On Fri, Feb 19, 2016 at 11:43:50AM +0530, Raveendra Padasalagi wrote: > On Thu, Feb 18, 2016 at 8:06 PM, Rob Herring <[email protected]> wrote: > > On Wed, Feb 17, 2016 at 03:13:44PM +0530, Raveendra Padasalagi wrote: > >> 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 <[email protected]> > >> Reviewed-by: Ray Jui <[email protected]> > >> Reviewed-by: Scott Branden <[email protected]> > >> --- > >> .../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
