linux-kernel - Re: [PATCH v2 3/3] media: dt-bindings: vpif: new optional property

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Message-ID: <2aeaecfd-b3a8-99a8-0530-9d221a9127dd@ti.com>
Date:   Wed, 1 Mar 2017 18:46:56 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
CC:     Rob Herring <robh@...nel.org>,
        David Lechner <david@...hnology.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Patrick Titiano <ptitiano@...libre.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mark Rutland <mark.rutland@....com>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] media: dt-bindings: vpif: new optional property

On Tuesday 28 February 2017 04:30 PM, Bartosz Golaszewski wrote:
> 2017-02-28 6:36 GMT+01:00 Sekhar Nori <nsekhar@...com>:
>> On Tuesday 28 February 2017 04:22 AM, Rob Herring wrote:
>>> On Wed, Feb 22, 2017 at 02:43:47PM +0100, Bartosz Golaszewski wrote:
>>>> Add an optional property - enable-gpios - which can be used to specify
>>>> the GPIOs that must be requested to select the vpif functionality.
>>>>
>>>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>> ---
>>>>  Documentation/devicetree/bindings/media/ti,da850-vpif.txt | 7 +++++++
>>>>  1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/media/ti,da850-vpif.txt b/Documentation/devicetree/bindings/media/ti,da850-vpif.txt
>>>> index df7182a..23c5405 100644
>>>> --- a/Documentation/devicetree/bindings/media/ti,da850-vpif.txt
>>>> +++ b/Documentation/devicetree/bindings/media/ti,da850-vpif.txt
>>>> @@ -13,6 +13,9 @@ Required properties:
>>>>  - reg: physical base address and length of the registers set for the device;
>>>>  - interrupts: should contain IRQ line for the VPIF
>>>>
>>>> +Optional properties:
>>>> +- enable-gpios: phandle of the GPIOs used to select the vpif functionality
>>>
>>> What does this control exactly? The GPIOs belong in the node they are
>>> connected to and having GPIOs routed to this block seems strange.
>>
>> The DA850 EVM board implements on-board muxing which lets the video
>> input (via VPIF) to be routed to a TVP5147 (video decoder) for composite
>> input or to a camera header. There are other mux options which use the
>> same VPIF SoC pins (RMII ethernet or character LCD).
>>
>> There is a three-to-eight demux on the board which drives enable signals
>> to buffers letting you choose from these options.
>>
>> From your response, it looks like you want the enable-gpios property to
>> be in the TVP5147 or camera node. That does make sense to me.
>>
> 
> Wouldn't that cause races again? The TVP5147 ADC is probed from within
> the vpif driver as a media subdev (after initialize_vpif(),
> v4l2_device_register(), irq requests etc.).

When TVP5147 probe fails with -EPROBE_DEFER, I assume the error can
propagate back to vpif_probe() which would then de-register the V4L2
device as part of probe error unwinding. That should then allow the
probe to be retried at a later time.

Thanks,
Sekhar

> 
> Thanks,
> Bartosz
>