On Fri, Jun 5, 2015 at 2:43 PM, Robert Jarzmik [off-list ref] wrote:

Rob Herring [off-list ref] writes:

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I'm rather in a mood for a more aggressive approach :

 - you fire an incremental patch to patch the 10 defconfigs on PXA architecture
   (pxa27x and pxa3xx)

Here's the breakdown of configs which enable SA1100 RTC only. Only the
last 6 need to change by my count:

pxa25x
arch/arm/configs/h5000_defconfig
arch/arm/configs/xcep_defconfig
arch/arm/configs/viper_defconfig

pxa255/270
arch/arm/configs/cm_x2xx_defconfig

pxa270
arch/arm/configs/em_x270_defconfig
arch/arm/configs/magician_defconfig
arch/arm/configs/palmz72_defconfig
arch/arm/configs/pcm027_defconfig
arch/arm/configs/trizeps4_defconfig

And arch/arm/configs/jornada720_defconfig I counted wrongly as it's sa1100.
So I agree with your list of last 6 defconfigs.

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 - in this patch, you replace 's/CONFIG_RTC_DRV_SA1100/CONFIG_RTC_DRV_PXA/'
 - you send this patch to the maintainers and me
 - you explain in the commit message that from a userland perspective, nothing
   changes, except that the RTC IP will change, and any dependency on a

The IP does not change here. rtc0 is still going to be the SA1100 RTC
being registered first. The only change will be the addition of rtc1.

For boards which were only using rtc-pxa.c (as mioa701 for example), they relied
on the fact that rtc0 == pxa_rtc. Their time is stored in PXA IP. Therefore,
each of their hwclock will end up on sa1100-rtc instead of pxa-rtc.

So for these boards, ie. for all boards where only rtc-pxa.c was used, the IP
addressed changes from a casual userspace perspective.

Okay, so this is the case where the time will be wrong.

I could remove the select of the sa1100-rtc and do an empty function
for sa1100_rtc_init. This would preserve current behavior.

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   bootloader fidling with RTC should be considered as a source of regression.

I'm not sure that I follow.

Let's talk about how a double boot windows + linux box works.
The bootloader ensures that :
 - sa1100-rtc holds the number of seconds since the OS start (think jiffies)
 - pxa-rtc holds the wall clock time

Upon each reboot, sa1100-rtc is checked to see how much time has passed. If an
"oustanding number" is detected, for example 10 years, the firmware resets the
data partition.

Now think what will happen when this change will be commited, upon the first
reboot after the linux kernel has change sa1100-rtc time.

That would be bad. But on these platforms, the kernel has been using
both RTCs right? Presumably on platforms only using 1 of the RTCs, the
bootloader does not touch the RTCs.

Rob

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   Moreover the first reboot will have the wrong date, until it is set.

Only for rtc1, right?

Yes, right, unless the bootloader logic is ... over-engineered.

All of this to say maintainers should be forwarned at least. After that, up to
them to react.

Cheers.

--
Robert