Re: [PATCH 03/15] firmware: arm_scmi: Skip protocol initialisation for additional devices

From: Cristian Marussi <cristian.marussi@arm.com>
To: Sudeep Holla <sudeep.holla@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/15] firmware: arm_scmi: Skip protocol initialisation for additional devices
Date: Tue, 10 Dec 2019 18:14:47 +0000	[thread overview]
Message-ID: <944a2d76-a3d3-9238-1960-63c3f29bea05@arm.com> (raw)
In-Reply-To: <20191210145345.11616-4-sudeep.holla@arm.com>

On 10/12/2019 14:53, Sudeep Holla wrote:
> The scmi bus now supports adding multiple devices per protocol,
> and since scmi_protocol_init is called for each scmi device created,
> we must avoid allocating protocol private data and initialising the
> protocol itself if it is already initialised.
> 
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---

Wouldn't be better to add some kind of per-protocol 'initialized' flag somewhere
in the bus abstraction so that the protocol_id itself could be marked as initialized
once bus::scmi_protocol_init() completes successfully so that we could just skip the
invocation itself of bus::scmi_protocol_init() for all the protocols already detected
as initialized ?

Or, if not a flag, maybe deactivating the registered protocol init function itself
once it has been successfully called once .....something along the lines of:

diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index 7a30952b463d..a551a00586c6 100644
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -73,6 +73,8 @@ static int scmi_dev_probe(struct device *dev)
        ret = scmi_protocol_init(scmi_dev->protocol_id, scmi_dev->handle);
        if (ret)
                return ret;
+       idr_replace(&scmi_protocols, dummy_return_0_callback,
+                       scmi_dev->protocol_id);
 
        return scmi_drv->probe(scmi_dev);

[not really tested eh ... :D]

This way we can drop this patch as a whole and avoid any future needs to remember
to add this same sort of logic in the next XYZ protocol implementation.

Cheers

Cristian

>  drivers/firmware/arm_scmi/clock.c   | 3 +++
>  drivers/firmware/arm_scmi/perf.c    | 3 +++
>  drivers/firmware/arm_scmi/power.c   | 3 +++
>  drivers/firmware/arm_scmi/reset.c   | 3 +++
>  drivers/firmware/arm_scmi/sensors.c | 3 +++
>  5 files changed, 15 insertions(+)
> 
> diff --git a/drivers/firmware/arm_scmi/clock.c b/drivers/firmware/arm_scmi/clock.c
> index 32526a793f3a..922b22aaaf84 100644
> --- a/drivers/firmware/arm_scmi/clock.c
> +++ b/drivers/firmware/arm_scmi/clock.c
> @@ -316,6 +316,9 @@ static int scmi_clock_protocol_init(struct scmi_handle *handle)
>  	int clkid, ret;
>  	struct clock_info *cinfo;
> 
> +	if (handle->clk_ops && handle->clk_priv)
> +		return 0; /* initialised already for the first device */
> +
>  	scmi_version_get(handle, SCMI_PROTOCOL_CLOCK, &version);
> 
>  	dev_dbg(handle->dev, "Clock Version %d.%d\n",
> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
> index 601af4edad5e..55c2a4c21ccb 100644
> --- a/drivers/firmware/arm_scmi/perf.c
> +++ b/drivers/firmware/arm_scmi/perf.c
> @@ -710,6 +710,9 @@ static int scmi_perf_protocol_init(struct scmi_handle *handle)
>  	u32 version;
>  	struct scmi_perf_info *pinfo;
> 
> +	if (handle->perf_ops && handle->perf_priv)
> +		return 0; /* initialised already for the first device */
> +
>  	scmi_version_get(handle, SCMI_PROTOCOL_PERF, &version);
> 
>  	dev_dbg(handle->dev, "Performance Version %d.%d\n",
> diff --git a/drivers/firmware/arm_scmi/power.c b/drivers/firmware/arm_scmi/power.c
> index 5abef7079c0a..9a7593238b8f 100644
> --- a/drivers/firmware/arm_scmi/power.c
> +++ b/drivers/firmware/arm_scmi/power.c
> @@ -185,6 +185,9 @@ static int scmi_power_protocol_init(struct scmi_handle *handle)
>  	u32 version;
>  	struct scmi_power_info *pinfo;
> 
> +	if (handle->power_ops && handle->power_priv)
> +		return 0; /* initialised already for the first device */
> +
>  	scmi_version_get(handle, SCMI_PROTOCOL_POWER, &version);
> 
>  	dev_dbg(handle->dev, "Power Version %d.%d\n",
> diff --git a/drivers/firmware/arm_scmi/reset.c b/drivers/firmware/arm_scmi/reset.c
> index ab42c21c5517..809dc8faee1e 100644
> --- a/drivers/firmware/arm_scmi/reset.c
> +++ b/drivers/firmware/arm_scmi/reset.c
> @@ -195,6 +195,9 @@ static int scmi_reset_protocol_init(struct scmi_handle *handle)
>  	u32 version;
>  	struct scmi_reset_info *pinfo;
> 
> +	if (handle->reset_ops && handle->reset_priv)
> +		return 0; /* initialised already for the first device */
> +
>  	scmi_version_get(handle, SCMI_PROTOCOL_RESET, &version);
> 
>  	dev_dbg(handle->dev, "Reset Version %d.%d\n",
> diff --git a/drivers/firmware/arm_scmi/sensors.c b/drivers/firmware/arm_scmi/sensors.c
> index a400ea805fc2..b7f92c37c8a4 100644
> --- a/drivers/firmware/arm_scmi/sensors.c
> +++ b/drivers/firmware/arm_scmi/sensors.c
> @@ -276,6 +276,9 @@ static int scmi_sensors_protocol_init(struct scmi_handle *handle)
>  	u32 version;
>  	struct sensors_info *sinfo;
> 
> +	if (handle->sensor_ops && handle->sensor_priv)
> +		return 0; /* initialised already for the first device */
> +
>  	scmi_version_get(handle, SCMI_PROTOCOL_SENSOR, &version);
> 
>  	dev_dbg(handle->dev, "Sensor Version %d.%d\n",
> --
> 2.17.1
> 

