diff mbox series

[v4,16/20] arch_topology: Drop unnecessary check for uninitialised package_id

Message ID 20220621192034.3332546-17-sudeep.holla@arm.com (mailing list archive)
State New, archived
Headers show
Series arch_topology: Updates to add socket support and fix cluster ids | expand

Commit Message

Sudeep Holla June 21, 2022, 7:20 p.m. UTC
With the support of socket node parsing from the device tree and
assigning 0 as package_id in absence of socket nodes, there is no need
to check for invalid package_id. It is always initialised to 0 or values
from the device tree socket nodes.

Just drop that now redundant check for uninitialised package_id.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 drivers/base/arch_topology.c | 11 -----------
 1 file changed, 11 deletions(-)

Comments

Ionela Voinescu June 27, 2022, 1:12 p.m. UTC | #1
On Tuesday 21 Jun 2022 at 20:20:30 (+0100), Sudeep Holla wrote:
> With the support of socket node parsing from the device tree and
> assigning 0 as package_id in absence of socket nodes, there is no need
> to check for invalid package_id. It is always initialised to 0 or values
> from the device tree socket nodes.
> 
> Just drop that now redundant check for uninitialised package_id.
> 
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/base/arch_topology.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 46fa1b70b02b..42448a5a9412 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -611,7 +611,6 @@ static int __init parse_dt_topology(void)
>  {
>  	struct device_node *cn, *map;
>  	int ret = 0;
> -	int cpu;
>  
>  	cn = of_find_node_by_path("/cpus");
>  	if (!cn) {
> @@ -633,16 +632,6 @@ static int __init parse_dt_topology(void)
>  
>  	topology_normalize_cpu_scale();
>  
> -	/*
> -	 * Check that all cores are in the topology; the SMP code will
> -	 * only mark cores described in the DT as possible.
> -	 */
> -	for_each_possible_cpu(cpu)
> -		if (cpu_topology[cpu].package_id < 0) {
> -			ret = -EINVAL;
> -			break;
> -		}
> -

Maybe it would still be good to keep this for systems with potential
errors in DT, where one forgets to add a core in cpu-map.

For example, if I modify juno.dts as follows:

--- a/arch/arm64/boot/dts/arm/juno.dts
+++ b/arch/arm64/boot/dts/arm/juno.dts
@@ -51,12 +51,9 @@ core0 {
                                        cpu = <&A53_0>;
                                };
                                core1 {
-                                       cpu = <&A53_1>;
-                               };
-                               core2 {
                                        cpu = <&A53_2>;
                                };
-                               core3 {
+                               core2 {
                                        cpu = <&A53_3>;
                                };
                        };

and miss a little core in cluster1, I would end up with an incomplete
topology: core3 would have cluster_id as -1, while all other CPUs would
have a valid value; also, core3 would have package_id = -1.

Thanks,
Ionela.

>  out_map:
>  	of_node_put(map);
>  out:
> -- 
> 2.36.1
>
Sudeep Holla June 27, 2022, 4:30 p.m. UTC | #2
On Mon, Jun 27, 2022 at 02:12:52PM +0100, Ionela Voinescu wrote:
> On Tuesday 21 Jun 2022 at 20:20:30 (+0100), Sudeep Holla wrote:
> > With the support of socket node parsing from the device tree and
> > assigning 0 as package_id in absence of socket nodes, there is no need
> > to check for invalid package_id. It is always initialised to 0 or values
> > from the device tree socket nodes.
> > 
> > Just drop that now redundant check for uninitialised package_id.
> > 
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > ---
> >  drivers/base/arch_topology.c | 11 -----------
> >  1 file changed, 11 deletions(-)
> > 
> > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> > index 46fa1b70b02b..42448a5a9412 100644
> > --- a/drivers/base/arch_topology.c
> > +++ b/drivers/base/arch_topology.c
> > @@ -611,7 +611,6 @@ static int __init parse_dt_topology(void)
> >  {
> >  	struct device_node *cn, *map;
> >  	int ret = 0;
> > -	int cpu;
> >  
> >  	cn = of_find_node_by_path("/cpus");
> >  	if (!cn) {
> > @@ -633,16 +632,6 @@ static int __init parse_dt_topology(void)
> >  
> >  	topology_normalize_cpu_scale();
> >  
> > -	/*
> > -	 * Check that all cores are in the topology; the SMP code will
> > -	 * only mark cores described in the DT as possible.
> > -	 */
> > -	for_each_possible_cpu(cpu)
> > -		if (cpu_topology[cpu].package_id < 0) {
> > -			ret = -EINVAL;
> > -			break;
> > -		}
> > -
> 
> Maybe it would still be good to keep this for systems with potential
> errors in DT, where one forgets to add a core in cpu-map.
>

Though I would ideally prefer to catch such DT issues with schema, I know
we are no there yet. So I agree to retain this.

> For example, if I modify juno.dts as follows:
> 
> --- a/arch/arm64/boot/dts/arm/juno.dts
> +++ b/arch/arm64/boot/dts/arm/juno.dts
> @@ -51,12 +51,9 @@ core0 {
>                                         cpu = <&A53_0>;
>                                 };
>                                 core1 {
> -                                       cpu = <&A53_1>;
> -                               };
> -                               core2 {
>                                         cpu = <&A53_2>;
>                                 };
> -                               core3 {
> +                               core2 {
>                                         cpu = <&A53_3>;
>                                 };
>                         };
> 
> and miss a little core in cluster1, I would end up with an incomplete
> topology: core3 would have cluster_id as -1, while all other CPUs would
> have a valid value; also, core3 would have package_id = -1.
> 

Indeed. I didn't consider the case where DT would have issues when I dropped
this check. I will drop this patch. Thanks again.
diff mbox series

Patch

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 46fa1b70b02b..42448a5a9412 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -611,7 +611,6 @@  static int __init parse_dt_topology(void)
 {
 	struct device_node *cn, *map;
 	int ret = 0;
-	int cpu;
 
 	cn = of_find_node_by_path("/cpus");
 	if (!cn) {
@@ -633,16 +632,6 @@  static int __init parse_dt_topology(void)
 
 	topology_normalize_cpu_scale();
 
-	/*
-	 * Check that all cores are in the topology; the SMP code will
-	 * only mark cores described in the DT as possible.
-	 */
-	for_each_possible_cpu(cpu)
-		if (cpu_topology[cpu].package_id < 0) {
-			ret = -EINVAL;
-			break;
-		}
-
 out_map:
 	of_node_put(map);
 out: