On 2014-11-10 11:23, Pali Rohár wrote:
I can also confirm that it works correctly on a number of ASUS and ASrock desktop motherboards with the most recent BIOS updates, and on a Lenovo Thinkpad L540. I can however confirm that it DOES NOT work however on an Acer Aspire V5-131 system, though I had never updated the BIOS on that one, so it may work correctly with a newer BIOS version.On Monday 10 November 2014 12:22:13 Matt Fleming wrote:On Sun, 2014-11-09 at 19:22 +0100, Borislav Petkov wrote:On Sun, Nov 09, 2014 at 06:37:46PM +0100, Pali Rohár wrote:this patch totally disabled efi rfc driver on x86 machines at compile time. But on some x86 machines it working without crash and reading from file /sys/class/rtc/rtc*/since_epoch returns correct information. So why to disable compiling driver on machines where driver working?Sounds like we need an efi=rtc_enable knob for people who what to use it...I'm not so sure. By and large, the EFI runtime Time services just don't work very well on x86. Just because they work sometimes, doesn't actually mean it's a good idea to use them. The one scenario where the time services are useful is early on during boot when we want to get the timezone information. I have vague recollections of someone working on that.On laptop Dell Latitude E6440 with 64bit kernel 3.17-rc6 (where was rtc-efi.ko enabled at compile time for x86) it working fine without crash. So I think that other Dell machines could work too.
I agree, without it you need PC CMOS RTC support to access the RTC on most systems, which in turn means that you have to enable the CSM in the EFI firmware, which is annoying cause you can't easily dual boot windows with secure boot when the CSM is enabled.Maybe problems which were reported are only specific for 32bit UEFI? Or 32bit kernels? And I think that if I know that efi time service working on machine, I should be able to use it with mainline kernel (without hacking Kconfig to enable it and so...).
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