Re: Regression: unable to boot after commit bd9240a18edf ("x86/apic: Add TSC_DEADLINE quirk due to errata") - Surface Pro 4 SKL

[Zhang Rui <rui.zhang@intel.com>]

On Mon, 2017-12-18 at 21:28 +0100, Peter Zijlstra wrote:
> Hi, can you see if this makes you Surface boot?
> 
No, it does not boot.

> I tested it on my IVB by making has_legacy_pic() return unconditional
> true.
> 
> [    0.024000] tsc: Unable to calibrate against PIT
> [    0.025000] tsc: using HPET reference calibration
> [    0.026000] tsc: Detected 2792.451 MHz processor
> 
> ---
> 
> 
> diff --git a/arch/x86/include/asm/i8259.h
> b/arch/x86/include/asm/i8259.h
> index c8376b40e882..e2cfc4b52ee4 100644
> --- a/arch/x86/include/asm/i8259.h
> +++ b/arch/x86/include/asm/i8259.h
> @@ -69,6 +69,11 @@ struct legacy_pic {
>  extern struct legacy_pic *legacy_pic;
>  extern struct legacy_pic null_legacy_pic;
>  
> +static inline bool has_legacy_pic(void)
> +{
> +	return legacy_pic == &null_legacy_pic;
> +}
> +
shouldn't this be
	return legacy_pic == &default_legacy_pic;
?

thanks,
rui
>  static inline int nr_legacy_irqs(void)
>  {
>  	return legacy_pic->nr_legacy_irqs;
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 8ea117f8142e..2afc623b2280 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -25,6 +25,7 @@
>  #include <asm/geode.h>
>  #include <asm/apic.h>
>  #include <asm/intel-family.h>
> +#include <asm/i8259.h>
>  
>  unsigned int __read_mostly cpu_khz;	/* TSC clocks / usec, not
> used here */
>  EXPORT_SYMBOL(cpu_khz);
> @@ -363,6 +364,15 @@ static unsigned long pit_calibrate_tsc(u32
> latch, unsigned long ms, int loopmin)
>  	unsigned long tscmin, tscmax;
>  	int pitcnt;
>  
> +	if (!has_legacy_pic()) {
> +		udelay(10 * USEC_PER_MSEC);
> +		udelay(10 * USEC_PER_MSEC);
> +		udelay(10 * USEC_PER_MSEC);
> +		udelay(10 * USEC_PER_MSEC);
> +		udelay(10 * USEC_PER_MSEC);
> +		return ULONG_MAX;
> +	}
> +
>  	/* Set the Gate high, disable speaker */
>  	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
>  
> @@ -487,6 +497,9 @@ static unsigned long quick_pit_calibrate(void)
>  	u64 tsc, delta;
>  	unsigned long d1, d2;
>  
> +	if (!has_legacy_pic())
> +		return 0;
> +
>  	/* Set the Gate high, disable speaker */
>  	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
>