Re: [PATCH 3/7] thermal/drivers/core: Add init section table for self-encapsulation

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

Hi, Daniel,

thanks for clarifying.
It is true that we need to make thermal framework ready as early as
possible. And a static table works for me as long as vmlinux.lds.h is
the proper place.

Arnd,
are you okay with this patch? if yes, I suppose I can take it through
my tree, right?

thanks,
rui

On 一, 2019-04-22 at 14:11 +0200, Daniel Lezcano wrote:
> Hi Zhang,
> 
> 
> On 22/04/2019 10:43, Zhang Rui wrote:
> > 
> > Hi, Daniel,
> > 
> > Thanks for the patches, it looks good to me except this one and
> > patch
> > 4/7.
> > 
> > First, I don't think this is a cyclic dependency issue as they are
> > in
> > the same module.
> The governors have to export their [un]register functions in order to
> have the core to use them.
> 
> The core has to export the [un]register function in order to have the
> governors to use them.
> 
> From my point of view it is a cyclic dependency. In any other
> subsystems, the plugins/governor/drivers/whatever don't have to
> export
> their functions to the core, they use the core's exported functions.
> 
> > 
> > Second, I have not read include/asm-generic/vmlinux.lds.h before,
> > it
> > seems that it is used for architecture specific stuff. Fix a
> > thermal
> > issue in this way seems overkill to me.
> It is not architecture specific, it belongs to asm-generic. All init
> calls are defined in it and more. It is a common way to define static
> tables from different files without adding dependency and unload it
> after init.
> 
> All clk, timers, acpi tables, irq chip, cpuidle and cpu methods are
> defined this way.
> 
> When the thermal_core.c uses at the end fs_initcall it uses the same
> mechanism.
> 
> 
> > 
> > IMO, to make the code clean, we can build the governors as separate
> > modules just like we do for cpu governors.
> > This brings to the old commit 80a26a5c22b9("Thermal: build thermal
> > governors into thermal_sys module"), and that was introduced to fix
> > a
> > problem when CONFIG_THERMAL is set to 'm'. So I think we can switch
> > back to the old way as the problem is gone now.
> > 
> > what do you think?
> IMO, having the governors built as module is not a good thing because
> the SoC needs the governor to be ready as soon as possible at boot
> time.
> I've been told some boards reboot at boot time because the governor
> comes too late with the userspace governor for example.
> 
> If you don't like the vmlinuz.lds.h approch (but again it is a common
> way to initialize table and I wrote it to extend to more thermal
> table
> in the future) we can change the thermal core to replace
> fs_initcall()
> by core_initcall() and use postcore_initcall() in the governor.
> 
> 
> 
> > 
> > Patch 1,2,5,6,7 applied first.
> > 
> > thanks,
> > rui
> > 
> > On 二, 2019-04-02 at 18:12 +0200, Daniel Lezcano wrote:
> > > 
> > > Currently the governors are declared in their respective files
> > > but
> > > they
> > > export their [un]register functions which in turn call the
> > > [un]register
> > > the governors core's functions. That implies a cyclic dependency
> > > which is
> > > not desirable. There is a way to self-encapsulate the governors
> > > by
> > > letting
> > > them to declare themselves in a __init section table.
> > > 
> > > Define the table in the asm generic linker description like the
> > > other
> > > tables and provide the specific macros to deal with.
> > > 
> > > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> > > ---
> > >  drivers/thermal/thermal_core.h    | 16 ++++++++++++++++
> > >  include/asm-generic/vmlinux.lds.h | 11 +++++++++++
> > >  2 files changed, 27 insertions(+)
> > > 
> > > diff --git a/drivers/thermal/thermal_core.h
> > > b/drivers/thermal/thermal_core.h
> > > index 0df190ed82a7..28d18083e969 100644
> > > --- a/drivers/thermal/thermal_core.h
> > > +++ b/drivers/thermal/thermal_core.h
> > > @@ -15,6 +15,22 @@
> > >  /* Initial state of a cooling device during binding */
> > >  #define THERMAL_NO_TARGET -1UL
> > >  
> > > +/* Init section thermal table */
> > > +extern struct thermal_governor * __governor_thermal_table[];
> > > +extern struct thermal_governor * __governor_thermal_table_end[];
> > > +
> > > +#define THERMAL_TABLE_ENTRY(table, name)			
> > > \
> > > +        static typeof(name) * __thermal_table_entry_##name	
> > > \
> > > +	__used __section(__##table##_thermal_table)		
> > > \
> > > +		= &name;
> > > +
> > > +#define THERMAL_GOVERNOR_DECLARE(name)	THERMAL_TABLE_ENTR
> > > Y(go
> > > vernor, name)
> > > +
> > > +#define for_each_governor_table(__governor)		\
> > > +	for (__governor = __governor_thermal_table;	\
> > > +	     __governor < __governor_thermal_table_end;	\
> > > +	     __governor++)
> > > +
> > >  /*
> > >   * This structure is used to describe the behavior of
> > >   * a certain cooling device on a certain trip point
> > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-
> > > generic/vmlinux.lds.h
> > > index f8f6f04c4453..9893a3ed242a 100644
> > > --- a/include/asm-generic/vmlinux.lds.h
> > > +++ b/include/asm-generic/vmlinux.lds.h
> > > @@ -239,6 +239,16 @@
> > >  #define ACPI_PROBE_TABLE(name)
> > >  #endif
> > >  
> > > +#ifdef CONFIG_THERMAL
> > > +#define THERMAL_TABLE(name)					
> > > 	
> > > \
> > > +        . = ALIGN(8);						
> > > 	\
> > > +        __##name##_thermal_table = .;				
> > > 	\
> > > +        KEEP(*(__##name##_thermal_table))			
> > > 	
> > > \
> > > +        __##name##_thermal_table_end = .;
> > > +#else
> > > +#define THERMAL_TABLE(name)
> > > +#endif
> > > +
> > >  #define KERNEL_DTB()						
> > > 	
> > > \
> > >  	STRUCT_ALIGN();						
> > > 	\
> > >  	__dtb_start = .;						
> > > \
> > > @@ -609,6 +619,7 @@
> > >  	IRQCHIP_OF_MATCH_TABLE()					
> > > \
> > >  	ACPI_PROBE_TABLE(irqchip)				
> > > 	
> > > \
> > >  	ACPI_PROBE_TABLE(timer)					
> > > 	\
> > > +	THERMAL_TABLE(governor)					
> > > 	\
> > >  	EARLYCON_TABLE()						
> > > \
> > >  	LSM_TABLE()
> > >  
>