Re: [PATCH v1 1/4] driver core: Rely on supplier driver binding at link creation

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi,

On 9/21/26 21:12, alucerop@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
> 
> Differentiate between driver binding from PM dependency when a device
> link is created. Rely on the device being bound to a driver for validating
> the supplier as some device drivers could not support PM.
> 
> Check for supplier's PM state only if consumer specifies PM_RUNTIME flag.

Hmmm this patch seems to have broken pretty much all the boards I'm running that
boot with DT. I'm getting logs such as :

platform 16100000.serial: Failed to create device link (0x124) with supplier
  16000400.clock-controller

Some are just hanging at "Starting kernel..." from u-boot.

Then boards go silent as the uart dies, and I'm using that uart to access the
device's console :(

Found with a WIP stmmac runner for netdev CI.

Unfortunately I don't have much logs to share, as this just prevents the boards
from booting :( With this patch reverted, all boards boot fine

Maxime

> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> ---
>  drivers/base/core.c | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 4c0c373998a1..eb6d87e35d76 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -834,15 +834,26 @@ struct device_link *device_link_add(struct device *consumer,
>  	device_pm_lock();
>  
>  	/*
> -	 * If the supplier has not been fully registered yet or there is a
> -	 * reverse (non-SYNC_STATE_ONLY) dependency between the consumer and
> -	 * the supplier already in the graph, return NULL. If the link is a
> -	 * SYNC_STATE_ONLY link, we don't check for reverse dependencies
> -	 * because it only affects sync_state() callbacks.
> +	 * If the supplier has not been fully registered yet with a driver
> +	 * return NULL.
>  	 */
> -	if (!device_pm_initialized(supplier)
> -	    || (!(flags & DL_FLAG_SYNC_STATE_ONLY) &&
> -		  device_is_dependent(consumer, supplier))) {
> +	scoped_guard(device, supplier) {
> +		if (!device_is_bound(supplier)) {
> +			link = NULL;
> +			goto out;
> +		}
> +	}
> +	/*
> +	 * If consumer asks for PM to use the link and the supplier has not
> +	 * PM initialized, or if there is a reverse (non-SYNC_STATE_ONLY)
> +	 * dependency between the consumer and the supplier already in the
> +	 * graph, return NULL. If the link is a SYNC_STATE_ONLY link, we
> +	 * don't check for reverse dependencies because it only affects
> +	 * sync_state() callbacks.
> +	 */
> +	if (((flags & DL_FLAG_PM_RUNTIME) && !device_pm_initialized(supplier)) ||
> +	    (!(flags & DL_FLAG_SYNC_STATE_ONLY) &&
> +	     device_is_dependent(consumer, supplier))) {
>  		link = NULL;
>  		goto out;
>  	}