possibly
as reflections from the transmit side, leading to an interrupt storm.
Filter this by adding a threshold of received characters without TX
ready, above which characters are dropped. This is disabled by default,
but has been tested with a threshold of 1000+. A high threshold is
recommended to avoid dropping characters during, for instance, a large
copy/paste from the other end.

Sponsored by: Juniper Networks, Inc.

show more ...

uart(4): Honor hardware state of NS8250-class for tsw_busy

In 9750d9e5, I brought the equivalent of the TS_BUSY flag back in a
mostly hardware-agnostic way in order to fix tty_drain() and, thus,
TIO

uart(4): Honor hardware state of NS8250-class for tsw_busy

In 9750d9e5, I brought the equivalent of the TS_BUSY flag back in a
mostly hardware-agnostic way in order to fix tty_drain() and, thus,
TIOCDRAIN for UARTs with TX FIFOs. This proved to be sufficient for
fixing the regression reported. So in light of the release cycle of
FreeBSD 10.3, I decided that this change was be good enough for the
time being and opted to go with the smallest possible yet generic
(for all UARTs driven by uart(4)) solution addressing the problem at
hand.

However, at least for the NS8250-class the above isn't a complete
fix as these UARTs only trigger an interrupt when the TX FIFO became
empty. At this point, there still can be an outstanding character
left in the transmit shift register as indicated via the LSR. Thus,
this change adds the 3rd (besides the tty(4) and generic uart(4) bits)
part I had in my tree ever since, adding a uart_txbusy method to be
queried in addition for tsw_busy and hooking it up as appropriate
for the NS8250-class.

As it turns out, the exact equivalent of this 3rd part later on was
implemented for uftdi(4) in 9ad221a5.

While at it, explain the rational behind the deliberately missing
locking in uart_tty_busy() (also applying to the generic sc_txbusy
testing already present).

show more ...

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

show more ...

uart: clean up empty lines in .c and .h files

sys/dev: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error

sys/dev: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

show more ...

MFC @ r266724

An SVM update will follow this.

Merge head

IFC @264767

Merge head up to r262222 (last merge was incomplete).

MFH@260917.

MFH: Tracking commit (r260891)

Sponsored by: The FreeBSD Foundation

Introduce grab and ungrab upcalls. When the kernel desires to grab the
console, it calls the grab functions. These functions should turn off
the RX interrupts, and any others that interfere. This mak

Introduce grab and ungrab upcalls. When the kernel desires to grab the
console, it calls the grab functions. These functions should turn off
the RX interrupts, and any others that interfere. This makes mountroot
prompt work again. If there's more generalized need other than
prompting, many of these routines should be expanded to do those new
things.

Should have been part of r260889, but waasn't due to command line typo.

Reviewed by: bde (with reservations)

show more ...

Merge head r233826 through r256722.

IFC @256277

Approved by: ken (mentor)

IFC @ r255692

Comment out IA32_MISC_ENABLE MSR access - this doesn't exist on AMD.
Need to sort out how arch-specific MSRs will be handled.

Merge from head

IFC @ r255209

Make the uart ns8250 high-level interface public rather than static.
This makes it easier to implement new drivers which are "mostly ns8250"
but with some small difference such as needing to enable c

Make the uart ns8250 high-level interface public rather than static.
This makes it easier to implement new drivers which are "mostly ns8250"
but with some small difference such as needing to enable clocks or poke
a non-standard register at probe or attach time.

show more ...

sys/dev: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error

sys/dev: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

show more ...