[PATCH v2 RESEND 1/3] clocksource/vt8500: Use MIN_OSCR_DELTA from PXA

Roman Volkov [off-list ref] writes:

? Thu, 31 Dec 2015 23:33:45 +0100 (CET)
Thomas Gleixner [off-list ref] ?????:

quoted

Roman,

On Thu, 31 Dec 2015, Roman Volkov wrote:

quoted

Since vt8500 and PXA timers are identical, use MIN_OSCR_DELTA from
PXA, which is bigger than existing value. It is required to
determine the minimum delay which hardware can generate.  

Now that brings up the obvious question:

If the vt8500 and PXA timers are identical why has vt8500 it's own
slightly different implementation and does not use the PXA timer?

Thomas,

I occasionally noticed that the PXA can be reused, when working on the
bugfix for vt8500. Another good question would be how exactly this code
can be reused. We may rework PXA driver to make it working under
vt8500, or include the C code from the vt8500 and get two slightly
different modules. You may look at our previous discussion with Alexey:

https://lkml.org/lkml/2015/12/21/437

Adding Robert and Bill to get more opinions. At this step, fixing the
vt8500 nanosleep bug is a priority.

Personnaly I'm not very thrilled by combining pxa and vt8500 drivers into one.

The rationale I have behind is that :
 - the new driver will have new ifs to switch form vt8500 to pxa
   For example, suspend/resume functions will be different.
   Moreover in order to not impact the pxa runtime some ifs will be necessary
   (will that be if (IS_ENABLED(CONFIG_ARCH_PXA) && ...)
 - the IPs do not look that similar to me
   They seems inter-operable, but that seems to me to be just because of the 3
   common register placement : register at match (@0x00), counter (@0x10) and
   interrupt enabled (@0x1c).
   The register acces semantics are different (vt8500 needs a bit to access),
   the input clock seems different.

For ~140 lines of code, I prefer the simplicity brought by drivers
separation. The diffstat should be pretty equivalent between 2 drivers and 1
combined driver with many ifs.

Cheers.

-- 
Robert