On Fri, Feb 19, 2016 at 11:43:50AM +0530, Raveendra Padasalagi wrote:

On Thu, Feb 18, 2016 at 8:06 PM, Rob Herring [off-list ref] wrote:

quoted

On Wed, Feb 17, 2016 at 03:13:44PM +0530, Raveendra Padasalagi wrote:

quoted

In Cygnus SOC touch screen controller registers are shared
with ADC and flex timer. Using readl/writel could lead to
race condition. So touch screen driver is enhanced to support

1. If touchscreen register's are not shared. Register access
is handled through readl/writel if "brcm,iproc-touchscreen"
compatible is provided in touchscreen dt node. This will help
for future SOC's if comes with dedicated touchscreen IP register's.

2. If touchscreen register's are shared with other IP's, register
access is handled through syscon framework API's to take care of
mutually exclusive access. This feature can be enabled by selecting
"brcm,iproc-touchscreen-syscon" compatible string in the touchscreen
dt node.

Hence touchscreen dt node bindings document is updated to take care
of above changes in the touchscreen driver.

Signed-off-by: Raveendra Padasalagi <redacted>
Reviewed-by: Ray Jui <redacted>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
---
 .../input/touchscreen/brcm,iproc-touchscreen.txt   | 57 +++++++++++++++++++---
 1 file changed, 51 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/brcm,iproc-touchscreen.txt b/Documentation/devicetree/bindings/input/touchscreen/brcm,iproc-touchscreen.txt
index 34e3382..f530c25 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/brcm,iproc-touchscreen.txt
+++ b/Documentation/devicetree/bindings/input/touchscreen/brcm,iproc-touchscreen.txt

@@ -1,12 +1,30 @@
 * Broadcom's IPROC Touchscreen Controller

 Required properties:
-- compatible: must be "brcm,iproc-touchscreen"
-- reg: physical base address of the controller and length of memory mapped
-  region.
+- compatible: should be one of
+        "brcm,iproc-touchscreen"
+        "brcm,iproc-touchscreen-syscon"

More specific and this is not how you do syscon. Either the block is or
isn't. You can't have it both ways.

Existing driver has support for reg, if we modify now to support only syscon
then this driver will not work if some one wishes to use previous
kernel version's
dt and vice versa. Basically this breaks dt compatibility. Is that ok ?

But the issue is that the driver does not actually work correctly with
direct register access on those systems, since the registers are
actually shared with other components. I am not quite sure if it is OK
to break DT binding in this case...

Thanks.

-- 
Dmitry