[PATCH v6 1/7] drm/tilcdc: ensure nonatomic iowrite64 is not used

From: Logan Gunthorpe
Date: Thu Aug 03 2017 - 14:31:59 EST

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:

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_zCnsTzq7hmWSz5La5Thu19FWZpun16iMnyyNreQ@xxxxxxxxxxxxxx

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Jyri Sarha <jsarha@xxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
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);