[PATCH v9 1/8] drm/tilcdc: ensure nonatomic iowrite64 is not used

[Logan Gunthorpe]

Add a check to ensure iowrite64 is only used if it is atomic.

It was decided in [1] that the tilcdc driver should not be using an
atomic operation (so it was left out of this patchset). However, it turns
out that through the drm code, a nonatomic header is actually included:

include/linux/io-64-nonatomic-lo-hi.h
is included from include/drm/drm_os_linux.h:9:0,
from include/drm/drmP.h:74,
from include/drm/drm_modeset_helper.h:26,
from include/drm/drm_atomic_helper.h:33,
from drivers/gpu/drm/tilcdc/tilcdc_crtc.c:19:

And thus, without this change, this patchset would inadvertantly
change the behaviour of the tilcdc driver.

[1] 
lkml.kernel.org/r/cak8p3a2hho_zcnstzq7hmwsz5la5thu19fwzpun16imnyyn...@mail.gmail.com

Signed-off-by: Logan Gunthorpe 
Reviewed-by: Andy Shevchenko 
Cc: Jyri Sarha 
Cc: Arnd Bergmann 
Cc: Tomi Valkeinen 
Cc: David Airlie 
---
 drivers/gpu/drm/tilcdc/tilcdc_regs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_regs.h 
b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
index 9d528c0a67a4..5048ebb86835 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_regs.h
+++ b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
@@ -133,7 +133,7 @@ static inline void tilcdc_write64(struct drm_device *dev, 
u32 reg, u64 data)
struct tilcdc_drm_private *priv = dev->dev_private;
volatile void __iomem *addr = priv->mmio + reg;
 
-#ifdef iowrite64
+#if defined(iowrite64) && !defined(iowrite64_is_nonatomic)
iowrite64(data, addr);
 #else
__iowmb();
-- 
2.11.0

Re: [PATCH v9 1/8] drm/tilcdc: ensure nonatomic iowrite64 is not used

[Jyri Sarha]

On 12/06/17 01:30, Logan Gunthorpe wrote:
> Add a check to ensure iowrite64 is only used if it is atomic.
> 
> It was decided in [1] that the tilcdc driver should not be using an
> atomic operation (so it was left out of this patchset). However, it turns
> out that through the drm code, a nonatomic header is actually included:
> 
> include/linux/io-64-nonatomic-lo-hi.h
> is included from include/drm/drm_os_linux.h:9:0,
> from include/drm/drmP.h:74,
> from include/drm/drm_modeset_helper.h:26,
> from include/drm/drm_atomic_helper.h:33,
> from drivers/gpu/drm/tilcdc/tilcdc_crtc.c:19:
> 
> And thus, without this change, this patchset would inadvertantly
> change the behaviour of the tilcdc driver.
> 
> [1] 
> lkml.kernel.org/r/cak8p3a2hho_zcnstzq7hmwsz5la5thu19fwzpun16imnyyn...@mail.gmail.com
> 
> Signed-off-by: Logan Gunthorpe 
> Reviewed-by: Andy Shevchenko 
> Cc: Jyri Sarha 
> Cc: Arnd Bergmann 
> Cc: Tomi Valkeinen 
> Cc: David Airlie 

I guess it is about time for me to pick this up for the next pull request.

Thanks,
Jyri

> ---
>  drivers/gpu/drm/tilcdc/tilcdc_regs.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_regs.h 
> b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> index 9d528c0a67a4..5048ebb86835 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> @@ -133,7 +133,7 @@ static inline void tilcdc_write64(struct drm_device *dev, 
> u32 reg, u64 data)
>   struct tilcdc_drm_private *priv = dev->dev_private;
>   volatile void __iomem *addr = priv->mmio + reg;
>  
> -#ifdef iowrite64
> +#if defined(iowrite64) && !defined(iowrite64_is_nonatomic)
>   iowrite64(data, addr);
>  #else
>   __iowmb();
> 


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[PATCH v9 1/8] drm/tilcdc: ensure nonatomic iowrite64 is not used

[Logan Gunthorpe]

Add a check to ensure iowrite64 is only used if it is atomic.

It was decided in [1] that the tilcdc driver should not be using an
atomic operation (so it was left out of this patchset). However, it turns
out that through the drm code, a nonatomic header is actually included:

include/linux/io-64-nonatomic-lo-hi.h
is included from include/drm/drm_os_linux.h:9:0,
from include/drm/drmP.h:74,
from include/drm/drm_modeset_helper.h:26,
from include/drm/drm_atomic_helper.h:33,
from drivers/gpu/drm/tilcdc/tilcdc_crtc.c:19:

And thus, without this change, this patchset would inadvertantly
change the behaviour of the tilcdc driver.

[1] 
lkml.kernel.org/r/cak8p3a2hho_zcnstzq7hmwsz5la5thu19fwzpun16imnyyn...@mail.gmail.com

Signed-off-by: Logan Gunthorpe 
Reviewed-by: Andy Shevchenko 
Cc: Jyri Sarha 
Cc: Arnd Bergmann 
Cc: Tomi Valkeinen 
Cc: David Airlie 
---
 drivers/gpu/drm/tilcdc/tilcdc_regs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_regs.h 
b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
index 9d528c0a67a4..5048ebb86835 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_regs.h
+++ b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
@@ -133,7 +133,7 @@ static inline void tilcdc_write64(struct drm_device *dev, 
u32 reg, u64 data)
struct tilcdc_drm_private *priv = dev->dev_private;
volatile void __iomem *addr = priv->mmio + reg;
 
-#ifdef iowrite64
+#if defined(iowrite64) && !defined(iowrite64_is_nonatomic)
iowrite64(data, addr);
 #else
__iowmb();
-- 
2.11.0