Patch "drm/tilcdc: ensure nonatomic iowrite64 is not used" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

drm/tilcdc: ensure nonatomic iowrite64 is not used

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-tilcdc-ensure-nonatomic-iowrite64-is-not-used.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Logan Gunthorpe <[email protected]>
Date: Tue, 5 Dec 2017 16:30:51 -0700
Subject: drm/tilcdc: ensure nonatomic iowrite64 is not used

From: Logan Gunthorpe <[email protected]>

[ 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:

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_zCnsTzq7hmWSz5La5Thu19FWZpun16iMnyyNreQ@mail.gmail.com

---
 drivers/gpu/drm/tilcdc/tilcdc_regs.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -124,7 +124,7 @@ static inline void tilcdc_write64(struct
 	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();

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/drm-tilcdc-ensure-nonatomic-iowrite64-is-not-used.patch