Date:   Wed, 28 Jun 2017 10:25:40 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Sylwester Nawrocki <snawrocki@...nel.org>,
        Jose Abreu <Jose.Abreu@...opsys.com>
CC:     <linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>
Subject: Re: [PATCH v4 2/4] [media] platform: Add Synopsys Designware HDMI RX
 Controller Driver

Hi Sylwester,


On 27-06-2017 21:34, Sylwester Nawrocki wrote:
> Hi Jose,
>
> On 06/27/2017 10:43 AM, Jose Abreu wrote:
>> On 25-06-2017 22:13, Sylwester Nawrocki wrote:
>>> On 06/20/2017 07:26 PM, Jose Abreu wrote:
>>>> This is an initial submission for the Synopsys Designware HDMI RX
>>>> Controller Driver. This driver interacts with a phy driver so that
>>>> a communication between them is created and a video pipeline is
>>>> configured.
>>>> Signed-off-by: Jose Abreu <joabreu@...opsys.com>
>>>> +static int dw_hdmi_phy_init(struct dw_hdmi_dev *dw_dev)
>>>> +{
>>>> +	struct dw_phy_pdata *phy = &dw_dev->phy_config;
>>>> +	const struct of_device_id *of_id;
>>>> +	struct of_dev_auxdata lookup;
>>> 	struct of_dev_auxdata lookup = { };
>>>
>>> You could initialize to 0 here and...
>>>
>>>> +	struct device_node *child;
>>>> +	const char *drvname;
>>>> +	int ret;
>>>> +
>>>> +	child = dw_hdmi_get_phy_of_node(dw_dev, &of_id);
>>>> +	if (!child || !of_id || !of_id->data) {
>>>> +		dev_err(dw_dev->dev, "no supported phy found in DT\n");
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	drvname = of_id->data;
>>>> +	phy->funcs = &dw_hdmi_phy_funcs;
>>>> +	phy->funcs_arg = dw_dev;
>>>> +
>>>> +	lookup.compatible = (char *)of_id->compatible;
>>>> +	lookup.phys_addr = 0x0;
>>>> +	lookup.name = NULL;
>>> ...drop these two assignments.
>> Ok.
>>
>>>> +	lookup.platform_data = phy;
>>>> +
>>>> +	request_module(drvname);
>>> I'd say this request_module() is not needed when you use the v4l2-async
>>> subnotifiers and the modules are properly installed in the file system.
>>> I might be missing something though.
>> Hmm, well I didn't actually test without request_module but I
>> think its needed, otherwise I would have to do:
>>
>> modprobe phy_module
>> modprobe controller_module
>>
>> With request_module I just have to do:
>>
>> modprobe controller_module
> If you are sure you need it I'm not against that.  But assuming you have udev 
> in your system it should also work like this, without request_module():
>
> 1. modprobe controller_module -> phy device is created in the kernel, uevent sent
> 2. udev receives uevent, finds matching module and does modprobe phy_module
>
> Remaining part is as before: phy_module registers the driver which gets matched with 
> phy device; probe() is called which registers v4l2 subdev which then is registered
> to v4l2_device through the v4l2-async mechanism.
>
> All this assumes udev is running and modules are installed in /lib/modules/$(uname -r).
> E.g. there should be your module alias as shown by modinfo phy_module in
> /lib/modules/$(uname -r)/modules.alias.

The modules are installed but I think I don't have udev :/ I'm
running this on an embedded platform called ARC AXS and I'm using
buildroot with minimal options.

>
>>>> +	ret = of_platform_populate(dw_dev->of_node, NULL, &lookup, dw_dev->dev);
>>>> +	if (ret) {
>>>> +		dev_err(dw_dev->dev, "failed to populate phy driver\n");
>>>> +		return ret;
>>>> +	}
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static void dw_hdmi_phy_exit(struct dw_hdmi_dev *dw_dev)
>>>> +{
>>>> +	of_platform_depopulate(dw_dev->dev);
>>>> +}
>>>> +static int dw_hdmi_v4l2_notify_complete(struct v4l2_async_notifier *notifier)
>>>> +{
>>>> +	struct dw_hdmi_dev *dw_dev = notifier_to_dw_dev(notifier);
>>>> +	int ret;
>>>> +
>>>> +	ret = v4l2_device_register_subdev_nodes(&dw_dev->v4l2_dev);
>>> There shouldn't be multiple struct v4l2_device instances, instead we should
>>> have only one created by the main driver. AFAIU, in your case it would be
>>> driver associated with the dw-hdmi-soc DT node.  And normally such a top level
>>> driver creates subdev device nodes when its all required sub-devices are
>>> available.
>>>
>>> I think this patch could be useful for you:
>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__patchwork.linuxtv.org_patch_41834&d=DwICaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=WHDsc6kcWAl4i96Vm5hJ_19IJiuxx_p_Rzo2g-uHDKw&m=uNHRQkbP_-z8v5d30KFx9pcPEUhlr4ciWY3ZDAVExTA&s=dB9wpgeP7AJg1eDRty0-RKhq3DY-7J5srIzyVoJey5I&e= 
>>>
>>> With that the dw-hdmi-soc driver would have it's v4l2-async notifier's
>>> notify_complete() callback called only when both the hdmi-rx and the
>>> hdmi-phy subdevs are registered.
>> Yeah, I saw the patches. I just implemented this way because they
>> are not merged yet, right?
> I think these patches will be merged in v4.14-rc1, so together with your driver.
> You could apply them locally and indicate that your series depends on them in 
> the cover letter.

Ok, will apply them locally and re-test.

>
>>>> +	if (ret) {
>>>> +		dev_err(dw_dev->dev, "failed to register subdev nodes\n");
>>>> +		return ret;
>>>> +	}
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +static int dw_hdmi_rx_probe(struct platform_device *pdev)
>>>> +{
>>>> +	/* V4L2 initialization */
>>>> +	sd = &dw_dev->sd;
>>>> +	v4l2_subdev_init(sd, &dw_hdmi_sd_ops);
>>>> +	strlcpy(sd->name, dev_name(dev), sizeof(sd->name));
>>>> +	sd->dev = dev;
>>>> +	sd->internal_ops = &dw_hdmi_internal_ops;
>>>> +	sd->flags |= V4L2_SUBDEV_FL_HAS_EVENTS;
>>> Don't you also need V4L2_SUBDEV_FL_HAS_DEVNODE flag set?
>> Ouch. Yes I need otherwise the subdev will not be associated with
>> the v4l2_device.
> This flag indicates that the v4l2 subdev device node (/dev/v4l-subdev?)
> should be created for this subdevice.

Ok, will add for controller driver only then: I think for phy
this should not be added because controller is responsible to
manage phy entirely so creating a /dev/ which can be seen by
userspace can lead to confusion, maybe?

Best regards,
Jose Miguel Abreu

>
> ---
> Regards,
> Sylwester
>  

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