linux-kernel - Re: [alsa-devel] [Patch v6 1/7] slimbus: Device management on SLIMbus

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Message-ID: <c777820e-fd60-f8d1-4fc1-5934ff18af1b@linaro.org>
Date:   Wed, 11 Oct 2017 10:42:23 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     gregkh@...uxfoundation.org, broonie@...nel.org,
        alsa-devel@...a-project.org, mark.rutland@....com,
        michael.opdenacker@...e-electrons.com, poeschel@...onage.de,
        andreas.noever@...il.com, gong.chen@...ux.intel.com, arnd@...db.de,
        kheitke@...ience.com, bp@...e.de, devicetree@...r.kernel.org,
        james.hogan@...tec.com, pawel.moll@....com,
        linux-arm-msm@...r.kernel.org, sharon.dvir1@...l.huji.ac.il,
        robh+dt@...nel.org, sdharia@...eaurora.org, alan@...ux.intel.com,
        treding@...dia.com, mathieu.poirier@...aro.org, jkosina@...e.cz,
        linux-kernel@...r.kernel.org, daniel@...ll.ch, joe@...ches.com,
        davem@...emloft.net
Subject: Re: [alsa-devel] [Patch v6 1/7] slimbus: Device management on SLIMbus



On 11/10/17 05:07, Vinod Koul wrote:
> On Tue, Oct 10, 2017 at 06:21:34PM +0100, Srinivas Kandagatla wrote:
>> On 10/10/17 17:49, Vinod Koul wrote:
> 
>>>>>> +static int slim_device_probe(struct device *dev)
>>>>>> +{
>>>>>> +	struct slim_device	*sbdev;
>>>>>> +	struct slim_driver	*sbdrv;
>>>>>> +	int status = 0;
>>>>>> +
>>>>>> +	sbdev = to_slim_device(dev);
>>>>>> +	sbdrv = to_slim_driver(dev->driver);
>>>>>> +
>>>>>> +	sbdev->driver = sbdrv;
>>>>>> +
>>>>>> +	if (sbdrv->probe)
>>>>>> +		status = sbdrv->probe(sbdev);
>>>>>> +
>>>>>> +	if (status)
>>>>>> +		sbdev->driver = NULL;
>>>>>> +	else if (sbdrv->device_up)
>>>>>> +		schedule_slim_report(sbdev->ctrl, sbdev, true);
>>>>>
>>>>> can you please explain what this is trying to do?
>>>>
>>>> It is scheduling a device_up() callback in workqueue for reporting
>>>> discovered device.
>>>
>>> any reason for that? Would the device not announce itself on the bus and
>>> then you can synchronously update the device.
>> You are correct,  Device should announce itself in all cases. core should
>> only call this callback only when device is announced, it does not make
>> sense for this call in slim_device_probe(). Will remove it from here in next
>> version.
> 
> Okay great. Btw do you need a notify being scheduled in those cases? I guess
> your controller would get an interrupt and you will handle that in bottom
> half and then cll this, so why not call in the bottom half?
> 
That makes sense, I will optimize this path, It looks like there are 2 
workqueues in this path. We should be able to get rid of one work-queue.



>>>>>> +/**
>>>>>> + * slim_register_controller: Controller bring-up and registration.
>> ...
>>>>>> +
>>>>>> +	mutex_init(&ctrl->m_ctrl);
>>>>>> +	ret = device_register(&ctrl->dev);
>>>>>
>>>>> one more device_register?? Can you explain why
>>>>>
>>>>
>>>> This is a device for each controller.
>>>
>>> wont the controller have its own platform_device?
>>
>> Reason could be that slim_register controller can be called from any code
>> not just platform devices..
> 
> ah which cases would those be. I was expecting that you would have a
> platform_device as a slimbus controller which would call slim_register?
As of now there is only one controller which uses platform driver, but 
in future there might be more, but this is something which makes the 
slimbus core more flexible.


>