Re: [PATCH RFC v2 07/10] arm_mpam: Fix mpam_dt_create_foundling_msc() to create MSC platform devices

[Yin Li]

On 9/14/2026 5:37 PM, Yin Li wrote:
> The original code created a platform device for the cache node itself
> rather than for the MSC, so the MSC was never created. Instead, walk
> the cache's children using for_each_child_of_node_scoped() and create
> the platform device for the MSC child node, skipping cache parents
> that firmware has marked disabled.
>
> Co-developed-by: Huang Yiwei <huang.yiwei@xxxxxxxxxxxxxxxx>
> Signed-off-by: Huang Yiwei <huang.yiwei@xxxxxxxxxxxxxxxx>
> Signed-off-by: Yin Li <yin.li@xxxxxxxxxxxxxxxx>
> ---
>   drivers/resctrl/mpam_devices.c | 27 ++++++++++++---------------
>   1 file changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 480e38cfa86d..7ef3ed55b066 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -2366,23 +2366,20 @@ static struct platform_driver mpam_msc_driver = {
>    */
>   static void mpam_dt_create_foundling_msc(void)
>   {
> -	struct platform_device *pdev;
> -	struct device_node *cache;
> -
> -	for_each_compatible_node(cache, NULL, "cache") {
> -		struct device_node *cache_device;
> -
> -		if (of_node_check_flag(cache, OF_POPULATED))
> -			continue;
> -
> -		cache_device = of_find_matching_node_and_match(cache, mpam_of_match, NULL);
> -		if (!cache_device)
> +	for_each_compatible_node_scoped(cache, NULL, "cache") {
> +		if (!of_device_is_available(cache))
>   			continue;

Hi,

As sashiko-bot said：Checking of_device_is_available(cache) here 
introduces a mismatch with mpam_dt_count_msc(), which only checks 
whether the MSC node itself is available, not its parent cache. And in 
practice, cache nodes are rarely if ever marked as disabled in the 
device tree, so this check adds unnecessary inconsistency without a real 
benefit.

I'll remove the cache availability check in the next version to keep the 
two consistent.

Thanks,
Yin


> -		of_node_put(cache_device);
>   
> -		pdev = of_platform_device_create(cache, "cache", NULL);
> -		if (!pdev)
> -			pr_err_once("Failed to create MSC devices under caches\n");
> +		for_each_child_of_node_scoped(cache, child) {
> +			if (!of_match_node(mpam_of_match, child))
> +				continue;
> +			if (!of_device_is_available(child))
> +				continue;
> +			if (of_node_check_flag(child, OF_POPULATED))
> +				continue;
> +			if (!of_platform_device_create(child, NULL, NULL))
> +				pr_err("Failed to create MSC device for %pOF\n", child);
> +		}
>   	}
>   }
>   

--
Thx and BRs,
Yin