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

From: Kieran Bingham <kieran.bingham@ideasonboard.com>
To: Jacopo Mondi <jacopo+renesas@jmondi.org>,
	laurent.pinchart@ideasonboard.com,
	niklas.soderlund+renesas@ragnatech.se
Cc: linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH v2 6/6] media: adv748x: Implement TX link_setup callback
Date: Mon, 7 Jan 2019 12:36:28 +0000	[thread overview]
Message-ID: <9f156850-14b6-3ca2-47c1-e03e1bc2c0f8@ideasonboard.com> (raw)
In-Reply-To: <20190106155413.30666-7-jacopo+renesas@jmondi.org>

Hi Jacopo,

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.

Regards

Kieran

> 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 :)

>  }
>  
>  static int adv748x_parse_csi2_lanes(struct adv748x_state *state,
> diff --git a/drivers/media/i2c/adv748x/adv748x.h b/drivers/media/i2c/adv748x/adv748x.h
> index 6eb2e4a95eed..eb19c6cbbb4e 100644
> --- a/drivers/media/i2c/adv748x/adv748x.h
> +++ b/drivers/media/i2c/adv748x/adv748x.h
> @@ -93,6 +93,7 @@ struct adv748x_csi2 {
>  
>  #define is_tx_enabled(_tx) ((_tx)->state->endpoints[(_tx)->port] != NULL)
>  #define __is_tx(_tx, _ab) ((_tx) == &(_tx)->state->tx##_ab)
> +#define is_tx(_tx) (is_txa(_tx) || is_txb(_tx))
>  #define is_txa(_tx) __is_tx(_tx, a)
>  #define is_txb(_tx) __is_tx(_tx, b)
>  
> @@ -224,6 +225,7 @@ struct adv748x_state {
>  #define ADV748X_IO_10_CSI4_EN		BIT(7)
>  #define ADV748X_IO_10_CSI1_EN		BIT(6)
>  #define ADV748X_IO_10_PIX_OUT_EN	BIT(5)
> +#define ADV748X_IO_10_CSI4_IN_SEL_AFE	BIT(3)

>  
>  #define ADV748X_IO_CHIP_REV_ID_1	0xdf
>  #define ADV748X_IO_CHIP_REV_ID_2	0xe0
> 

-- 
Regards
--
Kieran