From: Roger Pau Monne Date: Tue, 26 Oct 2021 15:12:33 +0000 (+0200) Subject: x86/hpet: setup HPET even when disabled due to stopping in deep C states X-Git-Tag: archive/raspbian/4.16.0+51-g0941d6cb-1+rpi1~2^2~42^2~52 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=c91c967f329f866b1826b04e73e32aea936930cd;p=xen.git x86/hpet: setup HPET even when disabled due to stopping in deep C states Always allow the HPET to be setup, but don't report a frequency back to the platform time source probe in order to avoid it from being selected as a valid timer if it's not usable. Doing the setup even when not intended to be used as a platform timer is required so that is can be used in legacy replacement mode in order to assert the IO-APIC is capable of receiving interrupts. Fixes: c12731493a ('x86/hpet: Use another crystalball to evaluate HPET usability') Reported-by: Andrew Cooper Signed-off-by: Roger Pau Monné Acked-by: Andrew Cooper Tested-by: Andrew Cooper Release-Acked-by: Ian Jackson --- diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index cbadaa036f..a290aba3e8 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -379,6 +379,12 @@ static int64_t __init init_hpet(struct platform_timesource *pts) { uint64_t hpet_rate, start; uint32_t count, target; + /* + * Allow HPET to be setup, but report a frequency of 0 so it's not selected + * as a timer source. This is required so it can be used in legacy + * replacement mode in check_timer. + */ + bool disable_hpet = false; if ( hpet_address && strcmp(opt_clocksource, pts->id) && cpuidle_using_deep_cstate() ) @@ -391,7 +397,7 @@ static int64_t __init init_hpet(struct platform_timesource *pts) case 0x0f1c: /* HPET on Cherry Trail platforms will halt in deep C states. */ case 0x229c: - hpet_address = 0; + disable_hpet = true; break; } @@ -431,14 +437,14 @@ static int64_t __init init_hpet(struct platform_timesource *pts) else if ( !strcmp(opt_clocksource, pts->id) ) printk("HPET use requested via command line, but dysfunctional in PC10\n"); else - hpet_address = 0; + disable_hpet = true; } - if ( !hpet_address ) + if ( disable_hpet ) printk("Disabling HPET for being unreliable\n"); } - if ( (hpet_rate = hpet_setup()) == 0 ) + if ( (hpet_rate = hpet_setup()) == 0 || disable_hpet ) return 0; pts->frequency = hpet_rate;