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Date:   Tue,  5 Dec 2017 16:30:51 -0700
From:   Logan Gunthorpe <>
Cc:     Arnd Bergmann <>,
        Greg Kroah-Hartman <>,
        Andy Shevchenko <>,
        Horia Geantă <>,
        Logan Gunthorpe <>,
        Jyri Sarha <>,
        Tomi Valkeinen <>,
        David Airlie <>
Subject: [PATCH v9 1/8] drm/tilcdc: ensure nonatomic iowrite64 is not used

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 <>
 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);

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