<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/drivers/tty/serial, branch v3.8.4</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>Fix 4 port and add support for 8 port 'Unknown' PCI serial port cards</title>
<updated>2013-03-20T20:10:54+00:00</updated>
<author>
<name>Scott Ashcroft</name>
<email>scott.ashcroft@talk21.com</email>
</author>
<published>2013-03-03T21:35:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=f2ebfa449f40a0dc0ff35ab35a35744c4d249b82'/>
<id>f2ebfa449f40a0dc0ff35ab35a35744c4d249b82</id>
<content type='text'>
commit d13402a4a944e72612a9ec5c9190e35717c02a9d upstream.

I've managed to find an 8 port version of the card 4 port card which was discussed here:

http://marc.info/?l=linux-serial&amp;m=120760744205314&amp;w=2

Looking back at that thread there were two issues in the original patch.

1) The I/O ports for the UARTs are within BAR2 not BAR0. This can been seen in the original post.
2) A serial quirk isn't needed as these cards have no memory in BAR0 which makes pci_plx9050_init just return.

This patch fixes the 4 port support to use BAR2, removes the bogus quirk and adds support for the 8 port card.

$ lspci -vvv -n -s 00:08.0
00:08.0 0780: 10b5:9050 (rev 01)
	Subsystem: 10b5:1588
	Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium &gt;TAbort- &lt;TAbort- &lt;MAbort- &gt;SERR- &lt;PERR- INTx-
	Interrupt: pin A routed to IRQ 17
	Region 1: I/O ports at ff00 [size=128]
	Region 2: I/O ports at fe00 [size=64]
	Region 3: I/O ports at fd00 [size=8]
	Capabilities: &lt;access denied&gt;
	Kernel driver in use: serial

$ dmesg | grep 0000:00:08.0:
[    0.083320] pci 0000:00:08.0: [10b5:9050] type 0 class 0x000780
[    0.083355] pci 0000:00:08.0: reg 14: [io  0xff00-0xff7f]
[    0.083369] pci 0000:00:08.0: reg 18: [io  0xfe00-0xfe3f]
[    0.083382] pci 0000:00:08.0: reg 1c: [io  0xfd00-0xfd07]
[    0.083460] pci 0000:00:08.0: PME# supported from D0 D3hot
[    1.212867] 0000:00:08.0: ttyS4 at I/O 0xfe00 (irq = 17) is a 16550A
[    1.233073] 0000:00:08.0: ttyS5 at I/O 0xfe08 (irq = 17) is a 16550A
[    1.253270] 0000:00:08.0: ttyS6 at I/O 0xfe10 (irq = 17) is a 16550A
[    1.273468] 0000:00:08.0: ttyS7 at I/O 0xfe18 (irq = 17) is a 16550A
[    1.293666] 0000:00:08.0: ttyS8 at I/O 0xfe20 (irq = 17) is a 16550A
[    1.313863] 0000:00:08.0: ttyS9 at I/O 0xfe28 (irq = 17) is a 16550A
[    1.334061] 0000:00:08.0: ttyS10 at I/O 0xfe30 (irq = 17) is a 16550A
[    1.354258] 0000:00:08.0: ttyS11 at I/O 0xfe38 (irq = 17) is a 16550A

Signed-off-by: Scott Ashcroft &lt;scott.ashcroft@talk21.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit d13402a4a944e72612a9ec5c9190e35717c02a9d upstream.

I've managed to find an 8 port version of the card 4 port card which was discussed here:

http://marc.info/?l=linux-serial&amp;m=120760744205314&amp;w=2

Looking back at that thread there were two issues in the original patch.

1) The I/O ports for the UARTs are within BAR2 not BAR0. This can been seen in the original post.
2) A serial quirk isn't needed as these cards have no memory in BAR0 which makes pci_plx9050_init just return.

This patch fixes the 4 port support to use BAR2, removes the bogus quirk and adds support for the 8 port card.

$ lspci -vvv -n -s 00:08.0
00:08.0 0780: 10b5:9050 (rev 01)
	Subsystem: 10b5:1588
	Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium &gt;TAbort- &lt;TAbort- &lt;MAbort- &gt;SERR- &lt;PERR- INTx-
	Interrupt: pin A routed to IRQ 17
	Region 1: I/O ports at ff00 [size=128]
	Region 2: I/O ports at fe00 [size=64]
	Region 3: I/O ports at fd00 [size=8]
	Capabilities: &lt;access denied&gt;
	Kernel driver in use: serial

$ dmesg | grep 0000:00:08.0:
[    0.083320] pci 0000:00:08.0: [10b5:9050] type 0 class 0x000780
[    0.083355] pci 0000:00:08.0: reg 14: [io  0xff00-0xff7f]
[    0.083369] pci 0000:00:08.0: reg 18: [io  0xfe00-0xfe3f]
[    0.083382] pci 0000:00:08.0: reg 1c: [io  0xfd00-0xfd07]
[    0.083460] pci 0000:00:08.0: PME# supported from D0 D3hot
[    1.212867] 0000:00:08.0: ttyS4 at I/O 0xfe00 (irq = 17) is a 16550A
[    1.233073] 0000:00:08.0: ttyS5 at I/O 0xfe08 (irq = 17) is a 16550A
[    1.253270] 0000:00:08.0: ttyS6 at I/O 0xfe10 (irq = 17) is a 16550A
[    1.273468] 0000:00:08.0: ttyS7 at I/O 0xfe18 (irq = 17) is a 16550A
[    1.293666] 0000:00:08.0: ttyS8 at I/O 0xfe20 (irq = 17) is a 16550A
[    1.313863] 0000:00:08.0: ttyS9 at I/O 0xfe28 (irq = 17) is a 16550A
[    1.334061] 0000:00:08.0: ttyS10 at I/O 0xfe30 (irq = 17) is a 16550A
[    1.354258] 0000:00:08.0: ttyS11 at I/O 0xfe38 (irq = 17) is a 16550A

Signed-off-by: Scott Ashcroft &lt;scott.ashcroft@talk21.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>tty/serial: Add support for Altera serial port</title>
<updated>2013-03-20T20:10:54+00:00</updated>
<author>
<name>Ley Foon Tan</name>
<email>lftan@altera.com</email>
</author>
<published>2013-03-07T02:28:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=ec99e285dbd0dfc65495b459b57b35e1ce5dc55c'/>
<id>ec99e285dbd0dfc65495b459b57b35e1ce5dc55c</id>
<content type='text'>
commit e06c93cacb82dd147266fd1bdb2d0a0bd45ff2c1 upstream.

Add support for Altera 8250/16550 compatible serial port.

Signed-off-by: Ley Foon Tan &lt;lftan@altera.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit e06c93cacb82dd147266fd1bdb2d0a0bd45ff2c1 upstream.

Add support for Altera 8250/16550 compatible serial port.

Signed-off-by: Ley Foon Tan &lt;lftan@altera.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>tty: serial: fix typo "SERIAL_S3C2412"</title>
<updated>2013-03-20T20:10:54+00:00</updated>
<author>
<name>Paul Bolle</name>
<email>pebolle@tiscali.nl</email>
</author>
<published>2013-03-12T09:10:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=53b90339a62ec1d726130a4ad273d826ebefc04d'/>
<id>53b90339a62ec1d726130a4ad273d826ebefc04d</id>
<content type='text'>
commit c51d41a1dd8f23a06a4ed651ebb9617de7f59368 upstream.

The Kconfig symbol SERIAL_S3C2412 got removed in commit
da121506eb03ee5daea55404709110b798bd61d9 ("serial: samsung: merge
probe() function from all SoC specific extensions"). But it also added a
last reference to that symbol. The commit and the tree make clear that
CPU_S3C2412 should have been used instead.

Signed-off-by: Paul Bolle &lt;pebolle@tiscali.nl&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit c51d41a1dd8f23a06a4ed651ebb9617de7f59368 upstream.

The Kconfig symbol SERIAL_S3C2412 got removed in commit
da121506eb03ee5daea55404709110b798bd61d9 ("serial: samsung: merge
probe() function from all SoC specific extensions"). But it also added a
last reference to that symbol. The commit and the tree make clear that
CPU_S3C2412 should have been used instead.

Signed-off-by: Paul Bolle &lt;pebolle@tiscali.nl&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>tty: serial: fix typo "ARCH_S5P6450"</title>
<updated>2013-03-20T20:10:54+00:00</updated>
<author>
<name>Paul Bolle</name>
<email>pebolle@tiscali.nl</email>
</author>
<published>2013-03-09T22:16:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=ce05554900c8b8f9c68988c5823428f8730ed445'/>
<id>ce05554900c8b8f9c68988c5823428f8730ed445</id>
<content type='text'>
commit 827aa0d36d486f359808c8fb931cf7a71011a09d upstream.

This could have been either ARCH_S5P64X0 or CPU_S5P6450. Looking at
commit 2555e663b367b8d555e76023f4de3f6338c28d6c ("ARM: S5P64X0: Add UART
serial support for S5P6450") - which added this typo - makes clear this
should be CPU_S5P6450.

Signed-off-by: Paul Bolle &lt;pebolle@tiscali.nl&gt;
Acked-by: Kukjin Kim &lt;kgene.kim@samsung.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 827aa0d36d486f359808c8fb931cf7a71011a09d upstream.

This could have been either ARCH_S5P64X0 or CPU_S5P6450. Looking at
commit 2555e663b367b8d555e76023f4de3f6338c28d6c ("ARM: S5P64X0: Add UART
serial support for S5P6450") - which added this typo - makes clear this
should be CPU_S5P6450.

Signed-off-by: Paul Bolle &lt;pebolle@tiscali.nl&gt;
Acked-by: Kukjin Kim &lt;kgene.kim@samsung.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>serial: 8250_pci: add support for another kind of NetMos Technology PCI 9835 Multi-I/O Controller</title>
<updated>2013-03-20T20:10:53+00:00</updated>
<author>
<name>Wang YanQing</name>
<email>udknight@gmail.com</email>
</author>
<published>2013-03-01T03:47:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=9858f47888317bf404d73715cfe8746df95ab351'/>
<id>9858f47888317bf404d73715cfe8746df95ab351</id>
<content type='text'>
commit 8d2f8cd424ca0b99001f3ff4f5db87c4e525f366 upstream.

01:08.0 Communication controller: NetMos Technology PCI 9835 Multi-I/O Controller (rev 01)
	Subsystem: Device [1000:0012]
	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium &gt;TAbort- &lt;TAbort- &lt;MAbort- &gt;SERR- &lt;PERR- INTx-
	Interrupt: pin A routed to IRQ 20
	Region 0: I/O ports at e050 [size=8]
	Region 1: I/O ports at e040 [size=8]
	Region 2: I/O ports at e030 [size=8]
	Region 3: I/O ports at e020 [size=8]
	Region 4: I/O ports at e010 [size=8]
	Region 5: I/O ports at e000 [size=16]

Signed-off-by: Wang YanQing &lt;udknight@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 8d2f8cd424ca0b99001f3ff4f5db87c4e525f366 upstream.

01:08.0 Communication controller: NetMos Technology PCI 9835 Multi-I/O Controller (rev 01)
	Subsystem: Device [1000:0012]
	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium &gt;TAbort- &lt;TAbort- &lt;MAbort- &gt;SERR- &lt;PERR- INTx-
	Interrupt: pin A routed to IRQ 20
	Region 0: I/O ports at e050 [size=8]
	Region 1: I/O ports at e040 [size=8]
	Region 2: I/O ports at e030 [size=8]
	Region 3: I/O ports at e020 [size=8]
	Region 4: I/O ports at e010 [size=8]
	Region 5: I/O ports at e000 [size=16]

Signed-off-by: Wang YanQing &lt;udknight@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>serial: 8250: Keep 8250.&lt;xxxx&gt; module options functional after driver rename</title>
<updated>2013-03-20T20:10:53+00:00</updated>
<author>
<name>Josh Boyer</name>
<email>jwboyer@redhat.com</email>
</author>
<published>2013-03-10T14:33:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=afe509cd07fb6af0356b7c49a96fc4bb1dbf5210'/>
<id>afe509cd07fb6af0356b7c49a96fc4bb1dbf5210</id>
<content type='text'>
commit f2b8dfd9e480c3db3bad0c25c590a5d11b31f4ef upstream.

With commit 835d844d1 (8250_pnp: do pnp probe before legacy probe), the
8250 driver was renamed to 8250_core.  This means any existing usage of
the 8259.&lt;xxxx&gt; module parameters or as a kernel command line switch is
now broken, as the 8250_core driver doesn't parse options belonging to
something called "8250".

To solve this, we redefine the module options in a dummy function using
a redefined MODULE_PARAM_PREFX when built into the kernel.  In the case
where we're building as a module, we provide an alias to the old 8250
name.  The dummy function prevents compiler errors due to global variable
redefinitions that happen as part of the module_param_ macro expansions.

Signed-off-by: Josh Boyer &lt;jwboyer@redhat.com&gt;
Acked-by: Jiri Slaby &lt;jslaby@suse.cz&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit f2b8dfd9e480c3db3bad0c25c590a5d11b31f4ef upstream.

With commit 835d844d1 (8250_pnp: do pnp probe before legacy probe), the
8250 driver was renamed to 8250_core.  This means any existing usage of
the 8259.&lt;xxxx&gt; module parameters or as a kernel command line switch is
now broken, as the 8250_core driver doesn't parse options belonging to
something called "8250".

To solve this, we redefine the module options in a dummy function using
a redefined MODULE_PARAM_PREFX when built into the kernel.  In the case
where we're building as a module, we provide an alias to the old 8250
name.  The dummy function prevents compiler errors due to global variable
redefinitions that happen as part of the module_param_ macro expansions.

Signed-off-by: Josh Boyer &lt;jwboyer@redhat.com&gt;
Acked-by: Jiri Slaby &lt;jslaby@suse.cz&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>tty/8250_pnp: serial port detection regression since v3.7</title>
<updated>2013-03-20T20:10:53+00:00</updated>
<author>
<name>Sean Young</name>
<email>sean@mess.org</email>
</author>
<published>2013-02-22T16:27:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=eec98f82c63730d039e4a87f623cfcf5ac612683'/>
<id>eec98f82c63730d039e4a87f623cfcf5ac612683</id>
<content type='text'>
commit 77e372a3d82e5e4878ce1962207edd766773cc76 upstream.

The InsydeH2O BIOS (version dated 09/12/2011) has the following in
its pnp resouces for its serial ports:

$ cat /sys/bus/pnp/devices/00:0b/resources
state = active
io disabled
irq disabled

We do not check if the resources are disabled, and create a bogus
ttyS* device. Since commit 835d844d1a28e (8250_pnp: do pnp probe
before legacy probe) we get a bogus ttyS0, which prevents the legacy
probe from detecting it.

Note, the BIOS can also be upgraded, fixing this problem, but for people
who can't do that, this fix is needed.

Reported-by: Vincent Deffontaines &lt;vincent@gryzor.com&gt;
Tested-by: Vincent Deffontaines &lt;vincent@gryzor.com&gt;
Signed-off-by: Sean Young &lt;sean@mess.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 77e372a3d82e5e4878ce1962207edd766773cc76 upstream.

The InsydeH2O BIOS (version dated 09/12/2011) has the following in
its pnp resouces for its serial ports:

$ cat /sys/bus/pnp/devices/00:0b/resources
state = active
io disabled
irq disabled

We do not check if the resources are disabled, and create a bogus
ttyS* device. Since commit 835d844d1a28e (8250_pnp: do pnp probe
before legacy probe) we get a bogus ttyS0, which prevents the legacy
probe from detecting it.

Note, the BIOS can also be upgraded, fixing this problem, but for people
who can't do that, this fix is needed.

Reported-by: Vincent Deffontaines &lt;vincent@gryzor.com&gt;
Tested-by: Vincent Deffontaines &lt;vincent@gryzor.com&gt;
Signed-off-by: Sean Young &lt;sean@mess.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>serial: imx: Fix recursive locking bug</title>
<updated>2013-02-28T13:38:29+00:00</updated>
<author>
<name>Thomas Gleixner</name>
<email>tglx@linutronix.de</email>
</author>
<published>2013-02-14T20:01:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e93a85ac6120ec0b3b53add0a5409f84aad135d8'/>
<id>e93a85ac6120ec0b3b53add0a5409f84aad135d8</id>
<content type='text'>
commit 677fe555cbfb188af58cce105f4dae9505e58c31 upstream.

commit 9ec1882df2 (tty: serial: imx: console write routing is unsafe
on SMP) introduced a recursive locking bug in imx_console_write().

The callchain is:

imx_rxint()
  spin_lock_irqsave(&amp;sport-&gt;port.lock,flags);
  ...
  uart_handle_sysrq_char();
    sysrq_function();
      printk();
        imx_console_write();
          spin_lock_irqsave(&amp;sport-&gt;port.lock,flags); &lt;--- DEAD

The bad news is that the kernel debugging facilities can dectect the
problem, but the printks never surface on the serial console for
obvious reasons.

There is a similar issue with oops_in_progress. If the kernel crashes
we really don't want to be stuck on the lock and unable to tell what
happened.

In general most UP originated drivers miss these checks and nobody
ever notices because CONFIG_PROVE_LOCKING seems to be still ignored by
a large number of developers.

The solution is to avoid locking in the sysrq case and trylock in the
oops_in_progress case.

This scheme is used in other drivers as well and it would be nice if
we could move this to a common place, so the usual copy/paste/modify
bugs can be avoided.

Now there is another issue with this scheme:

CPU0 	    	     	 CPU1
printk()
			 rxint()
			   sysrq_detection() -&gt; sets port-&gt;sysrq
			 return from interrupt
  console_write()
     if (port-&gt;sysrq)
     	avoid locking

port-&gt;sysrq is reset with the next receive character. So as long as
the port-&gt;sysrq is not reset and this can take an endless amount of
time if after the break no futher receive character follows, all
console writes happen unlocked.

While the current writer is protected against other console writers by
the console sem, it's unprotected against open/close or other
operations which fiddle with the port. That's what the above mentioned
commit tried to solve.

That's an issue in all drivers which use that scheme and unfortunately
there is no easy workaround. The only solution is to have a separate
indicator port-&gt;sysrq_cpu. uart_handle_sysrq_char() then sets it to
smp_processor_id() before calling into handle_sysrq() and resets it to
-1 after that. Then change the locking check to:

     if (port-&gt;sysrq_cpu == smp_processor_id())
     	 locked = 0;
     else if (oops_in_progress)
         locked = spin_trylock_irqsave(port-&gt;lock, flags);
     else
  	 spin_lock_irqsave(port-&gt;lock, flags);

That would force all other cpus into the spin_lock path. Problem
solved, but that's way beyond the scope of this fix and really wants
to be implemented in a common function which calls the uart specific
write function to avoid another gazillion of hard to debug
copy/paste/modify bugs.

Reported-and-tested-by: Tim Sander &lt;tim@krieglstein.org&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 677fe555cbfb188af58cce105f4dae9505e58c31 upstream.

commit 9ec1882df2 (tty: serial: imx: console write routing is unsafe
on SMP) introduced a recursive locking bug in imx_console_write().

The callchain is:

imx_rxint()
  spin_lock_irqsave(&amp;sport-&gt;port.lock,flags);
  ...
  uart_handle_sysrq_char();
    sysrq_function();
      printk();
        imx_console_write();
          spin_lock_irqsave(&amp;sport-&gt;port.lock,flags); &lt;--- DEAD

The bad news is that the kernel debugging facilities can dectect the
problem, but the printks never surface on the serial console for
obvious reasons.

There is a similar issue with oops_in_progress. If the kernel crashes
we really don't want to be stuck on the lock and unable to tell what
happened.

In general most UP originated drivers miss these checks and nobody
ever notices because CONFIG_PROVE_LOCKING seems to be still ignored by
a large number of developers.

The solution is to avoid locking in the sysrq case and trylock in the
oops_in_progress case.

This scheme is used in other drivers as well and it would be nice if
we could move this to a common place, so the usual copy/paste/modify
bugs can be avoided.

Now there is another issue with this scheme:

CPU0 	    	     	 CPU1
printk()
			 rxint()
			   sysrq_detection() -&gt; sets port-&gt;sysrq
			 return from interrupt
  console_write()
     if (port-&gt;sysrq)
     	avoid locking

port-&gt;sysrq is reset with the next receive character. So as long as
the port-&gt;sysrq is not reset and this can take an endless amount of
time if after the break no futher receive character follows, all
console writes happen unlocked.

While the current writer is protected against other console writers by
the console sem, it's unprotected against open/close or other
operations which fiddle with the port. That's what the above mentioned
commit tried to solve.

That's an issue in all drivers which use that scheme and unfortunately
there is no easy workaround. The only solution is to have a separate
indicator port-&gt;sysrq_cpu. uart_handle_sysrq_char() then sets it to
smp_processor_id() before calling into handle_sysrq() and resets it to
-1 after that. Then change the locking check to:

     if (port-&gt;sysrq_cpu == smp_processor_id())
     	 locked = 0;
     else if (oops_in_progress)
         locked = spin_trylock_irqsave(port-&gt;lock, flags);
     else
  	 spin_lock_irqsave(port-&gt;lock, flags);

That would force all other cpus into the spin_lock path. Problem
solved, but that's way beyond the scope of this fix and really wants
to be implemented in a common function which calls the uart specific
write function to avoid another gazillion of hard to debug
copy/paste/modify bugs.

Reported-and-tested-by: Tim Sander &lt;tim@krieglstein.org&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>8250/16?50: Add support for Broadcom TruManage redirected serial port</title>
<updated>2013-01-17T22:02:55+00:00</updated>
<author>
<name>Stephen Hurd</name>
<email>shurd@broadcom.com</email>
</author>
<published>2013-01-17T22:14:53+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=ebebd49a8eab5e9aa1b1f8f1614ccc3c2120f886'/>
<id>ebebd49a8eab5e9aa1b1f8f1614ccc3c2120f886</id>
<content type='text'>
Add support for the UART device present in Broadcom TruManage capable
NetXtreme chips (ie: 5761m 5762, and 5725).

This implementation has a hidden transmit FIFO, so running in single-byte
interrupt mode results in too many interrupts.  The UART_CAP_HFIFO
capability was added to track this.  It continues to reload the THR as long
as the THRE and TSRE bits are set in the LSR up to a specified limit (1024
is used here).

Signed-off-by: Stephen Hurd &lt;shurd@broadcom.com&gt;
Signed-off-by: Michael Chan &lt;mchan@broadcom.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add support for the UART device present in Broadcom TruManage capable
NetXtreme chips (ie: 5761m 5762, and 5725).

This implementation has a hidden transmit FIFO, so running in single-byte
interrupt mode results in too many interrupts.  The UART_CAP_HFIFO
capability was added to track this.  It continues to reload the THR as long
as the THRE and TSRE bits are set in the LSR up to a specified limit (1024
is used here).

Signed-off-by: Stephen Hurd &lt;shurd@broadcom.com&gt;
Signed-off-by: Michael Chan &lt;mchan@broadcom.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>serial:ifx6x60:Keep word size accordance with SPI controller</title>
<updated>2013-01-16T05:35:04+00:00</updated>
<author>
<name>channing</name>
<email>chao.bi@intel.com</email>
</author>
<published>2013-01-16T05:14:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=5dd070d21e2cb34b4162d564d73cca3591f94389'/>
<id>5dd070d21e2cb34b4162d564d73cca3591f94389</id>
<content type='text'>
As protocol driver, IFX SPI driver initiate to setup SPI master with default
SPI word size as 16 bit/word, however, SPI master may not adopt this default
value due to SPI controller's capability, it might choose an available value by
itself and set it to spi_device.bits_per_word. In order to keep align with
Controller, IFX driver should make use of this value during SPI transfer,
but the default one.

Signed-off-by: Chen Jun &lt;jun.d.chen@intel.com&gt;
Signed-off-by: channing &lt;chao.bi@intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
As protocol driver, IFX SPI driver initiate to setup SPI master with default
SPI word size as 16 bit/word, however, SPI master may not adopt this default
value due to SPI controller's capability, it might choose an available value by
itself and set it to spi_device.bits_per_word. In order to keep align with
Controller, IFX driver should make use of this value during SPI transfer,
but the default one.

Signed-off-by: Chen Jun &lt;jun.d.chen@intel.com&gt;
Signed-off-by: channing &lt;chao.bi@intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
