From: Logan Gunthorpe <>

[ Upstream commit 4e5ca2d930aa8714400aedf4bf1dc959cb04280f ]

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.


Signed-off-by: Logan Gunthorpe <>
Reviewed-by: Andy Shevchenko <>
Cc: Jyri Sarha <>
Cc: Arnd Bergmann <>
Cc: Tomi Valkeinen <>
Cc: David Airlie <>
Signed-off-by: Jyri Sarha <>
Signed-off-by: Sasha Levin <>
 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 
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);

Reply via email to