Re: [PATCH v2 6/6] media: adv748x: Implement TX link_setup callback

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

On 09/01/2019 00:15, Laurent Pinchart wrote:
> Hello,
> 
> On Monday, 7 January 2019 14:36:28 EET Kieran Bingham wrote:
>> On 06/01/2019 15:54, Jacopo Mondi wrote:
>>> When the adv748x driver is informed about a link being created from HDMI
>>> or AFE to a CSI-2 TX output, the 'link_setup()' callback is invoked. Make
>>> sure to implement proper routing management at link setup time, to route
>>> the selected video stream to the desired TX output.
>>
>> Overall this looks like the right approach - but I feel like the
>> handling of the io10 register might need some consideration, because
>> it's value depends on the condition of both CSI2 transmitters, not just
>> the currently parsed link.
>>
>> I had a go at some pseudo - uncompiled/untested code inline as a suggestion.
>>
>> If you think it's better - feel free to rework it in ... or not as you
>> see fit.
>>
>>> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
>>> ---
>>>
>>>  drivers/media/i2c/adv748x/adv748x-core.c | 57 +++++++++++++++++++++++-
>>>  drivers/media/i2c/adv748x/adv748x.h      |  2 +
>>>  2 files changed, 58 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/media/i2c/adv748x/adv748x-core.c
>>> b/drivers/media/i2c/adv748x/adv748x-core.c index
>>> 200e00f93546..a586bf393558 100644
>>> --- a/drivers/media/i2c/adv748x/adv748x-core.c
>>> +++ b/drivers/media/i2c/adv748x/adv748x-core.c
>>> @@ -335,6 +335,60 @@ int adv748x_tx_power(struct adv748x_csi2 *tx, bool
>>> on)
>>>  /* ----------------------------------------------------------------------
>>>   * Media Operations
>>>   */
>>> +static int adv748x_link_setup(struct media_entity *entity,
>>> +			      const struct media_pad *local,
>>> +			      const struct media_pad *remote, u32 flags)
>>> +{
>>> +	struct v4l2_subdev *rsd = media_entity_to_v4l2_subdev(remote->entity);
>>> +	struct v4l2_subdev *sd = media_entity_to_v4l2_subdev(entity);
>>> +	struct adv748x_state *state = v4l2_get_subdevdata(sd);
>>> +	struct adv748x_csi2 *tx = adv748x_sd_to_csi2(sd);
>>> +	bool enable = flags & MEDIA_LNK_FL_ENABLED;
>>> +	u8 io10;
>>> +
>>> +	/* Refuse to enable multiple links to the same TX at the same time. */
>>> +	if (enable && tx->src)
>>> +		return -EINVAL;
>>> +
>>> +	/* Set or clear the source (HDMI or AFE) and the current TX. */
>>> +	if (rsd == &state->afe.sd)
>>> +		state->afe.tx = enable ? tx : NULL;
>>> +	else
>>> +		state->hdmi.tx = enable ? tx : NULL;
>>> +
>>> +	tx->src = enable ? rsd : NULL;
>>> +
>>> +	if (!enable)
>>> +		return 0;
>>
>> Don't we potentially want to take any action on disable to power down
>> links below ?
>>
>>> +
>>> +	/* Change video stream routing, according to the newly enabled link. */
>>> +	io10 = io_read(state, ADV748X_IO_10);
>>> +	if (rsd == &state->afe.sd) {
>>> +		/*
>>> +		 * Set AFE->TXA routing and power off TXB if AFE goes to TXA.
>>> +		 * if AFE goes to TXB, we need both TXA and TXB powered on.
>>> +		 */
>>> +		io10 &= ~ADV748X_IO_10_CSI1_EN;
>>> +		io10 &= ~ADV748X_IO_10_CSI4_IN_SEL_AFE;
>>> +		if (is_txa(tx))
>>> +			io10 |= ADV748X_IO_10_CSI4_IN_SEL_AFE;
>>
>> Shouldn't the CSI4 be enabled here too? or are we assuming it's already
>> (/always) enabled?
>> 		io10 |= ADV748X_IO_10_CSI4_EN;
>>
>>> +		else
>>> +			io10 |= ADV748X_IO_10_CSI4_EN |
>>> +				ADV748X_IO_10_CSI1_EN;
>>> +	} else {
>>> +		/* Clear AFE->TXA routing and power up TXA. */
>>> +		io10 &= ~ADV748X_IO_10_CSI4_IN_SEL_AFE;
>>> +		io10 |= ADV748X_IO_10_CSI4_EN;
>>
>> But if we assume it's already enabled ... do we need this?
>> Perhaps it might be better to be explicit on this?
>>
>>> +	}
>>> +	io_write(state, ADV748X_IO_10, io10);
>>
>> Would it be any cleaner to use io_clrset() here?
>>
>> Hrm ... also it feels like this register really should be set depending
>> upon the complete state of ... &state->...
>>
>> So perhaps it deserves it's own function which should be called after
>> csi_registered() callback and any link change.
>>
>> /me has a quick go at some psuedo codeishness...:
>>
>> int adv74x_io_10(struct adv748x_state *state);
>> 	u8 bits = 0;
>> 	u8 mask = ADV748X_IO_10_CSI1_EN
>>
>> 		| ADV748X_IO_10_CSI4_EN
>> 		| ADV748X_IO_10_CSI4_IN_SEL_AFE;
>>
>> 	if (state->afe.tx) {
>> 		/* AFE Requires TXA enabled, even when output to TXB */
>> 		bits |= ADV748X_IO_10_CSI4_EN;
>>
>> 		if (is_txa(state->afe.tx))
>> 			bits |= ADV748X_IO_10_CSI4_IN_SEL_AFE
>> 		else
>> 			bits |= ADV748X_IO_10_CSI1_EN;
>> 	}
>>
>> 	if (state->hdmi.tx) {
>> 		bits |= ADV748X_IO_10_CSI4_EN;
>> 	}
>>
>> 	return io_clrset(state, ADV748X_IO_10, mask, bits);
>> }
>>
>> How does that look ? (is it even correct first?)
>>
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static const struct media_entity_operations adv748x_tx_media_ops = {
>>> +	.link_setup	= adv748x_link_setup,
>>> +	.link_validate	= v4l2_subdev_link_validate,
>>> +};
>>>
>>>  static const struct media_entity_operations adv748x_media_ops = {
>>>  	.link_validate = v4l2_subdev_link_validate,
>>> @@ -516,7 +570,8 @@ void adv748x_subdev_init(struct v4l2_subdev *sd,
>>> struct adv748x_state *state,
>>>  		state->client->addr, ident);
>>>  	
>>>  	sd->entity.function = function;
>>> -	sd->entity.ops = &adv748x_media_ops;
>>> +	sd->entity.ops = is_tx(adv748x_sd_to_csi2(sd)) ?
>>> +			 &adv748x_tx_media_ops : &adv748x_media_ops;
>>
>> Aha - yes that's a neat solution to ensure that only the TX links
>> generate link_setup calls :)
> 
> Another option would be to bail out from adv748x_link_setup() if the entity is 
> not a TX*.
> 

I suggested this in v1 - but Jacopo objected with the following:

> Checking for is_txa() and is_txb() would require to call
> 'adv_sd_to_csi2(sd)' before having made sure the 'sd' actually
> represent a csi2_tx. I would keep it as it is.

Now I look at the implementation here, I see this is precisely what it
is doing anyway .... still converting through adv748x_sd_to_csi2(sd) on
an unknown pointer type
 (which I still believe is a valid thing to do in this instance)

So yes, I think this would be simpler having the check at the top of the
adv748x_link_setup() call, and thus then there is no need to add a
second adv_media_ops structure.


>>>  }
> 
> [snip]
> 

-- 
Regards
--
Kieran