Re: [PATCH v2 09/18] firmware: arm_scmi: probe and initialise all the supported protocols

[Julien Thierry <julien.thierry@arm.com>]

On 06/09/17 14:31, Sudeep Holla wrote:
> 
> 
> On 06/09/17 10:41, Julien Thierry wrote:
>>
>>
>> On 04/08/17 15:31, Sudeep Holla wrote:
>>> Now that we have basic support for all the protocols in the
>>> specification, let's probe them individually and initialise them.
>>>
>>> Cc: Arnd Bergmann <arnd@arndb.de>
>>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>>> ---
>>>    drivers/firmware/arm_scmi/common.h |  5 +++
>>>    drivers/firmware/arm_scmi/driver.c | 80
>>> +++++++++++++++++++++++++++++++++++++-
>>>    2 files changed, 84 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/firmware/arm_scmi/common.h
>>> b/drivers/firmware/arm_scmi/common.h
>>> index 7473dfcad4ee..d7c73a8d260b 100644
>>> --- a/drivers/firmware/arm_scmi/common.h
>>> +++ b/drivers/firmware/arm_scmi/common.h
>>> @@ -118,4 +118,9 @@ int scmi_version_get(const struct scmi_handle *h,
>>> u8 protocol, u32 *version);
>>>    void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
>>>                         u8 *prot_imp);
>>>    +typedef int (*scmi_init_fn_t)(struct scmi_handle *);
>>>    int scmi_base_protocol_init(struct scmi_handle *h);
>>> +int scmi_perf_protocol_init(struct scmi_handle *h);
>>> +int scmi_sensors_protocol_init(struct scmi_handle *h);
>>> +int scmi_power_protocol_init(struct scmi_handle *h);
>>> +int scmi_clock_protocol_init(struct scmi_handle *h);
>>> diff --git a/drivers/firmware/arm_scmi/driver.c
>>> b/drivers/firmware/arm_scmi/driver.c
>>> index 601d0d7210d9..6f31761043e2 100644
>>> --- a/drivers/firmware/arm_scmi/driver.c
>>> +++ b/drivers/firmware/arm_scmi/driver.c
>>> @@ -157,6 +157,12 @@ struct scmi_shared_mem {
>>>        u8 msg_payload[0];
>>>    };
>>>    +struct scmi_protocol_match {
>>> +    u8 protocol_id;
>>> +    scmi_init_fn_t fn;
>>
>> Could we call this "init" or "prot_init"?
>>
> 
> Done
> 
>>> +    char name[32];
>>> +};
>>> +
>>>    static int scmi_linux_errmap[] = {
>>>        /* better than switch case as long as return value is continuous */
>>>        0,            /* SCMI_SUCCESS */
>>> @@ -687,6 +693,41 @@ static int scmi_xfer_info_init(struct scmi_info
>>> *sinfo)
>>>        return 0;
>>>    }
>>>    +static const struct scmi_protocol_match scmi_protocols[] = {
>>> +    {
>>> +        .protocol_id = SCMI_PROTOCOL_PERF,
>>> +        .fn = scmi_perf_protocol_init,
>>> +        .name = "scmi-cpufreq",
>>> +    }, {
>>> +        .protocol_id = SCMI_PROTOCOL_CLOCK,
>>> +        .fn = scmi_clock_protocol_init,
>>> +        .name = "scmi-clocks",
>>> +    }, {
>>> +        .protocol_id = SCMI_PROTOCOL_POWER,
>>> +        .fn = scmi_power_protocol_init,
>>> +        .name = "scmi-power-domain",
>>> +    }, {
>>> +        .protocol_id = SCMI_PROTOCOL_SENSOR,
>>> +        .fn = scmi_sensors_protocol_init,
>>> +        .name = "scmi-hwmon",
>>> +    },
>>> +    {}
>>> +};
>>> +
>>> +static const struct scmi_protocol_match *scmi_protocol_match_get(u8
>>> protocol_id)
>>> +{
>>> +    int i;
>>> +    const struct scmi_protocol_match *match = NULL, *loop =
>>> scmi_protocols;
>>> +
>>> +    for (i = 0; i < ARRAY_SIZE(scmi_protocols); i++, loop++)
>>> +        if (loop->protocol_id == protocol_id) {
>>> +            match = loop;
>>> +            break;
>>> +        }
>>> +
>>> +    return match;
>>> +}
>>> +
>>
>> The "match" variable is not needed. We can just return "loop" in the if
>> branch and return NULL at the end of the function. Unless we are
>> following some coding standard that advises against that?
>>
> 
> Agreed and fixed locally.
> 
>>>    static int scmi_mailbox_check(struct device_node *np)
>>>    {
>>>        struct of_phandle_args arg;
>>> @@ -778,7 +819,7 @@ static int scmi_probe(struct platform_device *pdev)
>>>        const struct scmi_desc *desc;
>>>        struct scmi_info *info;
>>>        struct device *dev = &pdev->dev;
>>> -    struct device_node *np = dev->of_node;
>>> +    struct device_node *child, *np = dev->of_node;
>>>          /* Only mailbox method supported, check for the presence of
>>> one */
>>>        if (scmi_mailbox_check(np)) {
>>> @@ -817,6 +858,43 @@ static int scmi_probe(struct platform_device *pdev)
>>>            return ret;
>>>        }
>>>    +    for_each_available_child_of_node(np, child) {
>>> +        int init_ret;
>>> +        u32 prot_id;
>>> +        const struct scmi_protocol_match *match;
>>> +
>>> +        if (of_property_read_u32(child, "reg", &prot_id))
>>> +            continue;
>>> +
>>> +        prot_id &= MSG_PROTOCOL_ID_MASK;
>>> +
>>> +        if (!scmi_is_protocol_implemented(handle, prot_id)) {
>>> +            dev_err(dev, "SCMI protocol %d not implemented\n",
>>> +                prot_id);
>>> +            continue;
>>> +        }
>>> +
>>> +        match = scmi_protocol_match_get(prot_id);
>>> +        if (match) {
>>> +            struct platform_device *cdev;
>>> +
>>> +            cdev = of_platform_device_create(child, match->name,
>>> +                             dev);
>>> +            if (!cdev) {
>>> +                dev_err(dev, "failed to create %s device\n",
>>> +                    match->name);
>>> +                continue;
>>> +            }
>>> +
>>> +            init_ret = match->fn(handle);
>>> +            if (init_ret) {
>>> +                dev_err(dev, "SCMI protocol %d init error %d\n",
>>> +                    prot_id, init_ret);
>>> +                of_platform_device_destroy(&cdev->dev, NULL);
>>> +            }
>>> +        }
>>> +    }
>>> +
>>
>> For the code in the "if (match)" branch, would it be better to have an
>> inline function "scmi_create_protocol_device" or something with a name
>> that fits?
>>
> 
> Done
> 
>> Also I was wondering, what is the difference between the protocol being
>> implemented and finding the matching structure? Feels like there is a
>> bit of redundancy. If the protocol is implemented but doesn't have a
>> match structure does it just mean it doesn't need any specific
>> initialization?
>>
> 
> Yes, that's the idea. One reason to have both check is backward
> compatibility. Suppose new protocols are implemented in the f/w but DT
> doesn't have them or know how to use it or there are no users of that
> feature, then skip initializing it. Similarly if DT is updated but not
> the firmware.
> 

Oh I see, makes sense. Thanks for explaining.

Cheers,

-- 
Julien Thierry