[Qemu-devel] [Bug 1753314] [NEW] UART in sabrelite machine simulation doesn't work with VxWorks 7

[Qemu-devel] [Bug 1753314] [NEW] UART in sabrelite machine simulation doesn't work with VxWorks 7

[Bill Paul]

Public bug reported:

The imx_serial.c driver currently implements only partial support for
the i.MX6 UART hardware. (I understand it's a work in progress and
that's fine.) dIn particular, it does not implement support for the
Transmit Complete Interrupt Enable bit in the UCR4 register. The VxWorks
7 i.MX6 serial driver depends on the behavior of this bit in actual
hardware in order to send characters through the UART correctly. The
result is that with the current machine model, VxWorks will boot and run
in QEMU but it's unable to print any characters to the console serial
port.

I have produced a small patch for the imx_serial.c module to make it
nominally functional with VxWorks 7. It works well enough to allow the
boot banner to appear and for the user to interact with the target
shell.

I'm not submitting this as a patch to the development list as I'm not
fully certain it complies with the hardware spec and doesn't break any
other functionality. I would prefer if the maintainer (or someone)
reviewed it for any issues/refinements first.

I'm attaching the patch to this bug report. A copy can also be obtained
from:

http://people.freebsd.org/~wpaul/qemu/imx_serial.zip

This patch was generated against QEMU 2.11.0 but also works with QEMU
2.11.1.

My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
2.11.0/2.11.11 built from source.

** Affects: qemu
     Importance: Undecided
         Status: New


** Tags: arm sabrelite uart

** Patch added: "Patch for imx_serial.c/h to make it work with VxWorks"
   https://bugs.launchpad.net/bugs/1753314/+attachment/5069246/+files/imx_serial.zip

** Summary changed:

- UART in sabrelite machine simulation doesn't work wth VxWorks
+ UART in sabrelite machine simulation doesn't work with VxWorks 7

** Description changed:

  The imx_serial.c driver currently implements only partial support for
- the i.MX6 UART hardware. In particular, it does not implement support
- for the Transmit Complete Interrupt Enable bit in the UCR4 register. The
- VxWorks 7 i.MX6 serial driver depends on the behavior of this bit in
- actual hardware in order to send characters through the UART correctly.
- The result is that with the current machine model, VxWorks will boot and
- run in QEMU but it's unable to print any characters to the console
- serial port.
+ the i.MX6 UART hardware. (I understand it's a work in progress and
+ that's fine.) In particular, it does not implement support for the
+ Transmit Complete Interrupt Enable bit in the UCR4 register. The VxWorks
+ 7 i.MX6 serial driver depends on the behavior of this bit in actual
+ hardware in order to send characters through the UART correctly. The
+ result is that with the current machine model, VxWorks will boot and run
+ in QEMU but it's unable to print any characters to the console serial
+ port.
  
  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.
  
  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.
  
  I'm attaching the patch to this bug report. A copy can also be obtained
  from:
  
  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip
  
  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.

** Description changed:

  The imx_serial.c driver currently implements only partial support for
  the i.MX6 UART hardware. (I understand it's a work in progress and
- that's fine.) In particular, it does not implement support for the
+ that's fine.) dIn particular, it does not implement support for the
  Transmit Complete Interrupt Enable bit in the UCR4 register. The VxWorks
  7 i.MX6 serial driver depends on the behavior of this bit in actual
  hardware in order to send characters through the UART correctly. The
  result is that with the current machine model, VxWorks will boot and run
  in QEMU but it's unable to print any characters to the console serial
  port.
  
  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.
  
  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.
  
  I'm attaching the patch to this bug report. A copy can also be obtained
  from:
  
  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip
  
  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.
+ 
+ My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
+ 2.11.0/2.11.11 built from source.

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Title:
  UART in sabrelite machine simulation doesn't work with VxWorks 7

Status in QEMU:
  New

Bug description:
  The imx_serial.c driver currently implements only partial support for
  the i.MX6 UART hardware. (I understand it's a work in progress and
  that's fine.) dIn particular, it does not implement support for the
  Transmit Complete Interrupt Enable bit in the UCR4 register. The
  VxWorks 7 i.MX6 serial driver depends on the behavior of this bit in
  actual hardware in order to send characters through the UART
  correctly. The result is that with the current machine model, VxWorks
  will boot and run in QEMU but it's unable to print any characters to
  the console serial port.

  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.

  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.

  I'm attaching the patch to this bug report. A copy can also be
  obtained from:

  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip

  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.

  My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
  2.11.0/2.11.11 built from source.

To manage notifications about this bug go to:
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[Qemu-devel] [Bug 1753314] Re: UART in sabrelite machine simulation doesn't work with VxWorks 7

[Peter Maydell]

Hi. Thanks for this patch. I've had a quick look at it against the imx
datasheet, and here are my comments:

* Firstly, we can't do anything with this patch without a Signed-off-by:
line from you. In QEMU's process this is how people submitting code
state that you're legally OK to contribute the code under QEMU's license
and for it to go into QEMU.

 * Secondly, it would be very helpful if you could send patches as a
simple patch format, rather than as a zipfile, and to the QEMU mailing
list. https://wiki.qemu.org/Contribute/SubmitAPatch has our guidelines
on this.

 * Simply adding a new VMSTATE_UINT32() field will break migration. It's
better to put the new field into its own vmstate subsection so that this
doesn't happen; see docs/devel/migration.rst. If we don't care about
cross-version migration we could just bump the
version_id/minimum_version_id fields.

 * If you run scripts/checkpatch.pl over your patch it should warn you
about minor coding style issues. For instance we prefer all if()
statements to use {}, even if there's only one line in them.

 * Your change to imx_update() does this:
+    if (s->ucr4 & UCR4_TXEN)
+        flags |= USR1_TRDY;

but that isn't what the spec says UCR4_TXEN does; it says we raise an
interrupt only if UCR4_TXEN and USR2_TXDC are both high.

 * the imx_update() function is already rather confused in how it
handles the 'flags' variable, and this change extends that confusion.
The function is trying to treat 'flags' as a single set of interrupt
flag bits, but the device doesn't actually have a single unified set of
interrupt flags like that, they're spread over UTS and USR1 and USR2.
The code as it is looks odd -- should USR1.TXMPTYEN == 0 really suppress
USR1_TRDY interrupts ? I suspect this is a bug, and we should also clean
things up to make 'flags' be a bool.

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Title:
  UART in sabrelite machine simulation doesn't work with VxWorks 7

Status in QEMU:
  New

Bug description:
  The imx_serial.c driver currently implements only partial support for
  the i.MX6 UART hardware. (I understand it's a work in progress and
  that's fine.) dIn particular, it does not implement support for the
  Transmit Complete Interrupt Enable bit in the UCR4 register. The
  VxWorks 7 i.MX6 serial driver depends on the behavior of this bit in
  actual hardware in order to send characters through the UART
  correctly. The result is that with the current machine model, VxWorks
  will boot and run in QEMU but it's unable to print any characters to
  the console serial port.

  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.

  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.

  I'm attaching the patch to this bug report. A copy can also be
  obtained from:

  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip

  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.

  My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
  2.11.0/2.11.11 built from source.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1753314/+subscriptions

[Qemu-devel] [Bug 1753314] Re: UART in sabrelite machine simulation doesn't work with VxWorks 7

[Bill Paul]

As I said before:

"I'm not submitting this as a patch to the development list as I'm not
fully certain it complies with the hardware spec and doesn't break any
other functionality."

What I'm trying to say here is that while I may have been able to cobble
together a hack to make the UART nominally compatible with VxWorks, I do
not understand the hardware or QEMU well enough to really fix this the
right way. Even with my hack, every once in a while when printing lots
of data on the console, the output from the UART will stall unless I
press a key on the serial port, and I don't know why it does that. I did
try to investigate it a little but wasn't able to make much progress.
(My suspicion is that it has something to do with the fact that the
imx_serial module doesn't implement FIFO support, but even if that's
true I don't know how to fix it.)

Even so, I figured it was still worth it to attach my changes to the bug
report so that somebody who is better at this than me could use it as a
starting point, and so that anybody else who might want to experiment
with VxWorks using the QEMU sabrelite machine model wouldn't be totally
stuck like I was.

In short, the changes I made are good enough for my own needs (the
output stalls don't happen often enough to really bother me), but
they're not a fully debugged fix. That's why I filed a bug report
instead of just submitting a patch in the first place: I wanted somebody
sexier than me to create a fully debugged fix.

-- 
You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1753314

Title:
  UART in sabrelite machine simulation doesn't work with VxWorks 7

Status in QEMU:
  New

Bug description:
  The imx_serial.c driver currently implements only partial support for
  the i.MX6 UART hardware. (I understand it's a work in progress and
  that's fine.) dIn particular, it does not implement support for the
  Transmit Complete Interrupt Enable bit in the UCR4 register. The
  VxWorks 7 i.MX6 serial driver depends on the behavior of this bit in
  actual hardware in order to send characters through the UART
  correctly. The result is that with the current machine model, VxWorks
  will boot and run in QEMU but it's unable to print any characters to
  the console serial port.

  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.

  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.

  I'm attaching the patch to this bug report. A copy can also be
  obtained from:

  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip

  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.

  My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
  2.11.0/2.11.11 built from source.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1753314/+subscriptions

[Qemu-devel] [Bug 1753314] Re: UART in sabrelite machine simulation doesn't work with VxWorks 7

[Peter Maydell]

That's fine; Andrey Smirnov has taken your patch as a basis for a more cleaned-up set of changes:
http://lists.nongnu.org/archive/html/qemu-devel/2018-03/msg04608.html
http://lists.nongnu.org/archive/html/qemu-devel/2018-03/msg04609.html
What we would like from you is a Signed-off-by: line to say that you're happy for us to do that, please. (If you have a chance to test that it works for you that would also be great.)

-- 
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https://bugs.launchpad.net/bugs/1753314

Title:
  UART in sabrelite machine simulation doesn't work with VxWorks 7

Status in QEMU:
  New

Bug description:
  The imx_serial.c driver currently implements only partial support for
  the i.MX6 UART hardware. (I understand it's a work in progress and
  that's fine.) dIn particular, it does not implement support for the
  Transmit Complete Interrupt Enable bit in the UCR4 register. The
  VxWorks 7 i.MX6 serial driver depends on the behavior of this bit in
  actual hardware in order to send characters through the UART
  correctly. The result is that with the current machine model, VxWorks
  will boot and run in QEMU but it's unable to print any characters to
  the console serial port.

  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.

  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.

  I'm attaching the patch to this bug report. A copy can also be
  obtained from:

  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip

  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.

  My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
  2.11.0/2.11.11 built from source.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1753314/+subscriptions

[Qemu-devel] [Bug 1753314] Re: UART in sabrelite machine simulation doesn't work with VxWorks 7

[Peter Maydell]

Now fixed in git master, should be in 2.12.


** Changed in: qemu
       Status: New => Fix Committed

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Title:
  UART in sabrelite machine simulation doesn't work with VxWorks 7

Status in QEMU:
  Fix Committed

Bug description:
  The imx_serial.c driver currently implements only partial support for
  the i.MX6 UART hardware. (I understand it's a work in progress and
  that's fine.) dIn particular, it does not implement support for the
  Transmit Complete Interrupt Enable bit in the UCR4 register. The
  VxWorks 7 i.MX6 serial driver depends on the behavior of this bit in
  actual hardware in order to send characters through the UART
  correctly. The result is that with the current machine model, VxWorks
  will boot and run in QEMU but it's unable to print any characters to
  the console serial port.

  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.

  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.

  I'm attaching the patch to this bug report. A copy can also be
  obtained from:

  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip

  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.

  My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
  2.11.0/2.11.11 built from source.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1753314/+subscriptions

[Qemu-devel] [Bug 1753314] Re: UART in sabrelite machine simulation doesn't work with VxWorks 7

[Thomas Huth]

** Changed in: qemu
       Status: Fix Committed => Fix Released

-- 
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https://bugs.launchpad.net/bugs/1753314

Title:
  UART in sabrelite machine simulation doesn't work with VxWorks 7

Status in QEMU:
  Fix Released

Bug description:
  The imx_serial.c driver currently implements only partial support for
  the i.MX6 UART hardware. (I understand it's a work in progress and
  that's fine.) dIn particular, it does not implement support for the
  Transmit Complete Interrupt Enable bit in the UCR4 register. The
  VxWorks 7 i.MX6 serial driver depends on the behavior of this bit in
  actual hardware in order to send characters through the UART
  correctly. The result is that with the current machine model, VxWorks
  will boot and run in QEMU but it's unable to print any characters to
  the console serial port.

  I have produced a small patch for the imx_serial.c module to make it
  nominally functional with VxWorks 7. It works well enough to allow the
  boot banner to appear and for the user to interact with the target
  shell.

  I'm not submitting this as a patch to the development list as I'm not
  fully certain it complies with the hardware spec and doesn't break any
  other functionality. I would prefer if the maintainer (or someone)
  reviewed it for any issues/refinements first.

  I'm attaching the patch to this bug report. A copy can also be
  obtained from:

  http://people.freebsd.org/~wpaul/qemu/imx_serial.zip

  This patch was generated against QEMU 2.11.0 but also works with QEMU
  2.11.1.

  My host environment is FreeBSD/amd64 11.1-RELEASE with QEMU
  2.11.0/2.11.11 built from source.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1753314/+subscriptions