[PATCH 0/3] s/FOOTBRIDGE/ARCH_FOOTBRIDGE/

[PATCH 0/3] s/FOOTBRIDGE/ARCH_FOOTBRIDGE/

[Uwe Kleine-König]

Hello Russell,

I'm not sure that FOOTBRIDGE and ARCH_FOOTBRIDGE are semantically
identical; if not, feel free to nack this series.

Best regards
Uwe

Uwe Kleine-König (3):
  serial: DC21285: depend on ARCH_FOOTBRIDGE instead of FOOTBRIDGE
  watchdog: get rid of FOOTBRIDGE in dependencies
  ARM: drop Kconfig symbol FOOTBRIDGE

 arch/arm/Kconfig                 |  1 -
 arch/arm/Kconfig.debug           | 14 +++++++-------
 arch/arm/mach-footbridge/Kconfig |  4 ----
 drivers/tty/serial/Kconfig       |  2 +-
 drivers/watchdog/Kconfig         |  4 ++--
 5 files changed, 10 insertions(+), 15 deletions(-)

-- 
2.0.0

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[PATCH 1/3] serial: DC21285: depend on ARCH_FOOTBRIDGE instead of FOOTBRIDGE

[Uwe Kleine-König]

The Kconfig symbol FOOTBRIDGE is only defined if ARCH_FOOTBRIDGE is
enabled and the latter unconditionally selects the former. So they are
either both selected or none and so they are equivalent. To allow
removing FOOTBRIDGE switch the dependency of SERIAL_21285 to
ARCH_FOOTBRIDGE.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-serial@vger.kernel.org
---
 drivers/tty/serial/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index fb57159bad3a..570ca2ff55d1 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -380,7 +380,7 @@ config SERIAL_ZS_CONSOLE
 
 config SERIAL_21285
 	tristate "DC21285 serial port support"
-	depends on FOOTBRIDGE
+	depends on ARCH_FOOTBRIDGE
 	select SERIAL_CORE
 	help
 	  If you have a machine based on a 21285 (Footbridge) StrongARM(R)/
-- 
2.0.0

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Re: [PATCH 0/3] s/FOOTBRIDGE/ARCH_FOOTBRIDGE/

[Russell King - ARM Linux]

On Tue, Jul 01, 2014 at 10:37:03PM +0200, Uwe Kleine-König wrote:
> Hello Russell,
> 
> I'm not sure that FOOTBRIDGE and ARCH_FOOTBRIDGE are semantically
> identical; if not, feel free to nack this series.

CONFIG_FOOTBRIDGE means that we have a DC21285 in the system.  We
used to have ARCH_FOOTBRIDGE and ARCH_CO285 which both selected
CONFIG_FOOTBRIDGE.

ARCH_FOOTBRIDGE was for either host or addin mode using a PAGE_OFFSET
of 0xc0000000.  ARCH_CO285 had a PAGE_OFFSET of 0x80000000 as they
wanted to be able to map almost all of PCI memory space.

So think of CONFIG_FOOTBRIDGE as meaning that we have the physical
device, and CONFIG_ARCH_FOOTBRIDGE meaning that we want to support
boards with the device on.

So, it may make sense to rename CONFIG_FOOTBRIDGE to CONFIG_DC21285
if that makes the configuration symbol intention clearer.

This is why I prefer even hidden symbols to have a help text - having
the help text explains why they exist...

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Re: [PATCH 0/3] s/FOOTBRIDGE/ARCH_FOOTBRIDGE/

[Uwe Kleine-König]

Hello Russell,

On Tue, Jul 01, 2014 at 11:14:28PM +0100, Russell King - ARM Linux wrote:
> On Tue, Jul 01, 2014 at 10:37:03PM +0200, Uwe Kleine-König wrote:
> > I'm not sure that FOOTBRIDGE and ARCH_FOOTBRIDGE are semantically
> > identical; if not, feel free to nack this series.
> 
> CONFIG_FOOTBRIDGE means that we have a DC21285 in the system.  We
> used to have ARCH_FOOTBRIDGE and ARCH_CO285 which both selected
> CONFIG_FOOTBRIDGE.
> 
> ARCH_FOOTBRIDGE was for either host or addin mode using a PAGE_OFFSET
> of 0xc0000000.  ARCH_CO285 had a PAGE_OFFSET of 0x80000000 as they
> wanted to be able to map almost all of PCI memory space.
> 
> So think of CONFIG_FOOTBRIDGE as meaning that we have the physical
> device, and CONFIG_ARCH_FOOTBRIDGE meaning that we want to support
> boards with the device on.
I expected something like that. Is it possible to "have" the device on a
cpu != StrongARM? If so I wonder why ARCH_FOOTBRIDGE is a "ARM system
type". And if not, wouldn't it be possible and better to have all
platforms which select CPU_SA110 (ARCH_EBSA110, ARCH_FOOTBRIDGE; what
about RPC?) in a single mach dir and make FOOTBRIDGE an option there?

It's hard to find information on the net about these chips, even
http://developer.intel.com/design/strong/sa110.htm only talks about x86
stuff only, so please excuse my unknowingness.
 
> So, it may make sense to rename CONFIG_FOOTBRIDGE to CONFIG_DC21285
> if that makes the configuration symbol intention clearer.
Maybe even better CONFIG_HAS_DC21285?

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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Re: [PATCH 0/3] s/FOOTBRIDGE/ARCH_FOOTBRIDGE/

[Russell King - ARM Linux]

On Wed, Jul 02, 2014 at 09:13:12AM +0200, Uwe Kleine-König wrote:
> I expected something like that. Is it possible to "have" the device on a
> cpu != StrongARM? If so I wonder why ARCH_FOOTBRIDGE is a "ARM system
> type". And if not, wouldn't it be possible and better to have all
> platforms which select CPU_SA110 (ARCH_EBSA110, ARCH_FOOTBRIDGE; what
> about RPC?) in a single mach dir and make FOOTBRIDGE an option there?
> 
> It's hard to find information on the net about these chips, even
> http://developer.intel.com/design/strong/sa110.htm only talks about x86
> stuff only, so please excuse my unknowingness.

The Footbridge is a companion device to the StrongARM - the two are
designed to work together.  It probably is possible that the Footbridge
could have been connected to another CPU with appropriate interfacing,
but that never happened.

The thing to realise is that the Footbridge is a little more than just
a pure PCI bridge.  It's also the SDRAM controller, UART port and
provides support for a non-PCI expansion bus.

Probably the best model which represents it is in actual fact the x86
PC in years gone by.  The separate processor (StrongARM) with the PCI
northbridge (Footbridge) which couples the processor to the rest of
the system.  Some Footbridge systems really do approximate the x86
PC with a southbridge attached (eg, Netwinder did this, with a real
southbridge providing keyboard, mouse, bridge to the ISA bus, IDE etc).

You could also think of it as an early SoC which hasn't quite integrated
the CPU, as the Footbridge defines quite a lot about how the physical
system memory map looks.

The difference between the CO285 and the EBSA285 is that CO285 was
exclusively add-in mode (in other words, CO285 was Linux running on
a DC21285 based card you could plug into your PC and wanted to map
large spaces of PCI memory space) whereas the EBSA285 was the much
smaller end of the add-in mode, and also host mode (StrongARM being
responsible for PCI configuration etc.)

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