[PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Valentine Barshak]

Currently find_legacy_serial_ports() can find no serial ports on the OPB.
Thus no legacy boot console can be initialized. Just the early udbg console
works, which is initialized with udbg_init_44x_as1() on the UART's physical
address specified in kernel config. This happens because we look for ns16750
and higher serial devices only and expect opb node to have a device type
property. This patch makes it look for ns16550 compatible devices and use
of_device_is_compatible() for opb instead of checking device type.
Lack of legacy serial ports found causes problems for KGDB over serial.

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
---
 arch/powerpc/kernel/legacy_serial.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff -pruN linux-2.6.orig/arch/powerpc/kernel/legacy_serial.c linux-2.6/arch/powerpc/kernel/legacy_serial.c
--- linux-2.6.orig/arch/powerpc/kernel/legacy_serial.c	2007-10-11 17:12:09.000000000 +0400
+++ linux-2.6/arch/powerpc/kernel/legacy_serial.c	2007-10-11 17:40:11.000000000 +0400
@@ -340,9 +340,9 @@ void __init find_legacy_serial_ports(voi
 	}
 
 	/* First fill our array with opb bus ports */
-	for (np = NULL; (np = of_find_compatible_node(np, "serial", "ns16750")) != NULL;) {
+	for (np = NULL; (np = of_find_compatible_node(np, "serial", "ns16550")) != NULL;) {
 		struct device_node *opb = of_get_parent(np);
-		if (opb && !strcmp(opb->type, "opb")) {
+		if (opb && of_device_is_compatible(opb, "ibm,opb")) {
 			index = add_legacy_soc_port(np, np);
 			if (index >= 0 && np == stdout)
 				legacy_serial_console = index;

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Arnd Bergmann]

On Thursday 11 October 2007, Valentine Barshak wrote:
> Currently find_legacy_serial_ports() can find no serial ports on the OPB.
> Thus no legacy boot console can be initialized. Just the early udbg console
> works, which is initialized with udbg_init_44x_as1() on the UART's physical
> address specified in kernel config. This happens because we look for ns16750
> and higher serial devices only and expect opb node to have a device type
> property. This patch makes it look for ns16550 compatible devices and use
> of_device_is_compatible() for opb instead of checking device type.
> Lack of legacy serial ports found causes problems for KGDB over serial.
> 
> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>

The patch would make sense if we were only dealing with flattened device
tree systems at this point. Unfortunately, IBM is shipping hardware that
encodes the serial port in exactly the way that find_legacy_serial_ports
is looking for (parent->type == "opb", compatible = "ns16750" "ns16550"
"ns16450" i8250").

Changing the search for ns16750 to ns16550 should be fine, but unnecessary
because AFAIK, all OPB serial imlpementations are actually ns16750 and
should have that in the device tree as well.

For the device type of the bus, please check for both compatible and
type, so that it still works on machines that are missing the compatible
property.

	Arnd <><

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Josh Boyer]

On Thu, 2007-10-11 at 17:50 +0200, Arnd Bergmann wrote:
> On Thursday 11 October 2007, Valentine Barshak wrote:
> > Currently find_legacy_serial_ports() can find no serial ports on the OPB.
> > Thus no legacy boot console can be initialized. Just the early udbg console
> > works, which is initialized with udbg_init_44x_as1() on the UART's physical
> > address specified in kernel config. This happens because we look for ns16750
> > and higher serial devices only and expect opb node to have a device type
> > property. This patch makes it look for ns16550 compatible devices and use
> > of_device_is_compatible() for opb instead of checking device type.
> > Lack of legacy serial ports found causes problems for KGDB over serial.
> > 
> > Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
> 
> The patch would make sense if we were only dealing with flattened device
> tree systems at this point. Unfortunately, IBM is shipping hardware that
> encodes the serial port in exactly the way that find_legacy_serial_ports
> is looking for (parent->type == "opb", compatible = "ns16750" "ns16550"
> "ns16450" i8250").
> 
> Changing the search for ns16750 to ns16550 should be fine, but unnecessary
> because AFAIK, all OPB serial imlpementations are actually ns16750 and
> should have that in the device tree as well.
> 
> For the device type of the bus, please check for both compatible and
> type, so that it still works on machines that are missing the compatible
> property.

Wait, no.  We already had this discussion months ago when David was
working on the original Ebony port.  It was declared that legacy_serial
is not how serial should be done on 4xx and the serial_of driver was
supposed to be used instead.

Have we changed our stance on that?  If not, then perhaps KGDB should be
fixed to work with serial_of.

josh

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Arnd Bergmann]

On Thursday 11 October 2007, Josh Boyer wrote:
> Wait, no. =A0We already had this discussion months ago when David was
> working on the original Ebony port. =A0It was declared that legacy_serial
> is not how serial should be done on 4xx and the serial_of driver was
> supposed to be used instead.
>=20
> Have we changed our stance on that? =A0If not, then perhaps KGDB should be
> fixed to work with serial_of.

I guess I'm fine with a patch that removes the OPB probing from
legacy_serial, but as long as it's there it should work on all
platforms.

Note that of_serial and legacy_serial are not exclusive, as of_serial
will simply take over all ports that have previously been registered
by the legacy code. Probing them early has the advantage that you
can see many printk messages earlier when the of_serial initialization
has not been called yet.

	Arnd <><

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Valentine Barshak]

Josh Boyer wrote:
> On Thu, 2007-10-11 at 17:50 +0200, Arnd Bergmann wrote:
>> On Thursday 11 October 2007, Valentine Barshak wrote:
>>> Currently find_legacy_serial_ports() can find no serial ports on the OPB.
>>> Thus no legacy boot console can be initialized. Just the early udbg console
>>> works, which is initialized with udbg_init_44x_as1() on the UART's physical
>>> address specified in kernel config. This happens because we look for ns16750
>>> and higher serial devices only and expect opb node to have a device type
>>> property. This patch makes it look for ns16550 compatible devices and use
>>> of_device_is_compatible() for opb instead of checking device type.
>>> Lack of legacy serial ports found causes problems for KGDB over serial.
>>>
>>> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
>> The patch would make sense if we were only dealing with flattened device
>> tree systems at this point. Unfortunately, IBM is shipping hardware that
>> encodes the serial port in exactly the way that find_legacy_serial_ports
>> is looking for (parent->type == "opb", compatible = "ns16750" "ns16550"
>> "ns16450" i8250").
>>
>> Changing the search for ns16750 to ns16550 should be fine, but unnecessary
>> because AFAIK, all OPB serial imlpementations are actually ns16750 and
>> should have that in the device tree as well.
>>
>> For the device type of the bus, please check for both compatible and
>> type, so that it still works on machines that are missing the compatible
>> property.
> 
> Wait, no.  We already had this discussion months ago when David was
> working on the original Ebony port.  It was declared that legacy_serial
> is not how serial should be done on 4xx and the serial_of driver was
> supposed to be used instead.
> 
> Have we changed our stance on that?  If not, then perhaps KGDB should be
> fixed to work with serial_of.

Actually I don't see any reason not to use legacy_serial stuff for early 
console. We could split the kernel configured very early debug output, 
which uses  PPC_EARLY_DEBUG_44x_PHYSLOW/PHYSHIGH (since it's really 
dangerous) and early console things by using legacy serial. We could use 
  early boot console without PPC_EARLY_DEBUG_44x.
Thanks,
Valentine.

> 
> josh
> 
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Josh Boyer]

On Thu, 2007-10-11 at 21:26 +0400, Valentine Barshak wrote:
> Josh Boyer wrote:
> > On Thu, 2007-10-11 at 17:50 +0200, Arnd Bergmann wrote:
> >> On Thursday 11 October 2007, Valentine Barshak wrote:
> >>> Currently find_legacy_serial_ports() can find no serial ports on the OPB.
> >>> Thus no legacy boot console can be initialized. Just the early udbg console
> >>> works, which is initialized with udbg_init_44x_as1() on the UART's physical
> >>> address specified in kernel config. This happens because we look for ns16750
> >>> and higher serial devices only and expect opb node to have a device type
> >>> property. This patch makes it look for ns16550 compatible devices and use
> >>> of_device_is_compatible() for opb instead of checking device type.
> >>> Lack of legacy serial ports found causes problems for KGDB over serial.
> >>>
> >>> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
> >> The patch would make sense if we were only dealing with flattened device
> >> tree systems at this point. Unfortunately, IBM is shipping hardware that
> >> encodes the serial port in exactly the way that find_legacy_serial_ports
> >> is looking for (parent->type == "opb", compatible = "ns16750" "ns16550"
> >> "ns16450" i8250").
> >>
> >> Changing the search for ns16750 to ns16550 should be fine, but unnecessary
> >> because AFAIK, all OPB serial imlpementations are actually ns16750 and
> >> should have that in the device tree as well.
> >>
> >> For the device type of the bus, please check for both compatible and
> >> type, so that it still works on machines that are missing the compatible
> >> property.
> > 
> > Wait, no.  We already had this discussion months ago when David was
> > working on the original Ebony port.  It was declared that legacy_serial
> > is not how serial should be done on 4xx and the serial_of driver was
> > supposed to be used instead.
> > 
> > Have we changed our stance on that?  If not, then perhaps KGDB should be
> > fixed to work with serial_of.
> 
> Actually I don't see any reason not to use legacy_serial stuff for early 
> console. We could split the kernel configured very early debug output, 
> which uses  PPC_EARLY_DEBUG_44x_PHYSLOW/PHYSHIGH (since it's really 
> dangerous) and early console things by using legacy serial. We could use 
>   early boot console without PPC_EARLY_DEBUG_44x.

That was exactly my thinking when this first came up.  I'd like to hear
David's opinion on it.

josh

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Valentine Barshak]

Arnd Bergmann wrote:
> On Thursday 11 October 2007, Valentine Barshak wrote:
>> Currently find_legacy_serial_ports() can find no serial ports on the OPB.
>> Thus no legacy boot console can be initialized. Just the early udbg console
>> works, which is initialized with udbg_init_44x_as1() on the UART's physical
>> address specified in kernel config. This happens because we look for ns16750
>> and higher serial devices only and expect opb node to have a device type
>> property. This patch makes it look for ns16550 compatible devices and use
>> of_device_is_compatible() for opb instead of checking device type.
>> Lack of legacy serial ports found causes problems for KGDB over serial.
>>
>> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
> 
> The patch would make sense if we were only dealing with flattened device
> tree systems at this point. Unfortunately, IBM is shipping hardware that
> encodes the serial port in exactly the way that find_legacy_serial_ports
> is looking for (parent->type == "opb", compatible = "ns16750" "ns16550"
> "ns16450" i8250").
> 
> Changing the search for ns16750 to ns16550 should be fine, but unnecessary
> because AFAIK, all OPB serial imlpementations are actually ns16750 and
> should have that in the device tree as well.

This is a bit odd. The docs say that uart chips on the ppc44x processors 
are registry-compatible to 16750, but have 16-byte FIFO's.
This is OK for legacy serial stuff (since it really needs the chip to be 
16550-compatible), but the 8250 driver expects 64-byte FIFO size for 16750.
I guess that's why 44x uart dts entries don't have 16750 compatible 
property.

> 
> For the device type of the bus, please check for both compatible and
> type, so that it still works on machines that are missing the compatible
> property.
> 
> 	Arnd <><

[PATCH] PowerPC: Add legacy serial support for OPB with flattened device tree.

[Valentine Barshak]

Currently find_legacy_serial_ports() can find no serial ports on the OPB
with flattened device. Thus no legacy boot console can be initialized.
Just the early udbg console works, which is initialized with udbg_init_44x_as1
on the UART's physical address specified in kernel config. This happens
because we look for ns16750 serial devices only and expect opb node to have
a device type property. This patch makes it look for ns16550-compatible
devices and use of_device_is_compatible() for opb in case device type is not
specified.

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
---
 arch/powerpc/kernel/legacy_serial.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff -pruN linux-2.6.orig/arch/powerpc/kernel/legacy_serial.c linux-2.6/arch/powerpc/kernel/legacy_serial.c
--- linux-2.6.orig/arch/powerpc/kernel/legacy_serial.c	2007-10-11 17:12:09.000000000 +0400
+++ linux-2.6/arch/powerpc/kernel/legacy_serial.c	2007-10-11 23:01:25.000000000 +0400
@@ -340,9 +340,10 @@ void __init find_legacy_serial_ports(voi
 	}
 
 	/* First fill our array with opb bus ports */
-	for (np = NULL; (np = of_find_compatible_node(np, "serial", "ns16750")) != NULL;) {
+	for (np = NULL; (np = of_find_compatible_node(np, "serial", "ns16550")) != NULL;) {
 		struct device_node *opb = of_get_parent(np);
-		if (opb && !strcmp(opb->type, "opb")) {
+		if (opb && (!strcmp(opb->type, "opb") ||
+			    of_device_is_compatible(opb, "ibm,opb"))) {
 			index = add_legacy_soc_port(np, np);
 			if (index >= 0 && np == stdout)
 				legacy_serial_console = index;

Re: [PATCH] PowerPC: Add legacy serial support for OPB with flattened device tree.

[Arnd Bergmann]

On Thursday 11 October 2007, Valentine Barshak wrote:
> Currently find_legacy_serial_ports() can find no serial ports on the OPB
> with flattened device. Thus no legacy boot console can be initialized.
> Just the early udbg console works, which is initialized with udbg_init_44x_as1
> on the UART's physical address specified in kernel config. This happens
> because we look for ns16750 serial devices only and expect opb node to have
> a device type property. This patch makes it look for ns16550-compatible
> devices and use of_device_is_compatible() for opb in case device type is not
> specified.
> 
> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>

Looks correct for QS21 now.

Acked-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[David Gibson]

On Thu, Oct 11, 2007 at 01:31:53PM -0500, Josh Boyer wrote:
> On Thu, 2007-10-11 at 21:26 +0400, Valentine Barshak wrote:
> > Josh Boyer wrote:
> > > On Thu, 2007-10-11 at 17:50 +0200, Arnd Bergmann wrote:
> > >> On Thursday 11 October 2007, Valentine Barshak wrote:
> > >>> Currently find_legacy_serial_ports() can find no serial ports on the OPB.
> > >>> Thus no legacy boot console can be initialized. Just the early udbg console
> > >>> works, which is initialized with udbg_init_44x_as1() on the UART's physical
> > >>> address specified in kernel config. This happens because we look for ns16750
> > >>> and higher serial devices only and expect opb node to have a device type
> > >>> property. This patch makes it look for ns16550 compatible devices and use
> > >>> of_device_is_compatible() for opb instead of checking device type.
> > >>> Lack of legacy serial ports found causes problems for KGDB over serial.
> > >>>
> > >>> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
> > >> The patch would make sense if we were only dealing with flattened device
> > >> tree systems at this point. Unfortunately, IBM is shipping hardware that
> > >> encodes the serial port in exactly the way that find_legacy_serial_ports
> > >> is looking for (parent->type == "opb", compatible = "ns16750" "ns16550"
> > >> "ns16450" i8250").
> > >>
> > >> Changing the search for ns16750 to ns16550 should be fine, but unnecessary
> > >> because AFAIK, all OPB serial imlpementations are actually ns16750 and
> > >> should have that in the device tree as well.
> > >>
> > >> For the device type of the bus, please check for both compatible and
> > >> type, so that it still works on machines that are missing the compatible
> > >> property.
> > > 
> > > Wait, no.  We already had this discussion months ago when David was
> > > working on the original Ebony port.  It was declared that legacy_serial
> > > is not how serial should be done on 4xx and the serial_of driver was
> > > supposed to be used instead.
> > > 
> > > Have we changed our stance on that?  If not, then perhaps KGDB should be
> > > fixed to work with serial_of.
> > 
> > Actually I don't see any reason not to use legacy_serial stuff for early 
> > console. We could split the kernel configured very early debug output, 
> > which uses  PPC_EARLY_DEBUG_44x_PHYSLOW/PHYSHIGH (since it's really 
> > dangerous) and early console things by using legacy serial. We could use 
> >   early boot console without PPC_EARLY_DEBUG_44x.
> 
> That was exactly my thinking when this first came up.  I'd like to hear
> David's opinion on it.

Yeah, I think I misinterpreted BenH way back when.  This looks ok, and
means serial will be initialized earlier than of_serial, which would
be nice.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

Re: [PATCH] PowerPC: Fix find_legacy_serial_ports on OPB.

[Josh Boyer]

On Fri, 2007-10-12 at 12:31 +1000, David Gibson wrote:
> On Thu, Oct 11, 2007 at 01:31:53PM -0500, Josh Boyer wrote:
> > On Thu, 2007-10-11 at 21:26 +0400, Valentine Barshak wrote:
> > > Josh Boyer wrote:
> > > > On Thu, 2007-10-11 at 17:50 +0200, Arnd Bergmann wrote:
> > > >> On Thursday 11 October 2007, Valentine Barshak wrote:
> > > >>> Currently find_legacy_serial_ports() can find no serial ports on the OPB.
> > > >>> Thus no legacy boot console can be initialized. Just the early udbg console
> > > >>> works, which is initialized with udbg_init_44x_as1() on the UART's physical
> > > >>> address specified in kernel config. This happens because we look for ns16750
> > > >>> and higher serial devices only and expect opb node to have a device type
> > > >>> property. This patch makes it look for ns16550 compatible devices and use
> > > >>> of_device_is_compatible() for opb instead of checking device type.
> > > >>> Lack of legacy serial ports found causes problems for KGDB over serial.
> > > >>>
> > > >>> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
> > > >> The patch would make sense if we were only dealing with flattened device
> > > >> tree systems at this point. Unfortunately, IBM is shipping hardware that
> > > >> encodes the serial port in exactly the way that find_legacy_serial_ports
> > > >> is looking for (parent->type == "opb", compatible = "ns16750" "ns16550"
> > > >> "ns16450" i8250").
> > > >>
> > > >> Changing the search for ns16750 to ns16550 should be fine, but unnecessary
> > > >> because AFAIK, all OPB serial imlpementations are actually ns16750 and
> > > >> should have that in the device tree as well.
> > > >>
> > > >> For the device type of the bus, please check for both compatible and
> > > >> type, so that it still works on machines that are missing the compatible
> > > >> property.
> > > > 
> > > > Wait, no.  We already had this discussion months ago when David was
> > > > working on the original Ebony port.  It was declared that legacy_serial
> > > > is not how serial should be done on 4xx and the serial_of driver was
> > > > supposed to be used instead.
> > > > 
> > > > Have we changed our stance on that?  If not, then perhaps KGDB should be
> > > > fixed to work with serial_of.
> > > 
> > > Actually I don't see any reason not to use legacy_serial stuff for early 
> > > console. We could split the kernel configured very early debug output, 
> > > which uses  PPC_EARLY_DEBUG_44x_PHYSLOW/PHYSHIGH (since it's really 
> > > dangerous) and early console things by using legacy serial. We could use 
> > >   early boot console without PPC_EARLY_DEBUG_44x.
> > 
> > That was exactly my thinking when this first came up.  I'd like to hear
> > David's opinion on it.
> 
> Yeah, I think I misinterpreted BenH way back when.  This looks ok, and
> means serial will be initialized earlier than of_serial, which would
> be nice.

Great.  It seems Paul pulled it into his tree already as well, which
suits me just fine.

josh