On Fri, Feb 10, 2017 at 10:56:12PM +0000, Hartley Sweeten wrote:
On Friday, February 10, 2017 3:45 PM, Alexander Clouter wrote:
On Fri, Feb 10, 2017 at 11:11:54AM -0700, H Hartley Sweeten wrote:
Currently the ts78xx platform does some "probing" of the rtc NVRAM to see
if it is actually present before registering the rtc device. This "probing"
just checks if the NVRAM is present by reading/writing the last two bytes
of the NVRAM. I'm not sure if this is really necessary. If it can be removed
all the m48t86_ops stuff could also be removed from this driver, along with
platform_data/rtc-m48t86.h.
The RTC is an optional upgrade on the TS-7800[1]. Not sure what would happen
if the RTC driver kicks in with no actual RTC being present?
How about modifying the m48t86 probe so that it does the NVRAM check that
you are doing in the ts78xx platform code. If the NVRAM check fails the probe
will return -ENODEV. Reading the NVRAM to check the 0x55 0xaa signature in
the last locations might be adequate. Not sure if making sure they can be
written
is necessary.
Its not a signature, its just some spare usable bytes at the end of the NVRAM;
I cribbed the probing routing from Technologic Systems[1]. They seem to use a
similar routine[2] for the TS-7200 too.
Looks like it would be fine to move this all into the driver its-self.
Cheers
[1] ftp://ftp.embeddedarm.com/ts-arm-sbc/ts-7800-linux/samples/rtc7800.c
[2] ftp://ftp.embeddedarm.com/ts-arm-sbc/ts-7200-linux/sources/rtc.c
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