* [PATCH] dmaengine: xilinx_dma: Fix __aligned attribute on zynqmp_dma_desc_ll
@ 2018-09-11 23:05 Nathan Chancellor
2018-09-11 23:37 ` Nick Desaulniers
0 siblings, 1 reply; 3+ messages in thread
From: Nathan Chancellor @ 2018-09-11 23:05 UTC (permalink / raw)
To: Dan Williams, Vinod Koul
Cc: Kedareswara rao Appana, dmaengine, linux-kernel,
Nick Desaulniers, Nathan Chancellor
Clang warns:
drivers/dma/xilinx/zynqmp_dma.c:166:4: warning: attribute 'aligned' is
ignored, place it after "struct" to apply attribute to type declaration
[-Wignored-attributes]
}; __aligned(64)
^
./include/linux/compiler_types.h:200:38: note: expanded from macro
'__aligned'
#define __aligned(x) __attribute__((aligned(x)))
^
1 warning generated.
Place __aligned before the semicolon.
Fixes: b0cc417c1637 ("dmaengine: Add Xilinx zynqmp dma engine driver support")
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
drivers/dma/xilinx/zynqmp_dma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
index c74a88b65039..dc19d67cb8c1 100644
--- a/drivers/dma/xilinx/zynqmp_dma.c
+++ b/drivers/dma/xilinx/zynqmp_dma.c
@@ -163,7 +163,7 @@ struct zynqmp_dma_desc_ll {
u32 ctrl;
u64 nxtdscraddr;
u64 rsvd;
-}; __aligned(64)
+} __aligned(64);
/**
* struct zynqmp_dma_desc_sw - Per Transaction structure
--
2.18.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] dmaengine: xilinx_dma: Fix __aligned attribute on zynqmp_dma_desc_ll
2018-09-11 23:05 [PATCH] dmaengine: xilinx_dma: Fix __aligned attribute on zynqmp_dma_desc_ll Nathan Chancellor
@ 2018-09-11 23:37 ` Nick Desaulniers
2018-09-11 23:48 ` Nathan Chancellor
0 siblings, 1 reply; 3+ messages in thread
From: Nick Desaulniers @ 2018-09-11 23:37 UTC (permalink / raw)
To: Nathan Chancellor
Cc: dan.j.williams, vkoul, appana.durga.rao, dmaengine, LKML
On Tue, Sep 11, 2018 at 4:06 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> Clang warns:
>
> drivers/dma/xilinx/zynqmp_dma.c:166:4: warning: attribute 'aligned' is
> ignored, place it after "struct" to apply attribute to type declaration
> [-Wignored-attributes]
> }; __aligned(64)
> ^
> ./include/linux/compiler_types.h:200:38: note: expanded from macro
> '__aligned'
> #define __aligned(x) __attribute__((aligned(x)))
> ^
> 1 warning generated.
>
> Place __aligned before the semicolon.
>
> Fixes: b0cc417c1637 ("dmaengine: Add Xilinx zynqmp dma engine driver support")
> Reported-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> drivers/dma/xilinx/zynqmp_dma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
> index c74a88b65039..dc19d67cb8c1 100644
> --- a/drivers/dma/xilinx/zynqmp_dma.c
> +++ b/drivers/dma/xilinx/zynqmp_dma.c
> @@ -163,7 +163,7 @@ struct zynqmp_dma_desc_ll {
> u32 ctrl;
> u64 nxtdscraddr;
> u64 rsvd;
> -}; __aligned(64)
> +} __aligned(64);
Thanks for this patch Nathan. Thinking more about this...the integer
passed to __attribute__((aligned(x))) should be in terms of bytes. 64
bytes seems kind of high. Maybe they meant 64 *bits* thus 8 *bytes*
which already the default alignment of the struct:
https://godbolt.org/z/7vW6E3
In which case, the correct fix is to remove the `__aligned(64);`
outright. Since that doesn't change anything (thanks to clang's
helpful -Wignored-attributes), such a patch would be "No Functional
Change" (does not change the status quo). Still, it might be good for
the maintainer to remark if 64 *byte* alignment was intentional (I
would think not, but I don't have the datasheet for this piece of
hardware in front of me; never say never) before sending such a patch.
If the 64 *byte* (512 bit) alignment was intentional (again, which I
doubt), then this patch is good to go, but that would then be a
functional change and should be tested by someone with hardware.
>
> /**
> * struct zynqmp_dma_desc_sw - Per Transaction structure
> --
> 2.18.0
>
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] dmaengine: xilinx_dma: Fix __aligned attribute on zynqmp_dma_desc_ll
2018-09-11 23:37 ` Nick Desaulniers
@ 2018-09-11 23:48 ` Nathan Chancellor
0 siblings, 0 replies; 3+ messages in thread
From: Nathan Chancellor @ 2018-09-11 23:48 UTC (permalink / raw)
To: Nick Desaulniers; +Cc: dan.j.williams, vkoul, appana.durga.rao, dmaengine, LKML
On Tue, Sep 11, 2018 at 04:37:48PM -0700, Nick Desaulniers wrote:
> On Tue, Sep 11, 2018 at 4:06 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > Clang warns:
> >
> > drivers/dma/xilinx/zynqmp_dma.c:166:4: warning: attribute 'aligned' is
> > ignored, place it after "struct" to apply attribute to type declaration
> > [-Wignored-attributes]
> > }; __aligned(64)
> > ^
> > ./include/linux/compiler_types.h:200:38: note: expanded from macro
> > '__aligned'
> > #define __aligned(x) __attribute__((aligned(x)))
> > ^
> > 1 warning generated.
> >
> > Place __aligned before the semicolon.
> >
> > Fixes: b0cc417c1637 ("dmaengine: Add Xilinx zynqmp dma engine driver support")
> > Reported-by: Nick Desaulniers <ndesaulniers@google.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> > drivers/dma/xilinx/zynqmp_dma.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
> > index c74a88b65039..dc19d67cb8c1 100644
> > --- a/drivers/dma/xilinx/zynqmp_dma.c
> > +++ b/drivers/dma/xilinx/zynqmp_dma.c
> > @@ -163,7 +163,7 @@ struct zynqmp_dma_desc_ll {
> > u32 ctrl;
> > u64 nxtdscraddr;
> > u64 rsvd;
> > -}; __aligned(64)
> > +} __aligned(64);
>
> Thanks for this patch Nathan. Thinking more about this...the integer
> passed to __attribute__((aligned(x))) should be in terms of bytes. 64
> bytes seems kind of high. Maybe they meant 64 *bits* thus 8 *bytes*
> which already the default alignment of the struct:
> https://godbolt.org/z/7vW6E3
>
> In which case, the correct fix is to remove the `__aligned(64);`
> outright. Since that doesn't change anything (thanks to clang's
> helpful -Wignored-attributes), such a patch would be "No Functional
> Change" (does not change the status quo). Still, it might be good for
> the maintainer to remark if 64 *byte* alignment was intentional (I
> would think not, but I don't have the datasheet for this piece of
> hardware in front of me; never say never) before sending such a patch.
>
> If the 64 *byte* (512 bit) alignment was intentional (again, which I
> doubt), then this patch is good to go, but that would then be a
> functional change and should be tested by someone with hardware.
>
Thanks for the review Nick. If that is indeed the case, I will spin up a v2.
>
> >
> > /**
> > * struct zynqmp_dma_desc_sw - Per Transaction structure
> > --
> > 2.18.0
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-09-11 23:05 [PATCH] dmaengine: xilinx_dma: Fix __aligned attribute on zynqmp_dma_desc_ll Nathan Chancellor
2018-09-11 23:37 ` Nick Desaulniers
2018-09-11 23:48 ` Nathan Chancellor
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