[PATCH] powerpc/85xx: do not force PHYS_64BIT on Freescale reference boards

[PATCH] powerpc/85xx: do not force PHYS_64BIT on Freescale reference boards

[Timur Tabi]

Kconfig option PHYS_64BIT sets the size of phys_addr_t to 64 bits, which
allows support for a 36-bit physical address space.  With this option, the
kernel can support more than 2GB of RAM, but the larger address size
impacts performance slightly.

By including "select PHYS_64BIT" in the Kconfig for a particular board,
that option is forced enabled, and it becomes impossible to create a 32-bit
kernel.  Instead, we should depend on the defconfig to enable this option.
We still build a 36-bit kernel by default, and we also allow users to build
32-bit kernels if they really want.

Signed-off-by: Timur Tabi <timur@freescale.com>
---
 arch/powerpc/configs/corenet32_smp_defconfig |    1 +
 arch/powerpc/platforms/85xx/Kconfig          |    5 -----
 2 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/configs/corenet32_smp_defconfig b/arch/powerpc/configs/corenet32_smp_defconfig
index 4311d02..819c06e 100644
--- a/arch/powerpc/configs/corenet32_smp_defconfig
+++ b/arch/powerpc/configs/corenet32_smp_defconfig
@@ -1,4 +1,5 @@
 CONFIG_PPC_85xx=y
+CONFIG_PHYS_64BIT=y
 CONFIG_SMP=y
 CONFIG_NR_CPUS=8
 CONFIG_EXPERIMENTAL=y
diff --git a/arch/powerpc/platforms/85xx/Kconfig b/arch/powerpc/platforms/85xx/Kconfig
index 12f5932..6dba779 100644
--- a/arch/powerpc/platforms/85xx/Kconfig
+++ b/arch/powerpc/platforms/85xx/Kconfig
@@ -80,7 +80,6 @@ config P1010_RDB
 config P1022_DS
 	bool "Freescale P1022 DS"
 	select DEFAULT_UIMAGE
-	select PHYS_64BIT	# The DTS has 36-bit addresses
 	select SWIOTLB
 	help
 	  This option enables support for the Freescale P1022DS reference board.
@@ -175,7 +174,6 @@ config P2040_RDB
 	bool "Freescale P2040 RDB"
 	select DEFAULT_UIMAGE
 	select PPC_E500MC
-	select PHYS_64BIT
 	select SWIOTLB
 	select MPC8xxx_GPIO
 	select HAS_RAPIDIO
@@ -187,7 +185,6 @@ config P3041_DS
 	bool "Freescale P3041 DS"
 	select DEFAULT_UIMAGE
 	select PPC_E500MC
-	select PHYS_64BIT
 	select SWIOTLB
 	select MPC8xxx_GPIO
 	select HAS_RAPIDIO
@@ -199,7 +196,6 @@ config P4080_DS
 	bool "Freescale P4080 DS"
 	select DEFAULT_UIMAGE
 	select PPC_E500MC
-	select PHYS_64BIT
 	select SWIOTLB
 	select MPC8xxx_GPIO
 	select HAS_RAPIDIO
@@ -214,7 +210,6 @@ config P5020_DS
 	select DEFAULT_UIMAGE
 	select E500
 	select PPC_E500MC
-	select PHYS_64BIT
 	select SWIOTLB
 	select MPC8xxx_GPIO
 	select HAS_RAPIDIO
-- 
1.7.3.4

Re: [PATCH] powerpc/85xx: do not force PHYS_64BIT on Freescale reference boards

[Kumar Gala]

On Nov 3, 2011, at 1:50 PM, Timur Tabi wrote:

> Kconfig option PHYS_64BIT sets the size of phys_addr_t to 64 bits, =
which
> allows support for a 36-bit physical address space.  With this option, =
the
> kernel can support more than 2GB of RAM, but the larger address size
> impacts performance slightly.
>=20
> By including "select PHYS_64BIT" in the Kconfig for a particular =
board,
> that option is forced enabled, and it becomes impossible to create a =
32-bit
> kernel.  Instead, we should depend on the defconfig to enable this =
option.
> We still build a 36-bit kernel by default, and we also allow users to =
build
> 32-bit kernels if they really want.
>=20
> Signed-off-by: Timur Tabi <timur@freescale.com>
> ---
> arch/powerpc/configs/corenet32_smp_defconfig |    1 +
> arch/powerpc/platforms/85xx/Kconfig          |    5 -----
> 2 files changed, 1 insertions(+), 5 deletions(-)

Nak.  For certain boards like P204x-P50xx we only support a 36-bit =
address map.

- k=

Re: [PATCH] powerpc/85xx: do not force PHYS_64BIT on Freescale reference boards

[Timur Tabi]

Kumar Gala wrote:
> Nak.  For certain boards like P204x-P50xx we only support a 36-bit address map.

I understand that we don't supply a 32-bit U-boot or device tree, but is
there any hard requirement that we force 36-bit kernels?  If it's really a
requirement, then adding to the Kconfig of each board doesn't sound like
the best way to enforce this.

-- 
Timur Tabi
Linux kernel developer at Freescale

Re: [PATCH] powerpc/85xx: do not force PHYS_64BIT on Freescale reference boards

[Kumar Gala]

On Nov 3, 2011, at 2:01 PM, Timur Tabi wrote:

> Kumar Gala wrote:
>> Nak.  For certain boards like P204x-P50xx we only support a 36-bit =
address map.
>=20
> I understand that we don't supply a 32-bit U-boot or device tree, but =
is
> there any hard requirement that we force 36-bit kernels?  If it's =
really a
> requirement, then adding to the Kconfig of each board doesn't sound =
like
> the best way to enforce this.

Yes, there is a requirement.  Why would we allow you to build support =
for a board and not have it boot?  The Kconfig is exactly how to enforce =
this.

- k=