[RFC] firmware: arm_scmi: Optimize the iteration of scmi_requested_devices

[Peng Fan]

Hi Dan,

> Subject: Re: [RFC] firmware: arm_scmi: Optimize the iteration of
> scmi_requested_devices
> 
> On Mon, Jan 06, 2025 at 02:57:24PM +0800, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan at nxp.com>
> >
> > scmi_requested_devices is organized in IDR based link lists, so only
> > need to search the link lists when there is a match protocol_id.
> >
> > Back to search the next id with 'continue' to save cpu cycles, if
> > protocol_id does not match.
> >
> > Signed-off-by: Peng Fan <peng.fan at nxp.com>
> > ---
> >
> > RFC:
> >  Tested on i.MX95.
> >
> >  drivers/firmware/arm_scmi/bus.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/firmware/arm_scmi/bus.c
> > b/drivers/firmware/arm_scmi/bus.c index
> 157172a5f2b5..42deab5903fb
> > 100644
> > --- a/drivers/firmware/arm_scmi/bus.c
> > +++ b/drivers/firmware/arm_scmi/bus.c
> > @@ -79,6 +79,8 @@ static int scmi_protocol_device_request(const
> struct scmi_device_id *id_table)
> >  			if (rdev->id_table->protocol_id ==
> >  			    id_table->protocol_id)
> >  				phead = head;
> > +			else
> > +				continue;
> >  		}
> >  		list_for_each_entry(rdev, head, node) {
> >  			if (!strcmp(rdev->id_table->name, id_table-
> >name)) { @@ -89,6
> > +91,7 @@ static int scmi_protocol_device_request(const struct
> scmi_device_id *id_table)
> >  				goto out;
> >  			}
> >  		}
> > +		break;
> >  	}
> 
> I suspect your patch is correct but we could go further.  Removing the
> test for if (!phead) really helps readability.

Thanks. Looks better.

Thanks,
Peng.

> 
> regards,
> dan carpenter
> 
> diff --git a/drivers/firmware/arm_scmi/bus.c
> b/drivers/firmware/arm_scmi/bus.c index
> a3386bf36de5..2c853c84b58f 100644
> --- a/drivers/firmware/arm_scmi/bus.c
> +++ b/drivers/firmware/arm_scmi/bus.c
> @@ -72,14 +72,11 @@ static int scmi_protocol_device_request(const
> struct scmi_device_id *id_table)
>  	 */
>  	mutex_lock(&scmi_requested_devices_mtx);
>  	idr_for_each_entry(&scmi_requested_devices, head, id) {
> -		if (!phead) {
> -			/* A list found registered in the IDR is never
> empty */
> -			rdev = list_first_entry(head, struct
> scmi_requested_dev,
> -						node);
> -			if (rdev->id_table->protocol_id ==
> -			    id_table->protocol_id)
> -				phead = head;
> -		}
> +		/* A list found registered in the IDR is never empty */
> +		rdev = list_first_entry(head, struct
> scmi_requested_dev, node);
> +		if (rdev->id_table->protocol_id != id_table-
> >protocol_id)
> +			continue;
> +
>  		list_for_each_entry(rdev, head, node) {
>  			if (!strcmp(rdev->id_table->name, id_table-
> >name)) {
>  				pr_err("Ignoring duplicate request
> [%d] %s\n", @@ -89,6 +86,8 @@ static int
> scmi_protocol_device_request(const struct scmi_device_id *id_table)
>  				goto out;
>  			}
>  		}
> +		phead = head;
> +		break;
>  	}
> 
>  	/*