[PATCH] drm/amdgpu: Initialize shadow to false in gfx_v9_0_rlcg_wreg

[Nathan Chancellor]

clang warns:

drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
is used uninitialized whenever 'if' condition is
false [-Wsometimes-uninitialized]
if (offset == grbm_cntl || offset == grbm_idx)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
occurs here
if (shadow) {
^~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:2: note: remove the 'if' if
its condition is always true
if (offset == grbm_cntl || offset == grbm_idx)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:738:13: note: initialize the
variable 'shadow' to silence this warning
bool shadow;
^
= 0
1 warning generated.

It is not wrong so initialize shadow to false to ensure shadow is always
used initialized.

Fixes: 2e0cc4d48b91 ("drm/amdgpu: revise RLCG access path")
Link: https://github.com/ClangBuiltLinux/linux/issues/936
Signed-off-by: Nathan Chancellor <natecha...@gmail.com>
---
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
index 7bc2486167e7..affbff76758c 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
@@ -735,7 +735,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
static void *spare_int;
static uint32_t grbm_cntl;
static uint32_t grbm_idx;
- bool shadow;
+ bool shadow = false;

scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;
--
2.26.0.rc1

[Nick Desaulniers]

On Tue, Mar 17, 2020 at 5:25 PM Nathan Chancellor
<natecha...@gmail.com> wrote:
>
> clang warns:
>
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
> is used uninitialized whenever 'if' condition is
> false [-Wsometimes-uninitialized]
> if (offset == grbm_cntl || offset == grbm_idx)
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
> occurs here
> if (shadow) {
> ^~~~~~
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:2: note: remove the 'if' if
> its condition is always true
> if (offset == grbm_cntl || offset == grbm_idx)
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:738:13: note: initialize the
> variable 'shadow' to silence this warning
> bool shadow;
> ^
> = 0
> 1 warning generated.
>
> It is not wrong so initialize shadow to false to ensure shadow is always
> used initialized.

Yep, thanks for the patch.
Reviewed-by: Nick Desaulniers <ndesau...@google.com>

>
> Fixes: 2e0cc4d48b91 ("drm/amdgpu: revise RLCG access path")
> Link: https://github.com/ClangBuiltLinux/linux/issues/936
> Signed-off-by: Nathan Chancellor <natecha...@gmail.com>
> ---
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> index 7bc2486167e7..affbff76758c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> @@ -735,7 +735,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
> static void *spare_int;
> static uint32_t grbm_cntl;
> static uint32_t grbm_idx;
> - bool shadow;
> + bool shadow = false;
>
> scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
> scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;
> --
> 2.26.0.rc1
>

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--
Thanks,
~Nick Desaulniers

[Joe Perches]

On Tue, 2020-03-17 at 17:25 -0700, Nathan Chancellor wrote:
> clang warns:
>
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
> is used uninitialized whenever 'if' condition is
> false [-Wsometimes-uninitialized]
> if (offset == grbm_cntl || offset == grbm_idx)
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
> occurs here
> if (shadow) {
> ^~~~~~

Wouldn't it be better to get rid of the shadow variable completely?
---
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
index 7bc248..496b9e 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
@@ -735,7 +735,6 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)

static void *spare_int;
static uint32_t grbm_cntl;
static uint32_t grbm_idx;
- bool shadow;

scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;

@@ -751,10 +750,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
return;
}

- if (offset == grbm_cntl || offset == grbm_idx)
- shadow = true;
-
- if (shadow) {
+ if (offset == grbm_cntl || offset == grbm_idx) {
if (offset == grbm_cntl)
writel(v, scratch_reg2);
else if (offset == grbm_idx)

[Nick Desaulniers]

On Wed, Mar 18, 2020 at 1:28 PM Joe Perches <j...@perches.com> wrote:
>
> On Tue, 2020-03-17 at 17:25 -0700, Nathan Chancellor wrote:
> > clang warns:
> >
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
> > is used uninitialized whenever 'if' condition is
> > false [-Wsometimes-uninitialized]
> > if (offset == grbm_cntl || offset == grbm_idx)
> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
> > occurs here
> > if (shadow) {
> > ^~~~~~
>
> Wouldn't it be better to get rid of the shadow variable completely?

Yes, much better indeed. Seems it only has one use.

> ---
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> index 7bc248..496b9e 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> @@ -735,7 +735,6 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
> static void *spare_int;
> static uint32_t grbm_cntl;
> static uint32_t grbm_idx;
> - bool shadow;
>
> scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
> scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;
> @@ -751,10 +750,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
> return;
> }
>
> - if (offset == grbm_cntl || offset == grbm_idx)
> - shadow = true;
> -
> - if (shadow) {
> + if (offset == grbm_cntl || offset == grbm_idx) {
> if (offset == grbm_cntl)
> writel(v, scratch_reg2);
> else if (offset == grbm_idx)
>
>

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--
Thanks,
~Nick Desaulniers

[Nathan Chancellor]

clang warns:

drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
is used uninitialized whenever 'if' condition is
false [-Wsometimes-uninitialized]
if (offset == grbm_cntl || offset == grbm_idx)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
occurs here
if (shadow) {
^~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:2: note: remove the 'if' if
its condition is always true
if (offset == grbm_cntl || offset == grbm_idx)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:738:13: note: initialize the
variable 'shadow' to silence this warning
bool shadow;
^
= 0
1 warning generated.

shadow is only assigned in one condition and used as the condition for
another if statement; combine the two if statements and remove shadow
to make the code cleaner and resolve this warning.

Fixes: 2e0cc4d48b91 ("drm/amdgpu: revise RLCG access path")
Link: https://github.com/ClangBuiltLinux/linux/issues/936

Suggested-by: Joe Perches <j...@perches.com>
Reviewed-by: Nick Desaulniers <ndesau...@google.com>

Signed-off-by: Nathan Chancellor <natecha...@gmail.com>
---

v1 -> v2:

* Remove shadow altogether, as suggested by Joe Perches.
* Add Nick's Reviewed-by, as I assume it still stands.

drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
index 7bc2486167e7..496b9edca3c3 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
@@ -735,7 +735,6 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)

static void *spare_int;
static uint32_t grbm_cntl;
static uint32_t grbm_idx;
- bool shadow;

scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;

@@ -751,10 +750,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
return;
}

- if (offset == grbm_cntl || offset == grbm_idx)
- shadow = true;
-
- if (shadow) {
+ if (offset == grbm_cntl || offset == grbm_idx) {
if (offset == grbm_cntl)
writel(v, scratch_reg2);
else if (offset == grbm_idx)
--

2.26.0.rc1

[Nick Desaulniers]

yep, thanks

--
Thanks,
~Nick Desaulniers

[Alex Deucher]

Applied. thanks!

Alex

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