Re: [kvm-unit-tests PATCH V3 4/5] lib/powerpc: Implement generic sleep function for use in unit test

[Suraj Jitindar Singh <sjitindarsingh@gmail.com>]

On Tue, 2016-08-16 at 14:54 +0200, Thomas Huth wrote:
> On 16.08.2016 09:18, Suraj Jitindar Singh wrote:
> > 
> > It would be nice if we had a generic sleep function which could be
> > used
> > in unit tests, add one.
> > 
> > Add the variable tb_hz used to store the time base frequency which
> > is read
> > from the device tree on setup.
> > 
> > Add functions msleep, usleep and sleep in processor.c to sleep for
> > a given
> > number of milliseconds, microseconds and time base ticks
> > respectively.
> You finally called them mdelay, udelay and delay instead, so in case
> you
> respin, please adjust the commit message.
Woops, I'll fix those
> 
> > 
> > Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> > ---
> > 
> > Change Log:
> > 
> > V2 -> V3:
> > 	- Add patch to series
> > 
> > Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> > ---
> >  lib/powerpc/asm/processor.h | 19 +++++++++++++++++++
> >  lib/powerpc/asm/setup.h     |  2 ++
> >  lib/powerpc/processor.c     | 13 +++++++++++++
> >  lib/powerpc/setup.c         | 12 ++++++++++++
> >  4 files changed, 46 insertions(+)
> > 
> > diff --git a/lib/powerpc/asm/processor.h
> > b/lib/powerpc/asm/processor.h
> > index 09692bd..9554e08 100644
> > --- a/lib/powerpc/asm/processor.h
> > +++ b/lib/powerpc/asm/processor.h
> > @@ -1,11 +1,30 @@
> >  #ifndef _ASMPOWERPC_PROCESSOR_H_
> >  #define _ASMPOWERPC_PROCESSOR_H_
> >  
> > +#include <libcflat.h>
> >  #include <asm/ptrace.h>
> >  
> > +#define cpu_relax() asm volatile ("" : : : "memory")
> I'd maybe add a "nop" instruction in there ... just in case?
We don't put the nop in anywhere else or in the kernel. I'm gonna leave
this.
> 
> > 
> >  #ifndef __ASSEMBLY__
> >  void handle_exception(int trap, void (*func)(struct pt_regs *,
> > void *), void *);
> >  void do_handle_exception(struct pt_regs *regs);
> >  #endif /* __ASSEMBLY__ */
> >  
> > +static inline uint64_t get_tb(void)
> > +{
> > +	uint64_t tb;
> > +	asm volatile ("mfspr %[tb],268" : [tb] "=r" (tb));
> > +	return tb;
> > +}
> > +
> > +extern void delay(uint64_t cycles);
> > +extern void udelay(uint64_t us);
> > +
> > +static inline void mdelay(uint64_t ms)
> > +{
> > +	while (ms--)
> > +		udelay(1000);
> > +}
> > +
> >  #endif /* _ASMPOWERPC_PROCESSOR_H_ */
> > diff --git a/lib/powerpc/asm/setup.h b/lib/powerpc/asm/setup.h
> > index b1e1e5a..23b4156 100644
> > --- a/lib/powerpc/asm/setup.h
> > +++ b/lib/powerpc/asm/setup.h
> > @@ -11,6 +11,8 @@
> >  extern u32 cpus[NR_CPUS];
> >  extern int nr_cpus;
> >  
> > +extern uint64_t tb_hz;
> > +
> >  #define NR_MEM_REGIONS		8
> >  #define MR_F_PRIMARY		(1U << 0)
> >  struct mem_region {
> > diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c
> > index a78bc3c..c84bae5 100644
> > --- a/lib/powerpc/processor.c
> > +++ b/lib/powerpc/processor.c
> > @@ -5,6 +5,7 @@
> >  #include <libcflat.h>
> >  #include <asm/processor.h>
> >  #include <asm/ptrace.h>
> > +#include <asm/setup.h>
> >  
> >  static struct {
> >  	void (*func)(struct pt_regs *, void *data);
> > @@ -36,3 +37,15 @@ void do_handle_exception(struct pt_regs *regs)
> >  	printf("unhandled cpu exception 0x%lx\n", regs->trap);
> >  	abort();
> >  }
> > +
> > +void delay(uint64_t cycles)
> > +{
> > +	uint64_t start = get_tb();
> > +	while((get_tb() - start) < cycles)
> > +		cpu_relax();
> Shouldn't there be some kind of wrap-around detection, like you had
> it
> in v2 for the decrementer based sleep function?
Thanks for catching that, highly unlikely this will overflow (64-bit
for timebase vs 31-bit for decrementer) but probably worth adding a
check to be sure.
> 
> > 
> > +}
> > +
> > +void udelay(uint64_t us)
> > +{
> > +	delay((us * tb_hz) / 1000000);
> > +}
> > diff --git a/lib/powerpc/setup.c b/lib/powerpc/setup.c
> > index e3d2afa..e7fa525 100644
> > --- a/lib/powerpc/setup.c
> > +++ b/lib/powerpc/setup.c
> > @@ -24,6 +24,7 @@ extern void setup_args_progname(const char
> > *args);
> >  
> >  u32 cpus[NR_CPUS] = { [0 ... NR_CPUS-1] = (~0U) };
> >  int nr_cpus;
> > +uint64_t tb_hz;
> >  
> >  struct mem_region mem_regions[NR_MEM_REGIONS];
> >  phys_addr_t __physical_start, __physical_end;
> > @@ -51,6 +52,17 @@ static void cpu_set(int fdtnode, u32 regval,
> > void *info)
> >  	}
> >  	cpus[cpu] = regval;
> >  
> > +	/* set timebase frequency */
> > +	if (!tb_hz) {
> > +		const struct fdt_property *prop;
> > +		u32 *data;
> > +		prop = fdt_get_property(dt_fdt(), fdtnode,
> > +					"timebase-frequency",
> > NULL);
> > +		assert(prop != NULL);
> > +		data = (u32 *)prop->data;
> > +		tb_hz = fdt32_to_cpu(*data);
> You could short-cut that to fdt32_to_cpu(*(u32 *)prop->data) and get
> rid
> of the "data" variable.
Moved this into the code block below were those are both already
defined.
> 
> > 
> > +	}
> > +
> >  	/* set exception stack address for this CPU (in SPGR0) */
> >  
> >  	asm volatile ("mtsprg0 %[addr]" ::
> > 
>  Thomas
>