Re: [PATCH v8 08/21] dt / chosen: Add linux,uefi-stub-generated-dtb property

[Graeme Gregory]

On Mon, Feb 02, 2015 at 01:40:33PM +0000, Leif Lindholm wrote:
> On Mon, Feb 02, 2015 at 08:45:36PM +0800, Hanjun Guo wrote:
> > When system supporting both DT and ACPI but firmware providing
> > no dtb, we can use this linux,uefi-stub-generated-dtb property
> > to let kernel know that we can try ACPI configuration data even
> > if no "acpi=force" is passed in early parameters.
> > 
> > CC: Mark Rutland <mark.rutland@xxxxxxx>
> > CC: Jonathan Corbet <corbet@xxxxxxx>
> > CC: Catalin Marinas <catalin.marinas@xxxxxxx>
> > CC: Will Deacon <will.deacon@xxxxxxx>
> > CC: Leif Lindholm <leif.lindholm@xxxxxxxxxx>
> > CC: Grant Likely <grant.likely@xxxxxxxxxx>
> > CC: Matt Fleming <matt.fleming@xxxxxxxxx>
> > Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> > ---
> >  Documentation/arm/uefi.txt         |  3 +++
> >  arch/arm64/include/asm/acpi.h      |  1 +
> >  arch/arm64/kernel/setup.c          | 30 ++++++++++++++++++++++++++++++
> >  drivers/firmware/efi/libstub/fdt.c |  8 ++++++++
> >  4 files changed, 42 insertions(+)
> > 
> > diff --git a/Documentation/arm/uefi.txt b/Documentation/arm/uefi.txt
> > index d60030a..5f86eae 100644
> > --- a/Documentation/arm/uefi.txt
> > +++ b/Documentation/arm/uefi.txt
> > @@ -60,5 +60,8 @@ linux,uefi-mmap-desc-ver  | 32-bit | Version of the mmap descriptor format.
> >  --------------------------------------------------------------------------------
> >  linux,uefi-stub-kern-ver  | string | Copy of linux_banner from build.
> >  --------------------------------------------------------------------------------
> > +linux,uefi-stub-generated-dtb  | bool | Indication for no DTB provided by
> > +			       |      | firmware.
> > +--------------------------------------------------------------------------------
> 
> Apologies for the late bikeshedding, but the discussion on this topic
> previsously was lively enough that I thought I'd let it die down a bit
> before seeing if I had anything to add.
> 
> That, and I just realised something:
> One alternative to this added DT entry is that we could treat the
> absence of a registered UEFI configuration table as the indication
> that no HW description was provided from firmware, since the stub does
> not call InstallConfigurationTable() on the DT it generates. This does
> move the ability to detect to after efi_init(), but this should be
> fine for ACPI-purposes.
> 
That would not work as expected in the kexec/Xen use case though as they
may genuinely boot with DT from an ACPI host without UEFI.

> If that is deemed undesirable, I would still prefer Catalin's
> suggested name ("linux,bare-dtb"), which describes the state rather
> than the route we took to get there.
> 
I agree.

Graeme

> >  For verbose debug messages, specify 'uefi_debug' on the kernel command line.
> > diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> > index 496c33b..9fcf632 100644
> > --- a/arch/arm64/include/asm/acpi.h
> > +++ b/arch/arm64/include/asm/acpi.h
> > @@ -49,6 +49,7 @@ static inline void arch_fix_phys_package_id(int num, u32 slot) { }
> >  
> >  #else
> >  static inline void disable_acpi(void) { }
> > +static inline void enable_acpi(void) { }
> >  #endif /* CONFIG_ACPI */
> >  
> >  #endif /*_ASM_ACPI_H*/
> > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> > index fc4fb7b..510a681 100644
> > --- a/arch/arm64/kernel/setup.c
> > +++ b/arch/arm64/kernel/setup.c
> > @@ -371,6 +371,29 @@ static void __init request_standard_resources(void)
> >  	}
> >  }
> >  
> > +static int __init dt_scan_chosen(unsigned long node, const char *uname,
> > +			int depth, void *data)
> > +{
> > +	const char *p;
> > +
> > +	if (depth != 1 || !data || (strcmp(uname, "chosen") != 0))
> > +		return 0;
> > +
> > +	p = of_get_flat_dt_prop(node, "linux,uefi-stub-generated-dtb", NULL);
> > +	*(bool *)data = p ? true : false;
> > +
> > +	return 1;
> > +}
> > +
> > +static bool __init is_uefi_stub_generated_dtb(void)
> > +{
> > +	bool flag = false;
> > +
> > +	of_scan_flat_dt(dt_scan_chosen, &flag);
> > +
> > +	return flag;
> > +}
> > +
> >  u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
> >  
> >  void __init setup_arch(char **cmdline_p)
> > @@ -399,6 +422,13 @@ void __init setup_arch(char **cmdline_p)
> >  	parse_early_param();
> >  
> >  	/*
> > +	 * If no dtb provided by firmware, enable ACPI and give system a
> > +	 * chance to boot with ACPI configuration data
> > +	 */
> > +	if (is_uefi_stub_generated_dtb() && acpi_disabled)
> > +		enable_acpi();
> > +
> > +	/*
> >  	 *  Unmask asynchronous aborts after bringing up possible earlycon.
> >  	 * (Report possible System Errors once we can report this occurred)
> >  	 */
> > diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
> > index c846a96..3777d50 100644
> > --- a/drivers/firmware/efi/libstub/fdt.c
> > +++ b/drivers/firmware/efi/libstub/fdt.c
> > @@ -154,6 +154,14 @@ efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
> >  	if (status)
> >  		goto fdt_set_fail;
> >  
> > +	/* Add a property to show the dtb is generated by uefi stub */
> > +	if (!orig_fdt) {
> > +		status = fdt_setprop(fdt, node,
> > +				     "linux,uefi-stub-generated-dtb", NULL, 0);
> > +		if (status)
> > +			goto fdt_set_fail;
> > +	}
> > +
> >  	return EFI_SUCCESS;
> >  
> >  fdt_set_fail:
> > -- 
> > 1.9.1
> > 
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