[PATCH] powerpc: Fix assmption of end_of_DRAM() returns end address

memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Signed-off-by: Bharat Bhushan <redacted>
---
This patch is based on next branch of https://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc.git

 arch/powerpc/platforms/44x/currituck.c     |    2 +-
 arch/powerpc/platforms/85xx/corenet_ds.c   |    2 +-
 arch/powerpc/platforms/85xx/ge_imp3a.c     |    2 +-
 arch/powerpc/platforms/85xx/mpc8536_ds.c   |    2 +-
 arch/powerpc/platforms/85xx/mpc85xx_ds.c   |    2 +-
 arch/powerpc/platforms/85xx/mpc85xx_mds.c  |    2 +-
 arch/powerpc/platforms/85xx/p1022_ds.c     |    2 +-
 arch/powerpc/platforms/86xx/mpc86xx_hpcn.c |    2 +-
 8 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/44x/currituck.c b/arch/powerpc/platforms/44x/currituck.c
index 583e67f..9f6c33d 100644
--- a/arch/powerpc/platforms/44x/currituck.c
+++ b/arch/powerpc/platforms/44x/currituck.c

@@ -160,7 +160,7 @@ static void __init ppc47x_setup_arch(void)
 	/* No need to check the DMA config as we /know/ our windows are all of
  	 * RAM.  Lets hope that doesn't change */
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > 0xffffffff) {
+	if ((memblock_end_of_DRAM() - 1) > 0xffffffff) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

diff --git a/arch/powerpc/platforms/85xx/corenet_ds.c b/arch/powerpc/platforms/85xx/corenet_ds.c
index dd3617c..925b028 100644
--- a/arch/powerpc/platforms/85xx/corenet_ds.c
+++ b/arch/powerpc/platforms/85xx/corenet_ds.c

@@ -77,7 +77,7 @@ void __init corenet_ds_setup_arch(void)
 #endif
 
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > max) {
+	if ((memblock_end_of_DRAM() - 1) > max) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

diff --git a/arch/powerpc/platforms/85xx/ge_imp3a.c b/arch/powerpc/platforms/85xx/ge_imp3a.c
index 1801462..b6a728b 100644
--- a/arch/powerpc/platforms/85xx/ge_imp3a.c
+++ b/arch/powerpc/platforms/85xx/ge_imp3a.c

@@ -125,7 +125,7 @@ static void __init ge_imp3a_setup_arch(void)
 	mpc85xx_smp_init();
 
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > max) {
+	if ((memblock_end_of_DRAM() - 1) > max) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

diff --git a/arch/powerpc/platforms/85xx/mpc8536_ds.c b/arch/powerpc/platforms/85xx/mpc8536_ds.c
index 585bd22..767c7cf 100644
--- a/arch/powerpc/platforms/85xx/mpc8536_ds.c
+++ b/arch/powerpc/platforms/85xx/mpc8536_ds.c

@@ -75,7 +75,7 @@ static void __init mpc8536_ds_setup_arch(void)
 #endif
 
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > max) {
+	if ((memblock_end_of_DRAM() - 1) > max) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

diff --git a/arch/powerpc/platforms/85xx/mpc85xx_ds.c b/arch/powerpc/platforms/85xx/mpc85xx_ds.c
index 1fd91e9..d30f6c4 100644
--- a/arch/powerpc/platforms/85xx/mpc85xx_ds.c
+++ b/arch/powerpc/platforms/85xx/mpc85xx_ds.c

@@ -173,7 +173,7 @@ static void __init mpc85xx_ds_setup_arch(void)
 	mpc85xx_smp_init();
 
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > max) {
+	if ((memblock_end_of_DRAM() - 1) > max) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

diff --git a/arch/powerpc/platforms/85xx/mpc85xx_mds.c b/arch/powerpc/platforms/85xx/mpc85xx_mds.c
index d208ebc..8e4b094 100644
--- a/arch/powerpc/platforms/85xx/mpc85xx_mds.c
+++ b/arch/powerpc/platforms/85xx/mpc85xx_mds.c

@@ -359,7 +359,7 @@ static void __init mpc85xx_mds_setup_arch(void)
 	mpc85xx_mds_qe_init();
 
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > max) {
+	if ((memblock_end_of_DRAM() - 1) > max) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

diff --git a/arch/powerpc/platforms/85xx/p1022_ds.c b/arch/powerpc/platforms/85xx/p1022_ds.c
index f700c81..74e310b 100644
--- a/arch/powerpc/platforms/85xx/p1022_ds.c
+++ b/arch/powerpc/platforms/85xx/p1022_ds.c

@@ -450,7 +450,7 @@ static void __init p1022_ds_setup_arch(void)
 	mpc85xx_smp_init();
 
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > max) {
+	if ((memblock_end_of_DRAM() - 1) > max) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

diff --git a/arch/powerpc/platforms/86xx/mpc86xx_hpcn.c b/arch/powerpc/platforms/86xx/mpc86xx_hpcn.c
index 3755e61..817245b 100644
--- a/arch/powerpc/platforms/86xx/mpc86xx_hpcn.c
+++ b/arch/powerpc/platforms/86xx/mpc86xx_hpcn.c

@@ -102,7 +102,7 @@ mpc86xx_hpcn_setup_arch(void)
 #endif
 
 #ifdef CONFIG_SWIOTLB
-	if (memblock_end_of_DRAM() > max) {
+	if ((memblock_end_of_DRAM() - 1) > max) {
 		ppc_swiotlb_enable = 1;
 		set_pci_dma_ops(&swiotlb_dma_ops);
 		ppc_md.pci_dma_dev_setup = pci_dma_dev_setup_swiotlb;

-- 
1.7.0.4

On Tue, 2012-06-05 at 19:25 +0530, Bharat Bhushan wrote:

memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Shouldn't we instead fix it the other way around ? IE, make
memblock_end_of_DRAM() does what the name implies, which is to return
the last byte of DRAM, and fix the -other- callers not to make bad
assumptions ?

Cheers,
Ben.

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 06 Jun 2012 08:17:39 +1000

On Tue, 2012-06-05 at 19:25 +0530, Bharat Bhushan wrote:

quoted

memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Shouldn't we instead fix it the other way around ? IE, make
memblock_end_of_DRAM() does what the name implies, which is to return
the last byte of DRAM, and fix the -other- callers not to make bad
assumptions ?

That was my impression too when I saw this patch.

-----Original Message-----
From: David Miller [mailto:davem@davemloft.net]
Sent: Wednesday, June 06, 2012 3:51 AM
To: benh@kernel.crashing.org
Cc: Bhushan Bharat-R65777; linuxppc-dev@lists.ozlabs.org; linux-
kernel@vger.kernel.org; galak@kernel.crashing.org; Bhushan Bharat-R65777
Subject: Re: [PATCH] powerpc: Fix assmption of end_of_DRAM() returns end =

address

=20
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 06 Jun 2012 08:17:39 +1000
=20

quoted

On Tue, 2012-06-05 at 19:25 +0530, Bharat Bhushan wrote:

quoted

memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Shouldn't we instead fix it the other way around ? IE, make
memblock_end_of_DRAM() does what the name implies, which is to return
the last byte of DRAM, and fix the -other- callers not to make bad
assumptions ?

=20
That was my impression too when I saw this patch.

Initially I also intended to do so. I initiated a email on linux-mm@  subje=
ct "memblock_end_of_DRAM()  return end address + 1" and the only response I=
 received from Andrea was:

"
It's normal that "end" means "first byte offset out of the range". End =3D =
not ok.
end =3D start+size.
This is true for vm_end too. So it's better to keep it that way.
My suggestion is to just fix point 1 below and audit the rest :)
"

Thanks
-Bharat

On Wed, 2012-06-06 at 00:46 +0000, Bhushan Bharat-R65777 wrote:

quoted

quoted

quoted

memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Shouldn't we instead fix it the other way around ? IE, make
memblock_end_of_DRAM() does what the name implies, which is to

return

quoted

quoted

the last byte of DRAM, and fix the -other- callers not to make bad
assumptions ?

That was my impression too when I saw this patch.

Initially I also intended to do so. I initiated a email on linux-mm@
subject "memblock_end_of_DRAM()  return end address + 1" and the only
response I received from Andrea was:

"
It's normal that "end" means "first byte offset out of the range". End
= not ok.
end = start+size.
This is true for vm_end too. So it's better to keep it that way.
My suggestion is to just fix point 1 below and audit the rest :)
"

Oh well, I don't care enough to fight this battle in my current state so
unless Dave has more stamina than I have today, I'm ok with the patch.

Cheers,
Ben.

Hi,

On Wed, Jun 06, 2012 at 03:30:17PM +1000, Benjamin Herrenschmidt wrote:

On Wed, 2012-06-06 at 00:46 +0000, Bhushan Bharat-R65777 wrote:

quoted

quoted

quoted

quoted

memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Shouldn't we instead fix it the other way around ? IE, make
memblock_end_of_DRAM() does what the name implies, which is to

return

quoted

quoted

the last byte of DRAM, and fix the -other- callers not to make bad
assumptions ?

That was my impression too when I saw this patch.

Initially I also intended to do so. I initiated a email on linux-mm@
subject "memblock_end_of_DRAM()  return end address + 1" and the only
response I received from Andrea was:

"
It's normal that "end" means "first byte offset out of the range". End
= not ok.
end = start+size.
This is true for vm_end too. So it's better to keep it that way.
My suggestion is to just fix point 1 below and audit the rest :)
"

Oh well, I don't care enough to fight this battle in my current state so

I wish you to get well soon Ben!

unless Dave has more stamina than I have today, I'm ok with the patch.

Well it doesn't really matter in the end what is decided as long as
something is decided :). I was asked through a forward so I only
expressed my preference...

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 06 Jun 2012 15:30:17 +1000

On Wed, 2012-06-06 at 00:46 +0000, Bhushan Bharat-R65777 wrote:

quoted

quoted

quoted

quoted

memblock_end_of_DRAM() returns end_address + 1, not end address.
While some code assumes that it returns end address.

Shouldn't we instead fix it the other way around ? IE, make
memblock_end_of_DRAM() does what the name implies, which is to

return

quoted

quoted

the last byte of DRAM, and fix the -other- callers not to make bad
assumptions ?

That was my impression too when I saw this patch.

Initially I also intended to do so. I initiated a email on linux-mm@
subject "memblock_end_of_DRAM()  return end address + 1" and the only
response I received from Andrea was:

"
It's normal that "end" means "first byte offset out of the range". End
= not ok.
end = start+size.
This is true for vm_end too. So it's better to keep it that way.
My suggestion is to just fix point 1 below and audit the rest :)
"

Oh well, I don't care enough to fight this battle in my current state so
unless Dave has more stamina than I have today, I'm ok with the patch.

I'm definitely without the samina to fight something like this right now :)