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

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

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*.

> >  }

[snip]

-- 
Regards,

Laurent Pinchart