[PATCH] amba: tegra-ahb: mark PM functions as __maybe_unused

[PATCH] amba: tegra-ahb: mark PM functions as __maybe_unused

[Arnd Bergmann]

clang warns about an unused variable when CONFIG_PM is disabled,
since it is only referenced from an #ifdef:

drivers/amba/tegra-ahb.c:97:18: error: variable 'tegra_ahb_gizmo' is not needed and will not be emitted [-Werror,-Wunneeded-internal-declaration]

Rather than trying to get the #ifdef right, remove it and
use __maybe_unused here, which is less error prone.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/amba/tegra-ahb.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/amba/tegra-ahb.c b/drivers/amba/tegra-ahb.c
index b0b688c481e8..3751d811be39 100644
--- a/drivers/amba/tegra-ahb.c
+++ b/drivers/amba/tegra-ahb.c
@@ -170,8 +170,7 @@ int tegra_ahb_enable_smmu(struct device_node *dn)
 EXPORT_SYMBOL(tegra_ahb_enable_smmu);
 #endif
 
-#ifdef CONFIG_PM
-static int tegra_ahb_suspend(struct device *dev)
+static int __maybe_unused tegra_ahb_suspend(struct device *dev)
 {
 	int i;
 	struct tegra_ahb *ahb = dev_get_drvdata(dev);
@@ -181,7 +180,7 @@ static int tegra_ahb_suspend(struct device *dev)
 	return 0;
 }
 
-static int tegra_ahb_resume(struct device *dev)
+static int __maybe_unused tegra_ahb_resume(struct device *dev)
 {
 	int i;
 	struct tegra_ahb *ahb = dev_get_drvdata(dev);
@@ -190,7 +189,6 @@ static int tegra_ahb_resume(struct device *dev)
 		gizmo_writel(ahb, ahb->ctx[i], tegra_ahb_gizmo[i]);
 	return 0;
 }
-#endif
 
 static UNIVERSAL_DEV_PM_OPS(tegra_ahb_pm,
 			    tegra_ahb_suspend,
-- 
2.20.0

Re: [PATCH] amba: tegra-ahb: mark PM functions as __maybe_unused

[Thierry Reding]

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On Fri, Apr 26, 2019 at 04:56:03PM +0200, Arnd Bergmann wrote:
> clang warns about an unused variable when CONFIG_PM is disabled,
> since it is only referenced from an #ifdef:
> 
> drivers/amba/tegra-ahb.c:97:18: error: variable 'tegra_ahb_gizmo' is not needed and will not be emitted [-Werror,-Wunneeded-internal-declaration]
> 
> Rather than trying to get the #ifdef right, remove it and
> use __maybe_unused here, which is less error prone.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/amba/tegra-ahb.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)

Shouldn't tegra_ahb_gizmo have the same annotation, then? I do see that
it's "used" in tegra_ahb_probe() as part of an ARRAY_SIZE() expression,
but that technically doesn't mean that it would need to be emitted, but
it might be enough to shut up clang?

Or does the __maybe_unused not get propagated?

Looking at the code, I guess we could save a bit of memory if we didn't
allocate memory for the zero-length "ctx" array for !PM since that's no
longer needed. But then again, we've recently changed 32-bit Tegra to
forcefully enable PM, just like we did for 64-bit Tegra, so that's moot
anyway.

Do you want me to pick this up, or would you rather stash it into ARM
SoC directly? If the latter:

Acked-by: Thierry Reding <treding@nvidia.com>

> diff --git a/drivers/amba/tegra-ahb.c b/drivers/amba/tegra-ahb.c
> index b0b688c481e8..3751d811be39 100644
> --- a/drivers/amba/tegra-ahb.c
> +++ b/drivers/amba/tegra-ahb.c
> @@ -170,8 +170,7 @@ int tegra_ahb_enable_smmu(struct device_node *dn)
>  EXPORT_SYMBOL(tegra_ahb_enable_smmu);
>  #endif
>  
> -#ifdef CONFIG_PM
> -static int tegra_ahb_suspend(struct device *dev)
> +static int __maybe_unused tegra_ahb_suspend(struct device *dev)
>  {
>  	int i;
>  	struct tegra_ahb *ahb = dev_get_drvdata(dev);
> @@ -181,7 +180,7 @@ static int tegra_ahb_suspend(struct device *dev)
>  	return 0;
>  }
>  
> -static int tegra_ahb_resume(struct device *dev)
> +static int __maybe_unused tegra_ahb_resume(struct device *dev)
>  {
>  	int i;
>  	struct tegra_ahb *ahb = dev_get_drvdata(dev);
> @@ -190,7 +189,6 @@ static int tegra_ahb_resume(struct device *dev)
>  		gizmo_writel(ahb, ahb->ctx[i], tegra_ahb_gizmo[i]);
>  	return 0;
>  }
> -#endif
>  
>  static UNIVERSAL_DEV_PM_OPS(tegra_ahb_pm,
>  			    tegra_ahb_suspend,
> -- 
> 2.20.0
> 

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Re: [PATCH] amba: tegra-ahb: mark PM functions as __maybe_unused

[Arnd Bergmann]

On Fri, Apr 26, 2019 at 5:20 PM Thierry Reding <thierry.reding@gmail.com> wrote:
>
> On Fri, Apr 26, 2019 at 04:56:03PM +0200, Arnd Bergmann wrote:
> > clang warns about an unused variable when CONFIG_PM is disabled,
> > since it is only referenced from an #ifdef:
> >
> > drivers/amba/tegra-ahb.c:97:18: error: variable 'tegra_ahb_gizmo' is not needed and will not be emitted [-Werror,-Wunneeded-internal-declaration]
> >
> > Rather than trying to get the #ifdef right, remove it and
> > use __maybe_unused here, which is less error prone.
> >
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> >  drivers/amba/tegra-ahb.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
>
> Shouldn't tegra_ahb_gizmo have the same annotation, then? I do see that
> it's "used" in tegra_ahb_probe() as part of an ARRAY_SIZE() expression,
> but that technically doesn't mean that it would need to be emitted, but
> it might be enough to shut up clang?

It would be enough to annotated tegra_ahb_gizmo as __maybe_unused,
but I don't like the idea of using both __maybe_unused and #ifdef to
deal with the CONFIG_PM issue, so I was try to make this more consistent.

> Or does the __maybe_unused not get propagated?
>
> Looking at the code, I guess we could save a bit of memory if we didn't
> allocate memory for the zero-length "ctx" array for !PM since that's no
> longer needed. But then again, we've recently changed 32-bit Tegra to
> forcefully enable PM, just like we did for 64-bit Tegra, so that's moot
> anyway.

Right

> Do you want me to pick this up, or would you rather stash it into ARM
> SoC directly? If the latter:

Olof is currently doing the merges and I forgot to Cc him, so I'd prefer
if you could forward the patch to him or include it in a later pull
request.

        Arnd