Updating the define_machine() structure at runtime?

Updating the define_machine() structure at runtime?

[Timur Tabi]

I would like to get some opinions on the following.

I'm working on extending our existing board definition files to support our
ePAPR reference hypervisor.  Because our hypervisor provides a virtual PIC, we
need to have different functions for define_machine() structure that related to
the PIC, but most everything else can stay the same.

define_machine(p4080_hv) {
	.name			= "P4080DS HV",
	.probe			= p4080hv_probe,
	.setup_arch		= corenet_ds_setup_arch,
	.init_IRQ		= fsl_hv_pic_init,
#ifdef CONFIG_PCI
	.pcibios_fixup_bus	= fsl_pcibios_fixup_bus,
#endif
	.get_irq		= ehv_pic_get_irq,
	.restart		= fsl_hv_restart,
	.power_off		= fsl_hv_halt,
	.halt			= fsl_hv_halt,
	.calibrate_decr		= generic_calibrate_decr,
	.progress		= udbg_progress,
};

Rather than create two such structures for each board that can support the
hypervisor (one with HV support, one without), I would like to do the following
instead.  What do you all think?

define_machine(p4080_ds) {
	.name			= "P4080 DS",
	.probe			= p4080_ds_probe,
	...
	.get_irq		= mpic_get_coreint_irq,
};

static int __init p4080_ds_probe(void)
{
	...
#ifdef CONFIG_FSL_HYPERVISOR
	if (of_flat_dt_is_compatible(root, "fsl,P4080DS-hv")) {
		mach_p4080_ds.get_irq = ehv_pic_get_irq;
		...
		return 1;
	} else
		return 0;
#endif	


-- 
Timur Tabi
Linux kernel developer at Freescale

Re: Updating the define_machine() structure at runtime?

[Benjamin Herrenschmidt]

On Mon, 2011-05-16 at 11:21 -0500, Timur Tabi wrote:
> I would like to get some opinions on the following.
> 
> I'm working on extending our existing board definition files to support our
> ePAPR reference hypervisor.  Because our hypervisor provides a virtual PIC, we
> need to have different functions for define_machine() structure that related to
> the PIC, but most everything else can stay the same.

 .../...

> static int __init p4080_ds_probe(void)
> {
> 	...
> #ifdef CONFIG_FSL_HYPERVISOR
> 	if (of_flat_dt_is_compatible(root, "fsl,P4080DS-hv")) {
> 		mach_p4080_ds.get_irq = ehv_pic_get_irq;
> 		...
> 		return 1;
> 	} else
> 		return 0;
> #endif	

One approach i've been taking more often nowadays is to have the PIC
code setup the ppc_md hooks itself.

You don't need to do it in probe(), just in setup_arch or init_IRQ,
wherever you do your PIC discovery, have it set it up.

For example, xics sets get_irq itself, which is necessary because the
xics code itself can have multiple variants.

We could probably make mpic.c do the same when MPIC_PRIMARY is set (or
keep that a wrapper for now).
 
Cheers,
Ben.