[PATCH] MIPS: Fix CM region target definitions

[PATCH] MIPS: Fix CM region target definitions

[Paul Burton]

The default CM target field in the GCR_BASE register is encoded with 0
meaning memory & 1 being reserved. However the definitions we use for
those bits effectively get these two values backwards - likely because
they were copied from the definitions for the CM regions where the
target is encoded differently. This results in use setting up GCR_BASE
with the reserved target value by default, rather than targeting memory
as intended. Although we currently seem to get away with this it's not a
great idea to rely upon.

Fix this by changing our macros to match the documentated target values.

The incorrect encoding became used as of commit 9f98f3dd0c51 ("MIPS: Add
generic CM probe & access code") in the Linux v3.15 cycle, and was
likely carried forwards from older but unused code introduced by
commit 39b8d5254246 ("[MIPS] Add support for MIPS CMP platform.") in the
v2.6.26 cycle.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Reported-by: Matt Redfearn <matt.redfearn@mips.com>
Cc: Matt Redfearn <matt.redfearn@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # v3.15+
---

 arch/mips/include/asm/mips-cm.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/include/asm/mips-cm.h b/arch/mips/include/asm/mips-cm.h
index f6231b91b724..c6aaabd7cfd1 100644
--- a/arch/mips/include/asm/mips-cm.h
+++ b/arch/mips/include/asm/mips-cm.h
@@ -142,8 +142,8 @@ GCR_ACCESSOR_RO(64, 0x000, config)
 GCR_ACCESSOR_RW(64, 0x008, base)
 #define CM_GCR_BASE_GCRBASE			GENMASK_ULL(47, 15)
 #define CM_GCR_BASE_CMDEFTGT			GENMASK(1, 0)
-#define  CM_GCR_BASE_CMDEFTGT_DISABLED		0
-#define  CM_GCR_BASE_CMDEFTGT_MEM		1
+#define  CM_GCR_BASE_CMDEFTGT_MEM		0
+#define  CM_GCR_BASE_CMDEFTGT_RESERVED		1
 #define  CM_GCR_BASE_CMDEFTGT_IOCU0		2
 #define  CM_GCR_BASE_CMDEFTGT_IOCU1		3
 
-- 
2.15.0

Re: [PATCH] MIPS: Fix CM region target definitions

[James Hogan]

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On Tue, Oct 31, 2017 at 03:09:22PM -0700, Paul Burton wrote:
> The default CM target field in the GCR_BASE register is encoded with 0
> meaning memory & 1 being reserved. However the definitions we use for
> those bits effectively get these two values backwards - likely because
> they were copied from the definitions for the CM regions where the
> target is encoded differently. This results in use setting up GCR_BASE
> with the reserved target value by default, rather than targeting memory
> as intended. Although we currently seem to get away with this it's not a
> great idea to rely upon.
> 
> Fix this by changing our macros to match the documentated target values.
> 
> The incorrect encoding became used as of commit 9f98f3dd0c51 ("MIPS: Add
> generic CM probe & access code") in the Linux v3.15 cycle, and was
> likely carried forwards from older but unused code introduced by
> commit 39b8d5254246 ("[MIPS] Add support for MIPS CMP platform.") in the
> v2.6.26 cycle.
> 
> Signed-off-by: Paul Burton <paul.burton@mips.com>
> Reported-by: Matt Redfearn <matt.redfearn@mips.com>
> Cc: Matt Redfearn <matt.redfearn@mips.com>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: linux-mips@linux-mips.org
> Cc: <stable@vger.kernel.org> # v3.15+

Reviewed-by: James Hogan <jhogan@kernel.org>

Cheers
James

> ---
> 
>  arch/mips/include/asm/mips-cm.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/include/asm/mips-cm.h b/arch/mips/include/asm/mips-cm.h
> index f6231b91b724..c6aaabd7cfd1 100644
> --- a/arch/mips/include/asm/mips-cm.h
> +++ b/arch/mips/include/asm/mips-cm.h
> @@ -142,8 +142,8 @@ GCR_ACCESSOR_RO(64, 0x000, config)
>  GCR_ACCESSOR_RW(64, 0x008, base)
>  #define CM_GCR_BASE_GCRBASE			GENMASK_ULL(47, 15)
>  #define CM_GCR_BASE_CMDEFTGT			GENMASK(1, 0)
> -#define  CM_GCR_BASE_CMDEFTGT_DISABLED		0
> -#define  CM_GCR_BASE_CMDEFTGT_MEM		1
> +#define  CM_GCR_BASE_CMDEFTGT_MEM		0
> +#define  CM_GCR_BASE_CMDEFTGT_RESERVED		1
>  #define  CM_GCR_BASE_CMDEFTGT_IOCU0		2
>  #define  CM_GCR_BASE_CMDEFTGT_IOCU1		3
>  
> -- 
> 2.15.0
> 
> 

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