Re: [PATCH V4 13/23] RISC-V: cpufeature: Add ACPI support in riscv_fill_hwcap()

[Sunil V L]

On Tue, Apr 04, 2023 at 09:57:19PM +0100, Conor Dooley wrote:
> On Tue, Apr 04, 2023 at 11:50:27PM +0530, Sunil V L wrote:
> > On ACPI based systems, the information about the hart
> > like ISA is provided by the RISC-V Hart Capabilities Table (RHCT).
> > Enable filling up hwcap structure based on the information in RHCT.
> > 
> > Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> > ---
> >  arch/riscv/kernel/cpufeature.c | 39 ++++++++++++++++++++++++++++++----
> >  1 file changed, 35 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> > index 63e56ce04162..5d2065b937e5 100644
> > --- a/arch/riscv/kernel/cpufeature.c
> > +++ b/arch/riscv/kernel/cpufeature.c
> > @@ -6,6 +6,7 @@
> >   * Copyright (C) 2017 SiFive
> >   */
> >  
> > +#include <linux/acpi.h>
> >  #include <linux/bitmap.h>
> >  #include <linux/ctype.h>
> >  #include <linux/libfdt.h>
> > @@ -13,6 +14,8 @@
> >  #include <linux/memory.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> > +#include <linux/of_device.h>
> > +#include <asm/acpi.h>
> >  #include <asm/alternative.h>
> >  #include <asm/cacheflush.h>
> >  #include <asm/errata_list.h>
> > @@ -91,6 +94,9 @@ void __init riscv_fill_hwcap(void)
> >  	char print_str[NUM_ALPHA_EXTS + 1];
> >  	int i, j, rc;
> >  	unsigned long isa2hwcap[26] = {0};
> > +	struct acpi_table_header *rhct;
> > +	acpi_status status;
> > +	unsigned int cpu;
> >  
> >  	isa2hwcap['i' - 'a'] = COMPAT_HWCAP_ISA_I;
> >  	isa2hwcap['m' - 'a'] = COMPAT_HWCAP_ISA_M;
> > @@ -103,14 +109,36 @@ void __init riscv_fill_hwcap(void)
> >  
> >  	bitmap_zero(riscv_isa, RISCV_ISA_EXT_MAX);
> >  
> > -	for_each_of_cpu_node(node) {
> > +	if (!acpi_disabled) {
> > +		status = acpi_get_table(ACPI_SIG_RHCT, 0, &rhct);
> > +		if (ACPI_FAILURE(status))
> > +			return;
> > +	}
> > +
> > +	for_each_possible_cpu(cpu) {
> >  		unsigned long this_hwcap = 0;
> >  		DECLARE_BITMAP(this_isa, RISCV_ISA_EXT_MAX);
> >  		const char *temp;
> >  
> > -		if (of_property_read_string(node, "riscv,isa", &isa)) {
> > -			pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
> > -			continue;
> > +		if (acpi_disabled) {
> > +			node = of_cpu_device_node_get(cpu);
> > +			if (node) {
> > +				rc = of_property_read_string(node, "riscv,isa", &isa);
> 
> Hmm, after digging in the previous patch, I think this is actually not
> possible to fail? We already validated it when setting up the mask of
> possible cpus, but I think leaving the error handling here makes things
> a lot more obvious.
> 
Yeah, do you prefer to merge these patches again since only in this
patch, we change the loop to for_each_possible_cpu() from
for_each_of_cpu_node() which actually makes riscv_of_processor_hartid()
not useful?

> I'd swear I gave you a (conditional) R-b on v3 though, no?
> Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> 
Thanks,
Sunil